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android-kvm / linux / fe95f58320e6c8dcea3bcb01336b9a7fdd7f684b / . / arch / x86 / kvm / mmu / mmu.c
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// SPDX-License-Identifier: GPL-2.0-only
/*
* Kernel-based Virtual Machine driver for Linux
*
* This module enables machines with Intel VT-x extensions to run virtual
* machines without emulation or binary translation.
*
* MMU support
*
* Copyright (C) 2006 Qumranet, Inc.
* Copyright 2010 Red Hat, Inc. and/or its affiliates.
*
* Authors:
* Yaniv Kamay <yaniv@qumranet.com>
* Avi Kivity <avi@qumranet.com>
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include "irq.h"
#include "ioapic.h"
#include "mmu.h"
#include "mmu_internal.h"
#include "tdp_mmu.h"
#include "x86.h"
#include "kvm_cache_regs.h"
#include "smm.h"
#include "kvm_emulate.h"
#include "page_track.h"
#include "cpuid.h"
#include "spte.h"
#include <linux/kvm_host.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/moduleparam.h>
#include <linux/export.h>
#include <linux/swap.h>
#include <linux/hugetlb.h>
#include <linux/compiler.h>
#include <linux/srcu.h>
#include <linux/slab.h>
#include <linux/sched/signal.h>
#include <linux/uaccess.h>
#include <linux/hash.h>
#include <linux/kern_levels.h>
#include <linux/kstrtox.h>
#include <linux/kthread.h>
#include <linux/wordpart.h>
#include <asm/page.h>
#include <asm/memtype.h>
#include <asm/cmpxchg.h>
#include <asm/io.h>
#include <asm/set_memory.h>
#include <asm/spec-ctrl.h>
#include <asm/vmx.h>
#include "trace.h"
static bool nx_hugepage_mitigation_hard_disabled;
int __read_mostly nx_huge_pages = -1;
static uint __read_mostly nx_huge_pages_recovery_period_ms;
#ifdef CONFIG_PREEMPT_RT
/* Recovery can cause latency spikes, disable it for PREEMPT_RT. */
static uint __read_mostly nx_huge_pages_recovery_ratio = 0;
#else
static uint __read_mostly nx_huge_pages_recovery_ratio = 60;
#endif
static int get_nx_huge_pages(char *buffer, const struct kernel_param *kp);
static int set_nx_huge_pages(const char *val, const struct kernel_param *kp);
static int set_nx_huge_pages_recovery_param(const char *val, const struct kernel_param *kp);
static const struct kernel_param_ops nx_huge_pages_ops = {
.set = set_nx_huge_pages,
.get = get_nx_huge_pages,
};
static const struct kernel_param_ops nx_huge_pages_recovery_param_ops = {
.set = set_nx_huge_pages_recovery_param,
.get = param_get_uint,
};
module_param_cb(nx_huge_pages, &nx_huge_pages_ops, &nx_huge_pages, 0644);
__MODULE_PARM_TYPE(nx_huge_pages, "bool");
module_param_cb(nx_huge_pages_recovery_ratio, &nx_huge_pages_recovery_param_ops,
&nx_huge_pages_recovery_ratio, 0644);
__MODULE_PARM_TYPE(nx_huge_pages_recovery_ratio, "uint");
module_param_cb(nx_huge_pages_recovery_period_ms, &nx_huge_pages_recovery_param_ops,
&nx_huge_pages_recovery_period_ms, 0644);
__MODULE_PARM_TYPE(nx_huge_pages_recovery_period_ms, "uint");
static bool __read_mostly force_flush_and_sync_on_reuse;
module_param_named(flush_on_reuse, force_flush_and_sync_on_reuse, bool, 0644);
/*
* When setting this variable to true it enables Two-Dimensional-Paging
* where the hardware walks 2 page tables:
* 1. the guest-virtual to guest-physical
* 2. while doing 1. it walks guest-physical to host-physical
* If the hardware supports that we don't need to do shadow paging.
*/
bool tdp_enabled = false;
static bool __ro_after_init tdp_mmu_allowed;
#ifdef CONFIG_X86_64
bool __read_mostly tdp_mmu_enabled = true;
module_param_named(tdp_mmu, tdp_mmu_enabled, bool, 0444);
#endif
static int max_huge_page_level __read_mostly;
static int tdp_root_level __read_mostly;
static int max_tdp_level __read_mostly;
#define PTE_PREFETCH_NUM 8
#include <trace/events/kvm.h>
/* make pte_list_desc fit well in cache lines */
#define PTE_LIST_EXT 14
/*
* struct pte_list_desc is the core data structure used to implement a custom
* list for tracking a set of related SPTEs, e.g. all the SPTEs that map a
* given GFN when used in the context of rmaps. Using a custom list allows KVM
* to optimize for the common case where many GFNs will have at most a handful
* of SPTEs pointing at them, i.e. allows packing multiple SPTEs into a small
* memory footprint, which in turn improves runtime performance by exploiting
* cache locality.
*
* A list is comprised of one or more pte_list_desc objects (descriptors).
* Each individual descriptor stores up to PTE_LIST_EXT SPTEs. If a descriptor
* is full and a new SPTEs needs to be added, a new descriptor is allocated and
* becomes the head of the list. This means that by definitions, all tail
* descriptors are full.
*
* Note, the meta data fields are deliberately placed at the start of the
* structure to optimize the cacheline layout; accessing the descriptor will
* touch only a single cacheline so long as @spte_count<=6 (or if only the
* descriptors metadata is accessed).
*/
struct pte_list_desc {
struct pte_list_desc *more;
/* The number of PTEs stored in _this_ descriptor. */
u32 spte_count;
/* The number of PTEs stored in all tails of this descriptor. */
u32 tail_count;
u64 *sptes[PTE_LIST_EXT];
};
struct kvm_shadow_walk_iterator {
u64 addr;
hpa_t shadow_addr;
u64 *sptep;
int level;
unsigned index;
};
#define for_each_shadow_entry_using_root(_vcpu, _root, _addr, _walker) \
for (shadow_walk_init_using_root(&(_walker), (_vcpu), \
(_root), (_addr)); \
shadow_walk_okay(&(_walker)); \
shadow_walk_next(&(_walker)))
#define for_each_shadow_entry(_vcpu, _addr, _walker) \
for (shadow_walk_init(&(_walker), _vcpu, _addr); \
shadow_walk_okay(&(_walker)); \
shadow_walk_next(&(_walker)))
#define for_each_shadow_entry_lockless(_vcpu, _addr, _walker, spte) \
for (shadow_walk_init(&(_walker), _vcpu, _addr); \
shadow_walk_okay(&(_walker)) && \
({ spte = mmu_spte_get_lockless(_walker.sptep); 1; }); \
__shadow_walk_next(&(_walker), spte))
static struct kmem_cache *pte_list_desc_cache;
struct kmem_cache *mmu_page_header_cache;
static struct percpu_counter kvm_total_used_mmu_pages;
static void mmu_spte_set(u64 *sptep, u64 spte);
struct kvm_mmu_role_regs {
const unsigned long cr0;
const unsigned long cr4;
const u64 efer;
};
#define CREATE_TRACE_POINTS
#include "mmutrace.h"
/*
* Yes, lot's of underscores. They're a hint that you probably shouldn't be
* reading from the role_regs. Once the root_role is constructed, it becomes
* the single source of truth for the MMU's state.
*/
#define BUILD_MMU_ROLE_REGS_ACCESSOR(reg, name, flag) \
static inline bool __maybe_unused \
____is_##reg##_##name(const struct kvm_mmu_role_regs *regs) \
{ \
return !!(regs->reg & flag); \
}
BUILD_MMU_ROLE_REGS_ACCESSOR(cr0, pg, X86_CR0_PG);
BUILD_MMU_ROLE_REGS_ACCESSOR(cr0, wp, X86_CR0_WP);
BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, pse, X86_CR4_PSE);
BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, pae, X86_CR4_PAE);
BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, smep, X86_CR4_SMEP);
BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, smap, X86_CR4_SMAP);
BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, pke, X86_CR4_PKE);
BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, la57, X86_CR4_LA57);
BUILD_MMU_ROLE_REGS_ACCESSOR(efer, nx, EFER_NX);
BUILD_MMU_ROLE_REGS_ACCESSOR(efer, lma, EFER_LMA);
/*
* The MMU itself (with a valid role) is the single source of truth for the
* MMU. Do not use the regs used to build the MMU/role, nor the vCPU. The
* regs don't account for dependencies, e.g. clearing CR4 bits if CR0.PG=1,
* and the vCPU may be incorrect/irrelevant.
*/
#define BUILD_MMU_ROLE_ACCESSOR(base_or_ext, reg, name) \
static inline bool __maybe_unused is_##reg##_##name(struct kvm_mmu *mmu) \
{ \
return !!(mmu->cpu_role. base_or_ext . reg##_##name); \
}
BUILD_MMU_ROLE_ACCESSOR(base, cr0, wp);
BUILD_MMU_ROLE_ACCESSOR(ext, cr4, pse);
BUILD_MMU_ROLE_ACCESSOR(ext, cr4, smep);
BUILD_MMU_ROLE_ACCESSOR(ext, cr4, smap);
BUILD_MMU_ROLE_ACCESSOR(ext, cr4, pke);
BUILD_MMU_ROLE_ACCESSOR(ext, cr4, la57);
BUILD_MMU_ROLE_ACCESSOR(base, efer, nx);
BUILD_MMU_ROLE_ACCESSOR(ext, efer, lma);
static inline bool is_cr0_pg(struct kvm_mmu *mmu)
{
return mmu->cpu_role.base.level > 0;
}
static inline bool is_cr4_pae(struct kvm_mmu *mmu)
{
return !mmu->cpu_role.base.has_4_byte_gpte;
}
static struct kvm_mmu_role_regs vcpu_to_role_regs(struct kvm_vcpu *vcpu)
{
struct kvm_mmu_role_regs regs = {
.cr0 = kvm_read_cr0_bits(vcpu, KVM_MMU_CR0_ROLE_BITS),
.cr4 = kvm_read_cr4_bits(vcpu, KVM_MMU_CR4_ROLE_BITS),
.efer = vcpu->arch.efer,
};
return regs;
}
static unsigned long get_guest_cr3(struct kvm_vcpu *vcpu)
{
return kvm_read_cr3(vcpu);
}
static inline unsigned long kvm_mmu_get_guest_pgd(struct kvm_vcpu *vcpu,
struct kvm_mmu *mmu)
{
if (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) && mmu->get_guest_pgd == get_guest_cr3)
return kvm_read_cr3(vcpu);
return mmu->get_guest_pgd(vcpu);
}
static inline bool kvm_available_flush_remote_tlbs_range(void)
{
#if IS_ENABLED(CONFIG_HYPERV)
return kvm_x86_ops.flush_remote_tlbs_range;
#else
return false;
#endif
}
static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index);
/* Flush the range of guest memory mapped by the given SPTE. */
static void kvm_flush_remote_tlbs_sptep(struct kvm *kvm, u64 *sptep)
{
struct kvm_mmu_page *sp = sptep_to_sp(sptep);
gfn_t gfn = kvm_mmu_page_get_gfn(sp, spte_index(sptep));
kvm_flush_remote_tlbs_gfn(kvm, gfn, sp->role.level);
}
static void mark_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, u64 gfn,
unsigned int access)
{
u64 spte = make_mmio_spte(vcpu, gfn, access);
trace_mark_mmio_spte(sptep, gfn, spte);
mmu_spte_set(sptep, spte);
}
static gfn_t get_mmio_spte_gfn(u64 spte)
{
u64 gpa = spte & shadow_nonpresent_or_rsvd_lower_gfn_mask;
gpa |= (spte >> SHADOW_NONPRESENT_OR_RSVD_MASK_LEN)
& shadow_nonpresent_or_rsvd_mask;
return gpa >> PAGE_SHIFT;
}
static unsigned get_mmio_spte_access(u64 spte)
{
return spte & shadow_mmio_access_mask;
}
static bool check_mmio_spte(struct kvm_vcpu *vcpu, u64 spte)
{
u64 kvm_gen, spte_gen, gen;
gen = kvm_vcpu_memslots(vcpu)->generation;
if (unlikely(gen & KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS))
return false;
kvm_gen = gen & MMIO_SPTE_GEN_MASK;
spte_gen = get_mmio_spte_generation(spte);
trace_check_mmio_spte(spte, kvm_gen, spte_gen);
return likely(kvm_gen == spte_gen);
}
static int is_cpuid_PSE36(void)
{
return 1;
}
#ifdef CONFIG_X86_64
static void __set_spte(u64 *sptep, u64 spte)
{
KVM_MMU_WARN_ON(is_ept_ve_possible(spte));
WRITE_ONCE(*sptep, spte);
}
static void __update_clear_spte_fast(u64 *sptep, u64 spte)
{
KVM_MMU_WARN_ON(is_ept_ve_possible(spte));
WRITE_ONCE(*sptep, spte);
}
static u64 __update_clear_spte_slow(u64 *sptep, u64 spte)
{
KVM_MMU_WARN_ON(is_ept_ve_possible(spte));
return xchg(sptep, spte);
}
static u64 __get_spte_lockless(u64 *sptep)
{
return READ_ONCE(*sptep);
}
#else
union split_spte {
struct {
u32 spte_low;
u32 spte_high;
};
u64 spte;
};
static void count_spte_clear(u64 *sptep, u64 spte)
{
struct kvm_mmu_page *sp = sptep_to_sp(sptep);
if (is_shadow_present_pte(spte))
return;
/* Ensure the spte is completely set before we increase the count */
smp_wmb();
sp->clear_spte_count++;
}
static void __set_spte(u64 *sptep, u64 spte)
{
union split_spte *ssptep, sspte;
ssptep = (union split_spte *)sptep;
sspte = (union split_spte)spte;
ssptep->spte_high = sspte.spte_high;
/*
* If we map the spte from nonpresent to present, We should store
* the high bits firstly, then set present bit, so cpu can not
* fetch this spte while we are setting the spte.
*/
smp_wmb();
WRITE_ONCE(ssptep->spte_low, sspte.spte_low);
}
static void __update_clear_spte_fast(u64 *sptep, u64 spte)
{
union split_spte *ssptep, sspte;
ssptep = (union split_spte *)sptep;
sspte = (union split_spte)spte;
WRITE_ONCE(ssptep->spte_low, sspte.spte_low);
/*
* If we map the spte from present to nonpresent, we should clear
* present bit firstly to avoid vcpu fetch the old high bits.
*/
smp_wmb();
ssptep->spte_high = sspte.spte_high;
count_spte_clear(sptep, spte);
}
static u64 __update_clear_spte_slow(u64 *sptep, u64 spte)
{
union split_spte *ssptep, sspte, orig;
ssptep = (union split_spte *)sptep;
sspte = (union split_spte)spte;
/* xchg acts as a barrier before the setting of the high bits */
orig.spte_low = xchg(&ssptep->spte_low, sspte.spte_low);
orig.spte_high = ssptep->spte_high;
ssptep->spte_high = sspte.spte_high;
count_spte_clear(sptep, spte);
return orig.spte;
}
/*
* The idea using the light way get the spte on x86_32 guest is from
* gup_get_pte (mm/gup.c).
*
* An spte tlb flush may be pending, because they are coalesced and
* we are running out of the MMU lock. Therefore
* we need to protect against in-progress updates of the spte.
*
* Reading the spte while an update is in progress may get the old value
* for the high part of the spte. The race is fine for a present->non-present
* change (because the high part of the spte is ignored for non-present spte),
* but for a present->present change we must reread the spte.
*
* All such changes are done in two steps (present->non-present and
* non-present->present), hence it is enough to count the number of
* present->non-present updates: if it changed while reading the spte,
* we might have hit the race. This is done using clear_spte_count.
*/
static u64 __get_spte_lockless(u64 *sptep)
{
struct kvm_mmu_page *sp = sptep_to_sp(sptep);
union split_spte spte, *orig = (union split_spte *)sptep;
int count;
retry:
count = sp->clear_spte_count;
smp_rmb();
spte.spte_low = orig->spte_low;
smp_rmb();
spte.spte_high = orig->spte_high;
smp_rmb();
if (unlikely(spte.spte_low != orig->spte_low ||
count != sp->clear_spte_count))
goto retry;
return spte.spte;
}
#endif
/* Rules for using mmu_spte_set:
* Set the sptep from nonpresent to present.
* Note: the sptep being assigned *must* be either not present
* or in a state where the hardware will not attempt to update
* the spte.
*/
static void mmu_spte_set(u64 *sptep, u64 new_spte)
{
WARN_ON_ONCE(is_shadow_present_pte(*sptep));
__set_spte(sptep, new_spte);
}
/*
* Update the SPTE (excluding the PFN), but do not track changes in its
* accessed/dirty status.
*/
static u64 mmu_spte_update_no_track(u64 *sptep, u64 new_spte)
{
u64 old_spte = *sptep;
WARN_ON_ONCE(!is_shadow_present_pte(new_spte));
check_spte_writable_invariants(new_spte);
if (!is_shadow_present_pte(old_spte)) {
mmu_spte_set(sptep, new_spte);
return old_spte;
}
if (!spte_has_volatile_bits(old_spte))
__update_clear_spte_fast(sptep, new_spte);
else
old_spte = __update_clear_spte_slow(sptep, new_spte);
WARN_ON_ONCE(spte_to_pfn(old_spte) != spte_to_pfn(new_spte));
return old_spte;
}
/* Rules for using mmu_spte_update:
* Update the state bits, it means the mapped pfn is not changed.
*
* Whenever an MMU-writable SPTE is overwritten with a read-only SPTE, remote
* TLBs must be flushed. Otherwise rmap_write_protect will find a read-only
* spte, even though the writable spte might be cached on a CPU's TLB.
*
* Returns true if the TLB needs to be flushed
*/
static bool mmu_spte_update(u64 *sptep, u64 new_spte)
{
bool flush = false;
u64 old_spte = mmu_spte_update_no_track(sptep, new_spte);
if (!is_shadow_present_pte(old_spte))
return false;
/*
* For the spte updated out of mmu-lock is safe, since
* we always atomically update it, see the comments in
* spte_has_volatile_bits().
*/
if (is_mmu_writable_spte(old_spte) &&
!is_writable_pte(new_spte))
flush = true;
/*
* Flush TLB when accessed/dirty states are changed in the page tables,
* to guarantee consistency between TLB and page tables.
*/
if (is_accessed_spte(old_spte) && !is_accessed_spte(new_spte)) {
flush = true;
kvm_set_pfn_accessed(spte_to_pfn(old_spte));
}
if (is_dirty_spte(old_spte) && !is_dirty_spte(new_spte)) {
flush = true;
kvm_set_pfn_dirty(spte_to_pfn(old_spte));
}
return flush;
}
/*
* Rules for using mmu_spte_clear_track_bits:
* It sets the sptep from present to nonpresent, and track the
* state bits, it is used to clear the last level sptep.
* Returns the old PTE.
*/
static u64 mmu_spte_clear_track_bits(struct kvm *kvm, u64 *sptep)
{
kvm_pfn_t pfn;
u64 old_spte = *sptep;
int level = sptep_to_sp(sptep)->role.level;
struct page *page;
if (!is_shadow_present_pte(old_spte) ||
!spte_has_volatile_bits(old_spte))
__update_clear_spte_fast(sptep, SHADOW_NONPRESENT_VALUE);
else
old_spte = __update_clear_spte_slow(sptep, SHADOW_NONPRESENT_VALUE);
if (!is_shadow_present_pte(old_spte))
return old_spte;
kvm_update_page_stats(kvm, level, -1);
pfn = spte_to_pfn(old_spte);
/*
* KVM doesn't hold a reference to any pages mapped into the guest, and
* instead uses the mmu_notifier to ensure that KVM unmaps any pages
* before they are reclaimed. Sanity check that, if the pfn is backed
* by a refcounted page, the refcount is elevated.
*/
page = kvm_pfn_to_refcounted_page(pfn);
WARN_ON_ONCE(page && !page_count(page));
if (is_accessed_spte(old_spte))
kvm_set_pfn_accessed(pfn);
if (is_dirty_spte(old_spte))
kvm_set_pfn_dirty(pfn);
return old_spte;
}
/*
* Rules for using mmu_spte_clear_no_track:
* Directly clear spte without caring the state bits of sptep,
* it is used to set the upper level spte.
*/
static void mmu_spte_clear_no_track(u64 *sptep)
{
__update_clear_spte_fast(sptep, SHADOW_NONPRESENT_VALUE);
}
static u64 mmu_spte_get_lockless(u64 *sptep)
{
return __get_spte_lockless(sptep);
}
static inline bool is_tdp_mmu_active(struct kvm_vcpu *vcpu)
{
return tdp_mmu_enabled && vcpu->arch.mmu->root_role.direct;
}
static void walk_shadow_page_lockless_begin(struct kvm_vcpu *vcpu)
{
if (is_tdp_mmu_active(vcpu)) {
kvm_tdp_mmu_walk_lockless_begin();
} else {
/*
* Prevent page table teardown by making any free-er wait during
* kvm_flush_remote_tlbs() IPI to all active vcpus.
*/
local_irq_disable();
/*
* Make sure a following spte read is not reordered ahead of the write
* to vcpu->mode.
*/
smp_store_mb(vcpu->mode, READING_SHADOW_PAGE_TABLES);
}
}
static void walk_shadow_page_lockless_end(struct kvm_vcpu *vcpu)
{
if (is_tdp_mmu_active(vcpu)) {
kvm_tdp_mmu_walk_lockless_end();
} else {
/*
* Make sure the write to vcpu->mode is not reordered in front of
* reads to sptes. If it does, kvm_mmu_commit_zap_page() can see us
* OUTSIDE_GUEST_MODE and proceed to free the shadow page table.
*/
smp_store_release(&vcpu->mode, OUTSIDE_GUEST_MODE);
local_irq_enable();
}
}
static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu, bool maybe_indirect)
{
int r;
/* 1 rmap, 1 parent PTE per level, and the prefetched rmaps. */
r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache,
1 + PT64_ROOT_MAX_LEVEL + PTE_PREFETCH_NUM);
if (r)
return r;
r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_shadow_page_cache,
PT64_ROOT_MAX_LEVEL);
if (r)
return r;
if (maybe_indirect) {
r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_shadowed_info_cache,
PT64_ROOT_MAX_LEVEL);
if (r)
return r;
}
return kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_page_header_cache,
PT64_ROOT_MAX_LEVEL);
}
static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
{
kvm_mmu_free_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache);
kvm_mmu_free_memory_cache(&vcpu->arch.mmu_shadow_page_cache);
kvm_mmu_free_memory_cache(&vcpu->arch.mmu_shadowed_info_cache);
kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_header_cache);
}
static void mmu_free_pte_list_desc(struct pte_list_desc *pte_list_desc)
{
kmem_cache_free(pte_list_desc_cache, pte_list_desc);
}
static bool sp_has_gptes(struct kvm_mmu_page *sp);
static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index)
{
if (sp->role.passthrough)
return sp->gfn;
if (sp->shadowed_translation)
return sp->shadowed_translation[index] >> PAGE_SHIFT;
return sp->gfn + (index << ((sp->role.level - 1) * SPTE_LEVEL_BITS));
}
/*
* For leaf SPTEs, fetch the *guest* access permissions being shadowed. Note
* that the SPTE itself may have a more constrained access permissions that
* what the guest enforces. For example, a guest may create an executable
* huge PTE but KVM may disallow execution to mitigate iTLB multihit.
*/
static u32 kvm_mmu_page_get_access(struct kvm_mmu_page *sp, int index)
{
if (sp->shadowed_translation)
return sp->shadowed_translation[index] & ACC_ALL;
/*
* For direct MMUs (e.g. TDP or non-paging guests) or passthrough SPs,
* KVM is not shadowing any guest page tables, so the "guest access
* permissions" are just ACC_ALL.
*
* For direct SPs in indirect MMUs (shadow paging), i.e. when KVM
* is shadowing a guest huge page with small pages, the guest access
* permissions being shadowed are the access permissions of the huge
* page.
*
* In both cases, sp->role.access contains the correct access bits.
*/
return sp->role.access;
}
static void kvm_mmu_page_set_translation(struct kvm_mmu_page *sp, int index,
gfn_t gfn, unsigned int access)
{
if (sp->shadowed_translation) {
sp->shadowed_translation[index] = (gfn << PAGE_SHIFT) | access;
return;
}
WARN_ONCE(access != kvm_mmu_page_get_access(sp, index),
"access mismatch under %s page %llx (expected %u, got %u)\n",
sp->role.passthrough ? "passthrough" : "direct",
sp->gfn, kvm_mmu_page_get_access(sp, index), access);
WARN_ONCE(gfn != kvm_mmu_page_get_gfn(sp, index),
"gfn mismatch under %s page %llx (expected %llx, got %llx)\n",
sp->role.passthrough ? "passthrough" : "direct",
sp->gfn, kvm_mmu_page_get_gfn(sp, index), gfn);
}
static void kvm_mmu_page_set_access(struct kvm_mmu_page *sp, int index,
unsigned int access)
{
gfn_t gfn = kvm_mmu_page_get_gfn(sp, index);
kvm_mmu_page_set_translation(sp, index, gfn, access);
}
/*
* Return the pointer to the large page information for a given gfn,
* handling slots that are not large page aligned.
*/
static struct kvm_lpage_info *lpage_info_slot(gfn_t gfn,
const struct kvm_memory_slot *slot, int level)
{
unsigned long idx;
idx = gfn_to_index(gfn, slot->base_gfn, level);
return &slot->arch.lpage_info[level - 2][idx];
}
/*
* The most significant bit in disallow_lpage tracks whether or not memory
* attributes are mixed, i.e. not identical for all gfns at the current level.
* The lower order bits are used to refcount other cases where a hugepage is
* disallowed, e.g. if KVM has shadow a page table at the gfn.
*/
#define KVM_LPAGE_MIXED_FLAG BIT(31)
static void update_gfn_disallow_lpage_count(const struct kvm_memory_slot *slot,
gfn_t gfn, int count)
{
struct kvm_lpage_info *linfo;
int old, i;
for (i = PG_LEVEL_2M; i <= KVM_MAX_HUGEPAGE_LEVEL; ++i) {
linfo = lpage_info_slot(gfn, slot, i);
old = linfo->disallow_lpage;
linfo->disallow_lpage += count;
WARN_ON_ONCE((old ^ linfo->disallow_lpage) & KVM_LPAGE_MIXED_FLAG);
}
}
void kvm_mmu_gfn_disallow_lpage(const struct kvm_memory_slot *slot, gfn_t gfn)
{
update_gfn_disallow_lpage_count(slot, gfn, 1);
}
void kvm_mmu_gfn_allow_lpage(const struct kvm_memory_slot *slot, gfn_t gfn)
{
update_gfn_disallow_lpage_count(slot, gfn, -1);
}
static void account_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
{
struct kvm_memslots *slots;
struct kvm_memory_slot *slot;
gfn_t gfn;
kvm->arch.indirect_shadow_pages++;
/*
* Ensure indirect_shadow_pages is elevated prior to re-reading guest
* child PTEs in FNAME(gpte_changed), i.e. guarantee either in-flight
* emulated writes are visible before re-reading guest PTEs, or that
* an emulated write will see the elevated count and acquire mmu_lock
* to update SPTEs. Pairs with the smp_mb() in kvm_mmu_track_write().
*/
smp_mb();
gfn = sp->gfn;
slots = kvm_memslots_for_spte_role(kvm, sp->role);
slot = __gfn_to_memslot(slots, gfn);
/* the non-leaf shadow pages are keeping readonly. */
if (sp->role.level > PG_LEVEL_4K)
return __kvm_write_track_add_gfn(kvm, slot, gfn);
kvm_mmu_gfn_disallow_lpage(slot, gfn);
if (kvm_mmu_slot_gfn_write_protect(kvm, slot, gfn, PG_LEVEL_4K))
kvm_flush_remote_tlbs_gfn(kvm, gfn, PG_LEVEL_4K);
}
void track_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
/*
* If it's possible to replace the shadow page with an NX huge page,
* i.e. if the shadow page is the only thing currently preventing KVM
* from using a huge page, add the shadow page to the list of "to be
* zapped for NX recovery" pages. Note, the shadow page can already be
* on the list if KVM is reusing an existing shadow page, i.e. if KVM
* links a shadow page at multiple points.
*/
if (!list_empty(&sp->possible_nx_huge_page_link))
return;
++kvm->stat.nx_lpage_splits;
list_add_tail(&sp->possible_nx_huge_page_link,
&kvm->arch.possible_nx_huge_pages);
}
static void account_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp,
bool nx_huge_page_possible)
{
sp->nx_huge_page_disallowed = true;
if (nx_huge_page_possible)
track_possible_nx_huge_page(kvm, sp);
}
static void unaccount_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
{
struct kvm_memslots *slots;
struct kvm_memory_slot *slot;
gfn_t gfn;
kvm->arch.indirect_shadow_pages--;
gfn = sp->gfn;
slots = kvm_memslots_for_spte_role(kvm, sp->role);
slot = __gfn_to_memslot(slots, gfn);
if (sp->role.level > PG_LEVEL_4K)
return __kvm_write_track_remove_gfn(kvm, slot, gfn);
kvm_mmu_gfn_allow_lpage(slot, gfn);
}
void untrack_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
if (list_empty(&sp->possible_nx_huge_page_link))
return;
--kvm->stat.nx_lpage_splits;
list_del_init(&sp->possible_nx_huge_page_link);
}
static void unaccount_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
sp->nx_huge_page_disallowed = false;
untrack_possible_nx_huge_page(kvm, sp);
}
static struct kvm_memory_slot *gfn_to_memslot_dirty_bitmap(struct kvm_vcpu *vcpu,
gfn_t gfn,
bool no_dirty_log)
{
struct kvm_memory_slot *slot;
slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
return NULL;
if (no_dirty_log && kvm_slot_dirty_track_enabled(slot))
return NULL;
return slot;
}
/*
* About rmap_head encoding:
*
* If the bit zero of rmap_head->val is clear, then it points to the only spte
* in this rmap chain. Otherwise, (rmap_head->val & ~1) points to a struct
* pte_list_desc containing more mappings.
*/
#define KVM_RMAP_MANY BIT(0)
/*
* Returns the number of pointers in the rmap chain, not counting the new one.
*/
static int pte_list_add(struct kvm_mmu_memory_cache *cache, u64 *spte,
struct kvm_rmap_head *rmap_head)
{
struct pte_list_desc *desc;
int count = 0;
if (!rmap_head->val) {
rmap_head->val = (unsigned long)spte;
} else if (!(rmap_head->val & KVM_RMAP_MANY)) {
desc = kvm_mmu_memory_cache_alloc(cache);
desc->sptes[0] = (u64 *)rmap_head->val;
desc->sptes[1] = spte;
desc->spte_count = 2;
desc->tail_count = 0;
rmap_head->val = (unsigned long)desc | KVM_RMAP_MANY;
++count;
} else {
desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY);
count = desc->tail_count + desc->spte_count;
/*
* If the previous head is full, allocate a new head descriptor
* as tail descriptors are always kept full.
*/
if (desc->spte_count == PTE_LIST_EXT) {
desc = kvm_mmu_memory_cache_alloc(cache);
desc->more = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY);
desc->spte_count = 0;
desc->tail_count = count;
rmap_head->val = (unsigned long)desc | KVM_RMAP_MANY;
}
desc->sptes[desc->spte_count++] = spte;
}
return count;
}
static void pte_list_desc_remove_entry(struct kvm *kvm,
struct kvm_rmap_head *rmap_head,
struct pte_list_desc *desc, int i)
{
struct pte_list_desc *head_desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY);
int j = head_desc->spte_count - 1;
/*
* The head descriptor should never be empty. A new head is added only
* when adding an entry and the previous head is full, and heads are
* removed (this flow) when they become empty.
*/
KVM_BUG_ON_DATA_CORRUPTION(j < 0, kvm);
/*
* Replace the to-be-freed SPTE with the last valid entry from the head
* descriptor to ensure that tail descriptors are full at all times.
* Note, this also means that tail_count is stable for each descriptor.
*/
desc->sptes[i] = head_desc->sptes[j];
head_desc->sptes[j] = NULL;
head_desc->spte_count--;
if (head_desc->spte_count)
return;
/*
* The head descriptor is empty. If there are no tail descriptors,
* nullify the rmap head to mark the list as empty, else point the rmap
* head at the next descriptor, i.e. the new head.
*/
if (!head_desc->more)
rmap_head->val = 0;
else
rmap_head->val = (unsigned long)head_desc->more | KVM_RMAP_MANY;
mmu_free_pte_list_desc(head_desc);
}
static void pte_list_remove(struct kvm *kvm, u64 *spte,
struct kvm_rmap_head *rmap_head)
{
struct pte_list_desc *desc;
int i;
if (KVM_BUG_ON_DATA_CORRUPTION(!rmap_head->val, kvm))
return;
if (!(rmap_head->val & KVM_RMAP_MANY)) {
if (KVM_BUG_ON_DATA_CORRUPTION((u64 *)rmap_head->val != spte, kvm))
return;
rmap_head->val = 0;
} else {
desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY);
while (desc) {
for (i = 0; i < desc->spte_count; ++i) {
if (desc->sptes[i] == spte) {
pte_list_desc_remove_entry(kvm, rmap_head,
desc, i);
return;
}
}
desc = desc->more;
}
KVM_BUG_ON_DATA_CORRUPTION(true, kvm);
}
}
static void kvm_zap_one_rmap_spte(struct kvm *kvm,
struct kvm_rmap_head *rmap_head, u64 *sptep)
{
mmu_spte_clear_track_bits(kvm, sptep);
pte_list_remove(kvm, sptep, rmap_head);
}
/* Return true if at least one SPTE was zapped, false otherwise */
static bool kvm_zap_all_rmap_sptes(struct kvm *kvm,
struct kvm_rmap_head *rmap_head)
{
struct pte_list_desc *desc, *next;
int i;
if (!rmap_head->val)
return false;
if (!(rmap_head->val & KVM_RMAP_MANY)) {
mmu_spte_clear_track_bits(kvm, (u64 *)rmap_head->val);
goto out;
}
desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY);
for (; desc; desc = next) {
for (i = 0; i < desc->spte_count; i++)
mmu_spte_clear_track_bits(kvm, desc->sptes[i]);
next = desc->more;
mmu_free_pte_list_desc(desc);
}
out:
/* rmap_head is meaningless now, remember to reset it */
rmap_head->val = 0;
return true;
}
unsigned int pte_list_count(struct kvm_rmap_head *rmap_head)
{
struct pte_list_desc *desc;
if (!rmap_head->val)
return 0;
else if (!(rmap_head->val & KVM_RMAP_MANY))
return 1;
desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY);
return desc->tail_count + desc->spte_count;
}
static struct kvm_rmap_head *gfn_to_rmap(gfn_t gfn, int level,
const struct kvm_memory_slot *slot)
{
unsigned long idx;
idx = gfn_to_index(gfn, slot->base_gfn, level);
return &slot->arch.rmap[level - PG_LEVEL_4K][idx];
}
static void rmap_remove(struct kvm *kvm, u64 *spte)
{
struct kvm_memslots *slots;
struct kvm_memory_slot *slot;
struct kvm_mmu_page *sp;
gfn_t gfn;
struct kvm_rmap_head *rmap_head;
sp = sptep_to_sp(spte);
gfn = kvm_mmu_page_get_gfn(sp, spte_index(spte));
/*
* Unlike rmap_add, rmap_remove does not run in the context of a vCPU
* so we have to determine which memslots to use based on context
* information in sp->role.
*/
slots = kvm_memslots_for_spte_role(kvm, sp->role);
slot = __gfn_to_memslot(slots, gfn);
rmap_head = gfn_to_rmap(gfn, sp->role.level, slot);
pte_list_remove(kvm, spte, rmap_head);
}
/*
* Used by the following functions to iterate through the sptes linked by a
* rmap. All fields are private and not assumed to be used outside.
*/
struct rmap_iterator {
/* private fields */
struct pte_list_desc *desc; /* holds the sptep if not NULL */
int pos; /* index of the sptep */
};
/*
* Iteration must be started by this function. This should also be used after
* removing/dropping sptes from the rmap link because in such cases the
* information in the iterator may not be valid.
*
* Returns sptep if found, NULL otherwise.
*/
static u64 *rmap_get_first(struct kvm_rmap_head *rmap_head,
struct rmap_iterator *iter)
{
u64 *sptep;
if (!rmap_head->val)
return NULL;
if (!(rmap_head->val & KVM_RMAP_MANY)) {
iter->desc = NULL;
sptep = (u64 *)rmap_head->val;
goto out;
}
iter->desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY);
iter->pos = 0;
sptep = iter->desc->sptes[iter->pos];
out:
BUG_ON(!is_shadow_present_pte(*sptep));
return sptep;
}
/*
* Must be used with a valid iterator: e.g. after rmap_get_first().
*
* Returns sptep if found, NULL otherwise.
*/
static u64 *rmap_get_next(struct rmap_iterator *iter)
{
u64 *sptep;
if (iter->desc) {
if (iter->pos < PTE_LIST_EXT - 1) {
++iter->pos;
sptep = iter->desc->sptes[iter->pos];
if (sptep)
goto out;
}
iter->desc = iter->desc->more;
if (iter->desc) {
iter->pos = 0;
/* desc->sptes[0] cannot be NULL */
sptep = iter->desc->sptes[iter->pos];
goto out;
}
}
return NULL;
out:
BUG_ON(!is_shadow_present_pte(*sptep));
return sptep;
}
#define for_each_rmap_spte(_rmap_head_, _iter_, _spte_) \
for (_spte_ = rmap_get_first(_rmap_head_, _iter_); \
_spte_; _spte_ = rmap_get_next(_iter_))
static void drop_spte(struct kvm *kvm, u64 *sptep)
{
u64 old_spte = mmu_spte_clear_track_bits(kvm, sptep);
if (is_shadow_present_pte(old_spte))
rmap_remove(kvm, sptep);
}
static void drop_large_spte(struct kvm *kvm, u64 *sptep, bool flush)
{
struct kvm_mmu_page *sp;
sp = sptep_to_sp(sptep);
WARN_ON_ONCE(sp->role.level == PG_LEVEL_4K);
drop_spte(kvm, sptep);
if (flush)
kvm_flush_remote_tlbs_sptep(kvm, sptep);
}
/*
* Write-protect on the specified @sptep, @pt_protect indicates whether
* spte write-protection is caused by protecting shadow page table.
*
* Note: write protection is difference between dirty logging and spte
* protection:
* - for dirty logging, the spte can be set to writable at anytime if
* its dirty bitmap is properly set.
* - for spte protection, the spte can be writable only after unsync-ing
* shadow page.
*
* Return true if tlb need be flushed.
*/
static bool spte_write_protect(u64 *sptep, bool pt_protect)
{
u64 spte = *sptep;
if (!is_writable_pte(spte) &&
!(pt_protect && is_mmu_writable_spte(spte)))
return false;
if (pt_protect)
spte &= ~shadow_mmu_writable_mask;
spte = spte & ~PT_WRITABLE_MASK;
return mmu_spte_update(sptep, spte);
}
static bool rmap_write_protect(struct kvm_rmap_head *rmap_head,
bool pt_protect)
{
u64 *sptep;
struct rmap_iterator iter;
bool flush = false;
for_each_rmap_spte(rmap_head, &iter, sptep)
flush |= spte_write_protect(sptep, pt_protect);
return flush;
}
static bool spte_clear_dirty(u64 *sptep)
{
u64 spte = *sptep;
KVM_MMU_WARN_ON(!spte_ad_enabled(spte));
spte &= ~shadow_dirty_mask;
return mmu_spte_update(sptep, spte);
}
static bool spte_wrprot_for_clear_dirty(u64 *sptep)
{
bool was_writable = test_and_clear_bit(PT_WRITABLE_SHIFT,
(unsigned long *)sptep);
if (was_writable && !spte_ad_enabled(*sptep))
kvm_set_pfn_dirty(spte_to_pfn(*sptep));
return was_writable;
}
/*
* Gets the GFN ready for another round of dirty logging by clearing the
* - D bit on ad-enabled SPTEs, and
* - W bit on ad-disabled SPTEs.
* Returns true iff any D or W bits were cleared.
*/
static bool __rmap_clear_dirty(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
const struct kvm_memory_slot *slot)
{
u64 *sptep;
struct rmap_iterator iter;
bool flush = false;
for_each_rmap_spte(rmap_head, &iter, sptep)
if (spte_ad_need_write_protect(*sptep))
flush |= spte_wrprot_for_clear_dirty(sptep);
else
flush |= spte_clear_dirty(sptep);
return flush;
}
static void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
struct kvm_memory_slot *slot,
gfn_t gfn_offset, unsigned long mask)
{
struct kvm_rmap_head *rmap_head;
if (tdp_mmu_enabled)
kvm_tdp_mmu_clear_dirty_pt_masked(kvm, slot,
slot->base_gfn + gfn_offset, mask, true);
if (!kvm_memslots_have_rmaps(kvm))
return;
while (mask) {
rmap_head = gfn_to_rmap(slot->base_gfn + gfn_offset + __ffs(mask),
PG_LEVEL_4K, slot);
rmap_write_protect(rmap_head, false);
/* clear the first set bit */
mask &= mask - 1;
}
}
static void kvm_mmu_clear_dirty_pt_masked(struct kvm *kvm,
struct kvm_memory_slot *slot,
gfn_t gfn_offset, unsigned long mask)
{
struct kvm_rmap_head *rmap_head;
if (tdp_mmu_enabled)
kvm_tdp_mmu_clear_dirty_pt_masked(kvm, slot,
slot->base_gfn + gfn_offset, mask, false);
if (!kvm_memslots_have_rmaps(kvm))
return;
while (mask) {
rmap_head = gfn_to_rmap(slot->base_gfn + gfn_offset + __ffs(mask),
PG_LEVEL_4K, slot);
__rmap_clear_dirty(kvm, rmap_head, slot);
/* clear the first set bit */
mask &= mask - 1;
}
}
void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
struct kvm_memory_slot *slot,
gfn_t gfn_offset, unsigned long mask)
{
/*
* If the slot was assumed to be "initially all dirty", write-protect
* huge pages to ensure they are split to 4KiB on the first write (KVM
* dirty logs at 4KiB granularity). If eager page splitting is enabled,
* immediately try to split huge pages, e.g. so that vCPUs don't get
* saddled with the cost of splitting.
*
* The gfn_offset is guaranteed to be aligned to 64, but the base_gfn
* of memslot has no such restriction, so the range can cross two large
* pages.
*/
if (kvm_dirty_log_manual_protect_and_init_set(kvm)) {
gfn_t start = slot->base_gfn + gfn_offset + __ffs(mask);
gfn_t end = slot->base_gfn + gfn_offset + __fls(mask);
if (READ_ONCE(eager_page_split))
kvm_mmu_try_split_huge_pages(kvm, slot, start, end + 1, PG_LEVEL_4K);
kvm_mmu_slot_gfn_write_protect(kvm, slot, start, PG_LEVEL_2M);
/* Cross two large pages? */
if (ALIGN(start << PAGE_SHIFT, PMD_SIZE) !=
ALIGN(end << PAGE_SHIFT, PMD_SIZE))
kvm_mmu_slot_gfn_write_protect(kvm, slot, end,
PG_LEVEL_2M);
}
/*
* (Re)Enable dirty logging for all 4KiB SPTEs that map the GFNs in
* mask. If PML is enabled and the GFN doesn't need to be write-
* protected for other reasons, e.g. shadow paging, clear the Dirty bit.
* Otherwise clear the Writable bit.
*
* Note that kvm_mmu_clear_dirty_pt_masked() is called whenever PML is
* enabled but it chooses between clearing the Dirty bit and Writeable
* bit based on the context.
*/
if (kvm_x86_ops.cpu_dirty_log_size)
kvm_mmu_clear_dirty_pt_masked(kvm, slot, gfn_offset, mask);
else
kvm_mmu_write_protect_pt_masked(kvm, slot, gfn_offset, mask);
}
int kvm_cpu_dirty_log_size(void)
{
return kvm_x86_ops.cpu_dirty_log_size;
}
bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm,
struct kvm_memory_slot *slot, u64 gfn,
int min_level)
{
struct kvm_rmap_head *rmap_head;
int i;
bool write_protected = false;
if (kvm_memslots_have_rmaps(kvm)) {
for (i = min_level; i <= KVM_MAX_HUGEPAGE_LEVEL; ++i) {
rmap_head = gfn_to_rmap(gfn, i, slot);
write_protected |= rmap_write_protect(rmap_head, true);
}
}
if (tdp_mmu_enabled)
write_protected |=
kvm_tdp_mmu_write_protect_gfn(kvm, slot, gfn, min_level);
return write_protected;
}
static bool kvm_vcpu_write_protect_gfn(struct kvm_vcpu *vcpu, u64 gfn)
{
struct kvm_memory_slot *slot;
slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
return kvm_mmu_slot_gfn_write_protect(vcpu->kvm, slot, gfn, PG_LEVEL_4K);
}
static bool kvm_zap_rmap(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
const struct kvm_memory_slot *slot)
{
return kvm_zap_all_rmap_sptes(kvm, rmap_head);
}
struct slot_rmap_walk_iterator {
/* input fields. */
const struct kvm_memory_slot *slot;
gfn_t start_gfn;
gfn_t end_gfn;
int start_level;
int end_level;
/* output fields. */
gfn_t gfn;
struct kvm_rmap_head *rmap;
int level;
/* private field. */
struct kvm_rmap_head *end_rmap;
};
static void rmap_walk_init_level(struct slot_rmap_walk_iterator *iterator,
int level)
{
iterator->level = level;
iterator->gfn = iterator->start_gfn;
iterator->rmap = gfn_to_rmap(iterator->gfn, level, iterator->slot);
iterator->end_rmap = gfn_to_rmap(iterator->end_gfn, level, iterator->slot);
}
static void slot_rmap_walk_init(struct slot_rmap_walk_iterator *iterator,
const struct kvm_memory_slot *slot,
int start_level, int end_level,
gfn_t start_gfn, gfn_t end_gfn)
{
iterator->slot = slot;
iterator->start_level = start_level;
iterator->end_level = end_level;
iterator->start_gfn = start_gfn;
iterator->end_gfn = end_gfn;
rmap_walk_init_level(iterator, iterator->start_level);
}
static bool slot_rmap_walk_okay(struct slot_rmap_walk_iterator *iterator)
{
return !!iterator->rmap;
}
static void slot_rmap_walk_next(struct slot_rmap_walk_iterator *iterator)
{
while (++iterator->rmap <= iterator->end_rmap) {
iterator->gfn += KVM_PAGES_PER_HPAGE(iterator->level);
if (iterator->rmap->val)
return;
}
if (++iterator->level > iterator->end_level) {
iterator->rmap = NULL;
return;
}
rmap_walk_init_level(iterator, iterator->level);
}
#define for_each_slot_rmap_range(_slot_, _start_level_, _end_level_, \
_start_gfn, _end_gfn, _iter_) \
for (slot_rmap_walk_init(_iter_, _slot_, _start_level_, \
_end_level_, _start_gfn, _end_gfn); \
slot_rmap_walk_okay(_iter_); \
slot_rmap_walk_next(_iter_))
/* The return value indicates if tlb flush on all vcpus is needed. */
typedef bool (*slot_rmaps_handler) (struct kvm *kvm,
struct kvm_rmap_head *rmap_head,
const struct kvm_memory_slot *slot);
static __always_inline bool __walk_slot_rmaps(struct kvm *kvm,
const struct kvm_memory_slot *slot,
slot_rmaps_handler fn,
int start_level, int end_level,
gfn_t start_gfn, gfn_t end_gfn,
bool can_yield, bool flush_on_yield,
bool flush)
{
struct slot_rmap_walk_iterator iterator;
lockdep_assert_held_write(&kvm->mmu_lock);
for_each_slot_rmap_range(slot, start_level, end_level, start_gfn,
end_gfn, &iterator) {
if (iterator.rmap)
flush |= fn(kvm, iterator.rmap, slot);
if (!can_yield)
continue;
if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) {
if (flush && flush_on_yield) {
kvm_flush_remote_tlbs_range(kvm, start_gfn,
iterator.gfn - start_gfn + 1);
flush = false;
}
cond_resched_rwlock_write(&kvm->mmu_lock);
}
}
return flush;
}
static __always_inline bool walk_slot_rmaps(struct kvm *kvm,
const struct kvm_memory_slot *slot,
slot_rmaps_handler fn,
int start_level, int end_level,
bool flush_on_yield)
{
return __walk_slot_rmaps(kvm, slot, fn, start_level, end_level,
slot->base_gfn, slot->base_gfn + slot->npages - 1,
true, flush_on_yield, false);
}
static __always_inline bool walk_slot_rmaps_4k(struct kvm *kvm,
const struct kvm_memory_slot *slot,
slot_rmaps_handler fn,
bool flush_on_yield)
{
return walk_slot_rmaps(kvm, slot, fn, PG_LEVEL_4K, PG_LEVEL_4K, flush_on_yield);
}
static bool __kvm_rmap_zap_gfn_range(struct kvm *kvm,
const struct kvm_memory_slot *slot,
gfn_t start, gfn_t end, bool can_yield,
bool flush)
{
return __walk_slot_rmaps(kvm, slot, kvm_zap_rmap,
PG_LEVEL_4K, KVM_MAX_HUGEPAGE_LEVEL,
start, end - 1, can_yield, true, flush);
}
bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
{
bool flush = false;
if (kvm_memslots_have_rmaps(kvm))
flush = __kvm_rmap_zap_gfn_range(kvm, range->slot,
range->start, range->end,
range->may_block, flush);
if (tdp_mmu_enabled)
flush = kvm_tdp_mmu_unmap_gfn_range(kvm, range, flush);
if (kvm_x86_ops.set_apic_access_page_addr &&
range->slot->id == APIC_ACCESS_PAGE_PRIVATE_MEMSLOT)
kvm_make_all_cpus_request(kvm, KVM_REQ_APIC_PAGE_RELOAD);
return flush;
}
#define RMAP_RECYCLE_THRESHOLD 1000
static void __rmap_add(struct kvm *kvm,
struct kvm_mmu_memory_cache *cache,
const struct kvm_memory_slot *slot,
u64 *spte, gfn_t gfn, unsigned int access)
{
struct kvm_mmu_page *sp;
struct kvm_rmap_head *rmap_head;
int rmap_count;
sp = sptep_to_sp(spte);
kvm_mmu_page_set_translation(sp, spte_index(spte), gfn, access);
kvm_update_page_stats(kvm, sp->role.level, 1);
rmap_head = gfn_to_rmap(gfn, sp->role.level, slot);
rmap_count = pte_list_add(cache, spte, rmap_head);
if (rmap_count > kvm->stat.max_mmu_rmap_size)
kvm->stat.max_mmu_rmap_size = rmap_count;
if (rmap_count > RMAP_RECYCLE_THRESHOLD) {
kvm_zap_all_rmap_sptes(kvm, rmap_head);
kvm_flush_remote_tlbs_gfn(kvm, gfn, sp->role.level);
}
}
static void rmap_add(struct kvm_vcpu *vcpu, const struct kvm_memory_slot *slot,
u64 *spte, gfn_t gfn, unsigned int access)
{
struct kvm_mmu_memory_cache *cache = &vcpu->arch.mmu_pte_list_desc_cache;
__rmap_add(vcpu->kvm, cache, slot, spte, gfn, access);
}
static bool kvm_rmap_age_gfn_range(struct kvm *kvm,
struct kvm_gfn_range *range, bool test_only)
{
struct slot_rmap_walk_iterator iterator;
struct rmap_iterator iter;
bool young = false;
u64 *sptep;
for_each_slot_rmap_range(range->slot, PG_LEVEL_4K, KVM_MAX_HUGEPAGE_LEVEL,
range->start, range->end - 1, &iterator) {
for_each_rmap_spte(iterator.rmap, &iter, sptep) {
u64 spte = *sptep;
if (!is_accessed_spte(spte))
continue;
if (test_only)
return true;
if (spte_ad_enabled(spte)) {
clear_bit((ffs(shadow_accessed_mask) - 1),
(unsigned long *)sptep);
} else {
/*
* Capture the dirty status of the page, so that
* it doesn't get lost when the SPTE is marked
* for access tracking.
*/
if (is_writable_pte(spte))
kvm_set_pfn_dirty(spte_to_pfn(spte));
spte = mark_spte_for_access_track(spte);
mmu_spte_update_no_track(sptep, spte);
}
young = true;
}
}
return young;
}
bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
{
bool young = false;
if (kvm_memslots_have_rmaps(kvm))
young = kvm_rmap_age_gfn_range(kvm, range, false);
if (tdp_mmu_enabled)
young |= kvm_tdp_mmu_age_gfn_range(kvm, range);
return young;
}
bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
{
bool young = false;
if (kvm_memslots_have_rmaps(kvm))
young = kvm_rmap_age_gfn_range(kvm, range, true);
if (tdp_mmu_enabled)
young |= kvm_tdp_mmu_test_age_gfn(kvm, range);
return young;
}
static void kvm_mmu_check_sptes_at_free(struct kvm_mmu_page *sp)
{
#ifdef CONFIG_KVM_PROVE_MMU
int i;
for (i = 0; i < SPTE_ENT_PER_PAGE; i++) {
if (KVM_MMU_WARN_ON(is_shadow_present_pte(sp->spt[i])))
pr_err_ratelimited("SPTE %llx (@ %p) for gfn %llx shadow-present at free",
sp->spt[i], &sp->spt[i],
kvm_mmu_page_get_gfn(sp, i));
}
#endif
}
/*
* This value is the sum of all of the kvm instances's
* kvm->arch.n_used_mmu_pages values. We need a global,
* aggregate version in order to make the slab shrinker
* faster
*/
static inline void kvm_mod_used_mmu_pages(struct kvm *kvm, long nr)
{
kvm->arch.n_used_mmu_pages += nr;
percpu_counter_add(&kvm_total_used_mmu_pages, nr);
}
static void kvm_account_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
kvm_mod_used_mmu_pages(kvm, +1);
kvm_account_pgtable_pages((void *)sp->spt, +1);
}
static void kvm_unaccount_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
kvm_mod_used_mmu_pages(kvm, -1);
kvm_account_pgtable_pages((void *)sp->spt, -1);
}
static void kvm_mmu_free_shadow_page(struct kvm_mmu_page *sp)
{
kvm_mmu_check_sptes_at_free(sp);
hlist_del(&sp->hash_link);
list_del(&sp->link);
free_page((unsigned long)sp->spt);
free_page((unsigned long)sp->shadowed_translation);
kmem_cache_free(mmu_page_header_cache, sp);
}
static unsigned kvm_page_table_hashfn(gfn_t gfn)
{
return hash_64(gfn, KVM_MMU_HASH_SHIFT);
}
static void mmu_page_add_parent_pte(struct kvm_mmu_memory_cache *cache,
struct kvm_mmu_page *sp, u64 *parent_pte)
{
if (!parent_pte)
return;
pte_list_add(cache, parent_pte, &sp->parent_ptes);
}
static void mmu_page_remove_parent_pte(struct kvm *kvm, struct kvm_mmu_page *sp,
u64 *parent_pte)
{
pte_list_remove(kvm, parent_pte, &sp->parent_ptes);
}
static void drop_parent_pte(struct kvm *kvm, struct kvm_mmu_page *sp,
u64 *parent_pte)
{
mmu_page_remove_parent_pte(kvm, sp, parent_pte);
mmu_spte_clear_no_track(parent_pte);
}
static void mark_unsync(u64 *spte);
static void kvm_mmu_mark_parents_unsync(struct kvm_mmu_page *sp)
{
u64 *sptep;
struct rmap_iterator iter;
for_each_rmap_spte(&sp->parent_ptes, &iter, sptep) {
mark_unsync(sptep);
}
}
static void mark_unsync(u64 *spte)
{
struct kvm_mmu_page *sp;
sp = sptep_to_sp(spte);
if (__test_and_set_bit(spte_index(spte), sp->unsync_child_bitmap))
return;
if (sp->unsync_children++)
return;
kvm_mmu_mark_parents_unsync(sp);
}
#define KVM_PAGE_ARRAY_NR 16
struct kvm_mmu_pages {
struct mmu_page_and_offset {
struct kvm_mmu_page *sp;
unsigned int idx;
} page[KVM_PAGE_ARRAY_NR];
unsigned int nr;
};
static int mmu_pages_add(struct kvm_mmu_pages *pvec, struct kvm_mmu_page *sp,
int idx)
{
int i;
if (sp->unsync)
for (i=0; i < pvec->nr; i++)
if (pvec->page[i].sp == sp)
return 0;
pvec->page[pvec->nr].sp = sp;
pvec->page[pvec->nr].idx = idx;
pvec->nr++;
return (pvec->nr == KVM_PAGE_ARRAY_NR);
}
static inline void clear_unsync_child_bit(struct kvm_mmu_page *sp, int idx)
{
--sp->unsync_children;
WARN_ON_ONCE((int)sp->unsync_children < 0);
__clear_bit(idx, sp->unsync_child_bitmap);
}
static int __mmu_unsync_walk(struct kvm_mmu_page *sp,
struct kvm_mmu_pages *pvec)
{
int i, ret, nr_unsync_leaf = 0;
for_each_set_bit(i, sp->unsync_child_bitmap, 512) {
struct kvm_mmu_page *child;
u64 ent = sp->spt[i];
if (!is_shadow_present_pte(ent) || is_large_pte(ent)) {
clear_unsync_child_bit(sp, i);
continue;
}
child = spte_to_child_sp(ent);
if (child->unsync_children) {
if (mmu_pages_add(pvec, child, i))
return -ENOSPC;
ret = __mmu_unsync_walk(child, pvec);
if (!ret) {
clear_unsync_child_bit(sp, i);
continue;
} else if (ret > 0) {
nr_unsync_leaf += ret;
} else
return ret;
} else if (child->unsync) {
nr_unsync_leaf++;
if (mmu_pages_add(pvec, child, i))
return -ENOSPC;
} else
clear_unsync_child_bit(sp, i);
}
return nr_unsync_leaf;
}
#define INVALID_INDEX (-1)
static int mmu_unsync_walk(struct kvm_mmu_page *sp,
struct kvm_mmu_pages *pvec)
{
pvec->nr = 0;
if (!sp->unsync_children)
return 0;
mmu_pages_add(pvec, sp, INVALID_INDEX);
return __mmu_unsync_walk(sp, pvec);
}
static void kvm_unlink_unsync_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
WARN_ON_ONCE(!sp->unsync);
trace_kvm_mmu_sync_page(sp);
sp->unsync = 0;
--kvm->stat.mmu_unsync;
}
static bool kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp,
struct list_head *invalid_list);
static void kvm_mmu_commit_zap_page(struct kvm *kvm,
struct list_head *invalid_list);
static bool sp_has_gptes(struct kvm_mmu_page *sp)
{
if (sp->role.direct)
return false;
if (sp->role.passthrough)
return false;
return true;
}
#define for_each_valid_sp(_kvm, _sp, _list) \
hlist_for_each_entry(_sp, _list, hash_link) \
if (is_obsolete_sp((_kvm), (_sp))) { \
} else
#define for_each_gfn_valid_sp(_kvm, _sp, _gfn) \
for_each_valid_sp(_kvm, _sp, \
&(_kvm)->arch.mmu_page_hash[kvm_page_table_hashfn(_gfn)]) \
if ((_sp)->gfn != (_gfn)) {} else
#define for_each_gfn_valid_sp_with_gptes(_kvm, _sp, _gfn) \
for_each_gfn_valid_sp(_kvm, _sp, _gfn) \
if (!sp_has_gptes(_sp)) {} else
static bool kvm_sync_page_check(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
{
union kvm_mmu_page_role root_role = vcpu->arch.mmu->root_role;
/*
* Ignore various flags when verifying that it's safe to sync a shadow
* page using the current MMU context.
*
* - level: not part of the overall MMU role and will never match as the MMU's
* level tracks the root level
* - access: updated based on the new guest PTE
* - quadrant: not part of the overall MMU role (similar to level)
*/
const union kvm_mmu_page_role sync_role_ign = {
.level = 0xf,
.access = 0x7,
.quadrant = 0x3,
.passthrough = 0x1,
};
/*
* Direct pages can never be unsync, and KVM should never attempt to
* sync a shadow page for a different MMU context, e.g. if the role
* differs then the memslot lookup (SMM vs. non-SMM) will be bogus, the
* reserved bits checks will be wrong, etc...
*/
if (WARN_ON_ONCE(sp->role.direct || !vcpu->arch.mmu->sync_spte ||
(sp->role.word ^ root_role.word) & ~sync_role_ign.word))
return false;
return true;
}
static int kvm_sync_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, int i)
{
/* sp->spt[i] has initial value of shadow page table allocation */
if (sp->spt[i] == SHADOW_NONPRESENT_VALUE)
return 0;
return vcpu->arch.mmu->sync_spte(vcpu, sp, i);
}
static int __kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
{
int flush = 0;
int i;
if (!kvm_sync_page_check(vcpu, sp))
return -1;
for (i = 0; i < SPTE_ENT_PER_PAGE; i++) {
int ret = kvm_sync_spte(vcpu, sp, i);
if (ret < -1)
return -1;
flush |= ret;
}
/*
* Note, any flush is purely for KVM's correctness, e.g. when dropping
* an existing SPTE or clearing W/A/D bits to ensure an mmu_notifier
* unmap or dirty logging event doesn't fail to flush. The guest is
* responsible for flushing the TLB to ensure any changes in protection
* bits are recognized, i.e. until the guest flushes or page faults on
* a relevant address, KVM is architecturally allowed to let vCPUs use
* cached translations with the old protection bits.
*/
return flush;
}
static int kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
struct list_head *invalid_list)
{
int ret = __kvm_sync_page(vcpu, sp);
if (ret < 0)
kvm_mmu_prepare_zap_page(vcpu->kvm, sp, invalid_list);
return ret;
}
static bool kvm_mmu_remote_flush_or_zap(struct kvm *kvm,
struct list_head *invalid_list,
bool remote_flush)
{
if (!remote_flush && list_empty(invalid_list))
return false;
if (!list_empty(invalid_list))
kvm_mmu_commit_zap_page(kvm, invalid_list);
else
kvm_flush_remote_tlbs(kvm);
return true;
}
static bool is_obsolete_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
{
if (sp->role.invalid)
return true;
/* TDP MMU pages do not use the MMU generation. */
return !is_tdp_mmu_page(sp) &&
unlikely(sp->mmu_valid_gen != kvm->arch.mmu_valid_gen);
}
struct mmu_page_path {
struct kvm_mmu_page *parent[PT64_ROOT_MAX_LEVEL];
unsigned int idx[PT64_ROOT_MAX_LEVEL];
};
#define for_each_sp(pvec, sp, parents, i) \
for (i = mmu_pages_first(&pvec, &parents); \
i < pvec.nr && ({ sp = pvec.page[i].sp; 1;}); \
i = mmu_pages_next(&pvec, &parents, i))
static int mmu_pages_next(struct kvm_mmu_pages *pvec,
struct mmu_page_path *parents,
int i)
{
int n;
for (n = i+1; n < pvec->nr; n++) {
struct kvm_mmu_page *sp = pvec->page[n].sp;
unsigned idx = pvec->page[n].idx;
int level = sp->role.level;
parents->idx[level-1] = idx;
if (level == PG_LEVEL_4K)
break;
parents->parent[level-2] = sp;
}
return n;
}
static int mmu_pages_first(struct kvm_mmu_pages *pvec,
struct mmu_page_path *parents)
{
struct kvm_mmu_page *sp;
int level;
if (pvec->nr == 0)
return 0;
WARN_ON_ONCE(pvec->page[0].idx != INVALID_INDEX);
sp = pvec->page[0].sp;
level = sp->role.level;
WARN_ON_ONCE(level == PG_LEVEL_4K);
parents->parent[level-2] = sp;
/* Also set up a sentinel. Further entries in pvec are all
* children of sp, so this element is never overwritten.
*/
parents->parent[level-1] = NULL;
return mmu_pages_next(pvec, parents, 0);
}
static void mmu_pages_clear_parents(struct mmu_page_path *parents)
{
struct kvm_mmu_page *sp;
unsigned int level = 0;
do {
unsigned int idx = parents->idx[level];
sp = parents->parent[level];
if (!sp)
return;
WARN_ON_ONCE(idx == INVALID_INDEX);
clear_unsync_child_bit(sp, idx);
level++;
} while (!sp->unsync_children);
}
static int mmu_sync_children(struct kvm_vcpu *vcpu,
struct kvm_mmu_page *parent, bool can_yield)
{
int i;
struct kvm_mmu_page *sp;
struct mmu_page_path parents;
struct kvm_mmu_pages pages;
LIST_HEAD(invalid_list);
bool flush = false;
while (mmu_unsync_walk(parent, &pages)) {
bool protected = false;
for_each_sp(pages, sp, parents, i)
protected |= kvm_vcpu_write_protect_gfn(vcpu, sp->gfn);
if (protected) {
kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, true);
flush = false;
}
for_each_sp(pages, sp, parents, i) {
kvm_unlink_unsync_page(vcpu->kvm, sp);
flush |= kvm_sync_page(vcpu, sp, &invalid_list) > 0;
mmu_pages_clear_parents(&parents);
}
if (need_resched() || rwlock_needbreak(&vcpu->kvm->mmu_lock)) {
kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, flush);
if (!can_yield) {
kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);
return -EINTR;
}
cond_resched_rwlock_write(&vcpu->kvm->mmu_lock);
flush = false;
}
}
kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, flush);
return 0;
}
static void __clear_sp_write_flooding_count(struct kvm_mmu_page *sp)
{
atomic_set(&sp->write_flooding_count, 0);
}
static void clear_sp_write_flooding_count(u64 *spte)
{
__clear_sp_write_flooding_count(sptep_to_sp(spte));
}
/*
* The vCPU is required when finding indirect shadow pages; the shadow
* page may already exist and syncing it needs the vCPU pointer in
* order to read guest page tables. Direct shadow pages are never
* unsync, thus @vcpu can be NULL if @role.direct is true.
*/
static struct kvm_mmu_page *kvm_mmu_find_shadow_page(struct kvm *kvm,
struct kvm_vcpu *vcpu,
gfn_t gfn,
struct hlist_head *sp_list,
union kvm_mmu_page_role role)
{
struct kvm_mmu_page *sp;
int ret;
int collisions = 0;
LIST_HEAD(invalid_list);
for_each_valid_sp(kvm, sp, sp_list) {
if (sp->gfn != gfn) {
collisions++;
continue;
}
if (sp->role.word != role.word) {
/*
* If the guest is creating an upper-level page, zap
* unsync pages for the same gfn. While it's possible
* the guest is using recursive page tables, in all
* likelihood the guest has stopped using the unsync
* page and is installing a completely unrelated page.
* Unsync pages must not be left as is, because the new
* upper-level page will be write-protected.
*/
if (role.level > PG_LEVEL_4K && sp->unsync)
kvm_mmu_prepare_zap_page(kvm, sp,
&invalid_list);
continue;
}
/* unsync and write-flooding only apply to indirect SPs. */
if (sp->role.direct)
goto out;
if (sp->unsync) {
if (KVM_BUG_ON(!vcpu, kvm))
break;
/*
* The page is good, but is stale. kvm_sync_page does
* get the latest guest state, but (unlike mmu_unsync_children)
* it doesn't write-protect the page or mark it synchronized!
* This way the validity of the mapping is ensured, but the
* overhead of write protection is not incurred until the
* guest invalidates the TLB mapping. This allows multiple
* SPs for a single gfn to be unsync.
*
* If the sync fails, the page is zapped. If so, break
* in order to rebuild it.
*/
ret = kvm_sync_page(vcpu, sp, &invalid_list);
if (ret < 0)
break;
WARN_ON_ONCE(!list_empty(&invalid_list));
if (ret > 0)
kvm_flush_remote_tlbs(kvm);
}
__clear_sp_write_flooding_count(sp);
goto out;
}
sp = NULL;
++kvm->stat.mmu_cache_miss;
out:
kvm_mmu_commit_zap_page(kvm, &invalid_list);
if (collisions > kvm->stat.max_mmu_page_hash_collisions)
kvm->stat.max_mmu_page_hash_collisions = collisions;
return sp;
}
/* Caches used when allocating a new shadow page. */
struct shadow_page_caches {
struct kvm_mmu_memory_cache *page_header_cache;
struct kvm_mmu_memory_cache *shadow_page_cache;
struct kvm_mmu_memory_cache *shadowed_info_cache;
};
static struct kvm_mmu_page *kvm_mmu_alloc_shadow_page(struct kvm *kvm,
struct shadow_page_caches *caches,
gfn_t gfn,
struct hlist_head *sp_list,
union kvm_mmu_page_role role)
{
struct kvm_mmu_page *sp;
sp = kvm_mmu_memory_cache_alloc(caches->page_header_cache);
sp->spt = kvm_mmu_memory_cache_alloc(caches->shadow_page_cache);
if (!role.direct && role.level <= KVM_MAX_HUGEPAGE_LEVEL)
sp->shadowed_translation = kvm_mmu_memory_cache_alloc(caches->shadowed_info_cache);
set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
INIT_LIST_HEAD(&sp->possible_nx_huge_page_link);
/*
* active_mmu_pages must be a FIFO list, as kvm_zap_obsolete_pages()
* depends on valid pages being added to the head of the list. See
* comments in kvm_zap_obsolete_pages().
*/
sp->mmu_valid_gen = kvm->arch.mmu_valid_gen;
list_add(&sp->link, &kvm->arch.active_mmu_pages);
kvm_account_mmu_page(kvm, sp);
sp->gfn = gfn;
sp->role = role;
hlist_add_head(&sp->hash_link, sp_list);
if (sp_has_gptes(sp))
account_shadowed(kvm, sp);
return sp;
}
/* Note, @vcpu may be NULL if @role.direct is true; see kvm_mmu_find_shadow_page. */
static struct kvm_mmu_page *__kvm_mmu_get_shadow_page(struct kvm *kvm,
struct kvm_vcpu *vcpu,
struct shadow_page_caches *caches,
gfn_t gfn,
union kvm_mmu_page_role role)
{
struct hlist_head *sp_list;
struct kvm_mmu_page *sp;
bool created = false;
sp_list = &kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)];
sp = kvm_mmu_find_shadow_page(kvm, vcpu, gfn, sp_list, role);
if (!sp) {
created = true;
sp = kvm_mmu_alloc_shadow_page(kvm, caches, gfn, sp_list, role);
}
trace_kvm_mmu_get_page(sp, created);
return sp;
}
static struct kvm_mmu_page *kvm_mmu_get_shadow_page(struct kvm_vcpu *vcpu,
gfn_t gfn,
union kvm_mmu_page_role role)
{
struct shadow_page_caches caches = {
.page_header_cache = &vcpu->arch.mmu_page_header_cache,
.shadow_page_cache = &vcpu->arch.mmu_shadow_page_cache,
.shadowed_info_cache = &vcpu->arch.mmu_shadowed_info_cache,
};
return __kvm_mmu_get_shadow_page(vcpu->kvm, vcpu, &caches, gfn, role);
}
static union kvm_mmu_page_role kvm_mmu_child_role(u64 *sptep, bool direct,
unsigned int access)
{
struct kvm_mmu_page *parent_sp = sptep_to_sp(sptep);
union kvm_mmu_page_role role;
role = parent_sp->role;
role.level--;
role.access = access;
role.direct = direct;
role.passthrough = 0;
/*
* If the guest has 4-byte PTEs then that means it's using 32-bit,
* 2-level, non-PAE paging. KVM shadows such guests with PAE paging
* (i.e. 8-byte PTEs). The difference in PTE size means that KVM must
* shadow each guest page table with multiple shadow page tables, which
* requires extra bookkeeping in the role.
*
* Specifically, to shadow the guest's page directory (which covers a
* 4GiB address space), KVM uses 4 PAE page directories, each mapping
* 1GiB of the address space. @role.quadrant encodes which quarter of
* the address space each maps.
*
* To shadow the guest's page tables (which each map a 4MiB region), KVM
* uses 2 PAE page tables, each mapping a 2MiB region. For these,
* @role.quadrant encodes which half of the region they map.
*
* Concretely, a 4-byte PDE consumes bits 31:22, while an 8-byte PDE
* consumes bits 29:21. To consume bits 31:30, KVM's uses 4 shadow
* PDPTEs; those 4 PAE page directories are pre-allocated and their
* quadrant is assigned in mmu_alloc_root(). A 4-byte PTE consumes
* bits 21:12, while an 8-byte PTE consumes bits 20:12. To consume
* bit 21 in the PTE (the child here), KVM propagates that bit to the
* quadrant, i.e. sets quadrant to '0' or '1'. The parent 8-byte PDE
* covers bit 21 (see above), thus the quadrant is calculated from the
* _least_ significant bit of the PDE index.
*/
if (role.has_4_byte_gpte) {
WARN_ON_ONCE(role.level != PG_LEVEL_4K);
role.quadrant = spte_index(sptep) & 1;
}
return role;
}
static struct kvm_mmu_page *kvm_mmu_get_child_sp(struct kvm_vcpu *vcpu,
u64 *sptep, gfn_t gfn,
bool direct, unsigned int access)
{
union kvm_mmu_page_role role;
if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep))
return ERR_PTR(-EEXIST);
role = kvm_mmu_child_role(sptep, direct, access);
return kvm_mmu_get_shadow_page(vcpu, gfn, role);
}
static void shadow_walk_init_using_root(struct kvm_shadow_walk_iterator *iterator,
struct kvm_vcpu *vcpu, hpa_t root,
u64 addr)
{
iterator->addr = addr;
iterator->shadow_addr = root;
iterator->level = vcpu->arch.mmu->root_role.level;
if (iterator->level >= PT64_ROOT_4LEVEL &&
vcpu->arch.mmu->cpu_role.base.level < PT64_ROOT_4LEVEL &&
!vcpu->arch.mmu->root_role.direct)
iterator->level = PT32E_ROOT_LEVEL;
if (iterator->level == PT32E_ROOT_LEVEL) {
/*
* prev_root is currently only used for 64-bit hosts. So only
* the active root_hpa is valid here.
*/
BUG_ON(root != vcpu->arch.mmu->root.hpa);
iterator->shadow_addr
= vcpu->arch.mmu->pae_root[(addr >> 30) & 3];
iterator->shadow_addr &= SPTE_BASE_ADDR_MASK;
--iterator->level;
if (!iterator->shadow_addr)
iterator->level = 0;
}
}
static void shadow_walk_init(struct kvm_shadow_walk_iterator *iterator,
struct kvm_vcpu *vcpu, u64 addr)
{
shadow_walk_init_using_root(iterator, vcpu, vcpu->arch.mmu->root.hpa,
addr);
}
static bool shadow_walk_okay(struct kvm_shadow_walk_iterator *iterator)
{
if (iterator->level < PG_LEVEL_4K)
return false;
iterator->index = SPTE_INDEX(iterator->addr, iterator->level);
iterator->sptep = ((u64 *)__va(iterator->shadow_addr)) + iterator->index;
return true;
}
static void __shadow_walk_next(struct kvm_shadow_walk_iterator *iterator,
u64 spte)
{
if (!is_shadow_present_pte(spte) || is_last_spte(spte, iterator->level)) {
iterator->level = 0;
return;
}
iterator->shadow_addr = spte & SPTE_BASE_ADDR_MASK;
--iterator->level;
}
static void shadow_walk_next(struct kvm_shadow_walk_iterator *iterator)
{
__shadow_walk_next(iterator, *iterator->sptep);
}
static void __link_shadow_page(struct kvm *kvm,
struct kvm_mmu_memory_cache *cache, u64 *sptep,
struct kvm_mmu_page *sp, bool flush)
{
u64 spte;
BUILD_BUG_ON(VMX_EPT_WRITABLE_MASK != PT_WRITABLE_MASK);
/*
* If an SPTE is present already, it must be a leaf and therefore
* a large one. Drop it, and flush the TLB if needed, before
* installing sp.
*/
if (is_shadow_present_pte(*sptep))
drop_large_spte(kvm, sptep, flush);
spte = make_nonleaf_spte(sp->spt, sp_ad_disabled(sp));
mmu_spte_set(sptep, spte);
mmu_page_add_parent_pte(cache, sp, sptep);
/*
* The non-direct sub-pagetable must be updated before linking. For
* L1 sp, the pagetable is updated via kvm_sync_page() in
* kvm_mmu_find_shadow_page() without write-protecting the gfn,
* so sp->unsync can be true or false. For higher level non-direct
* sp, the pagetable is updated/synced via mmu_sync_children() in
* FNAME(fetch)(), so sp->unsync_children can only be false.
* WARN_ON_ONCE() if anything happens unexpectedly.
*/
if (WARN_ON_ONCE(sp->unsync_children) || sp->unsync)
mark_unsync(sptep);
}
static void link_shadow_page(struct kvm_vcpu *vcpu, u64 *sptep,
struct kvm_mmu_page *sp)
{
__link_shadow_page(vcpu->kvm, &vcpu->arch.mmu_pte_list_desc_cache, sptep, sp, true);
}
static void validate_direct_spte(struct kvm_vcpu *vcpu, u64 *sptep,
unsigned direct_access)
{
if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)) {
struct kvm_mmu_page *child;
/*
* For the direct sp, if the guest pte's dirty bit
* changed form clean to dirty, it will corrupt the
* sp's access: allow writable in the read-only sp,
* so we should update the spte at this point to get
* a new sp with the correct access.
*/
child = spte_to_child_sp(*sptep);
if (child->role.access == direct_access)
return;
drop_parent_pte(vcpu->kvm, child, sptep);
kvm_flush_remote_tlbs_sptep(vcpu->kvm, sptep);
}
}
/* Returns the number of zapped non-leaf child shadow pages. */
static int mmu_page_zap_pte(struct kvm *kvm, struct kvm_mmu_page *sp,
u64 *spte, struct list_head *invalid_list)
{
u64 pte;
struct kvm_mmu_page *child;
pte = *spte;
if (is_shadow_present_pte(pte)) {
if (is_last_spte(pte, sp->role.level)) {
drop_spte(kvm, spte);
} else {
child = spte_to_child_sp(pte);
drop_parent_pte(kvm, child, spte);
/*
* Recursively zap nested TDP SPs, parentless SPs are
* unlikely to be used again in the near future. This
* avoids retaining a large number of stale nested SPs.
*/
if (tdp_enabled && invalid_list &&
child->role.guest_mode && !child->parent_ptes.val)
return kvm_mmu_prepare_zap_page(kvm, child,
invalid_list);
}
} else if (is_mmio_spte(kvm, pte)) {
mmu_spte_clear_no_track(spte);
}
return 0;
}
static int kvm_mmu_page_unlink_children(struct kvm *kvm,
struct kvm_mmu_page *sp,
struct list_head *invalid_list)
{
int zapped = 0;
unsigned i;
for (i = 0; i < SPTE_ENT_PER_PAGE; ++i)
zapped += mmu_page_zap_pte(kvm, sp, sp->spt + i, invalid_list);
return zapped;
}
static void kvm_mmu_unlink_parents(struct kvm *kvm, struct kvm_mmu_page *sp)
{
u64 *sptep;
struct rmap_iterator iter;
while ((sptep = rmap_get_first(&sp->parent_ptes, &iter)))
drop_parent_pte(kvm, sp, sptep);
}
static int mmu_zap_unsync_children(struct kvm *kvm,
struct kvm_mmu_page *parent,
struct list_head *invalid_list)
{
int i, zapped = 0;
struct mmu_page_path parents;
struct kvm_mmu_pages pages;
if (parent->role.level == PG_LEVEL_4K)
return 0;
while (mmu_unsync_walk(parent, &pages)) {
struct kvm_mmu_page *sp;
for_each_sp(pages, sp, parents, i) {
kvm_mmu_prepare_zap_page(kvm, sp, invalid_list);
mmu_pages_clear_parents(&parents);
zapped++;
}
}
return zapped;
}
static bool __kvm_mmu_prepare_zap_page(struct kvm *kvm,
struct kvm_mmu_page *sp,
struct list_head *invalid_list,
int *nr_zapped)
{
bool list_unstable, zapped_root = false;
lockdep_assert_held_write(&kvm->mmu_lock);
trace_kvm_mmu_prepare_zap_page(sp);
++kvm->stat.mmu_shadow_zapped;
*nr_zapped = mmu_zap_unsync_children(kvm, sp, invalid_list);
*nr_zapped += kvm_mmu_page_unlink_children(kvm, sp, invalid_list);
kvm_mmu_unlink_parents(kvm, sp);
/* Zapping children means active_mmu_pages has become unstable. */
list_unstable = *nr_zapped;
if (!sp->role.invalid && sp_has_gptes(sp))
unaccount_shadowed(kvm, sp);
if (sp->unsync)
kvm_unlink_unsync_page(kvm, sp);
if (!sp->root_count) {
/* Count self */
(*nr_zapped)++;
/*
* Already invalid pages (previously active roots) are not on
* the active page list. See list_del() in the "else" case of
* !sp->root_count.
*/
if (sp->role.invalid)
list_add(&sp->link, invalid_list);
else
list_move(&sp->link, invalid_list);
kvm_unaccount_mmu_page(kvm, sp);
} else {
/*
* Remove the active root from the active page list, the root
* will be explicitly freed when the root_count hits zero.
*/
list_del(&sp->link);
/*
* Obsolete pages cannot be used on any vCPUs, see the comment
* in kvm_mmu_zap_all_fast(). Note, is_obsolete_sp() also
* treats invalid shadow pages as being obsolete.
*/
zapped_root = !is_obsolete_sp(kvm, sp);
}
if (sp->nx_huge_page_disallowed)
unaccount_nx_huge_page(kvm, sp);
sp->role.invalid = 1;
/*
* Make the request to free obsolete roots after marking the root
* invalid, otherwise other vCPUs may not see it as invalid.
*/
if (zapped_root)
kvm_make_all_cpus_request(kvm, KVM_REQ_MMU_FREE_OBSOLETE_ROOTS);
return list_unstable;
}
static bool kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp,
struct list_head *invalid_list)
{
int nr_zapped;
__kvm_mmu_prepare_zap_page(kvm, sp, invalid_list, &nr_zapped);
return nr_zapped;
}
static void kvm_mmu_commit_zap_page(struct kvm *kvm,
struct list_head *invalid_list)
{
struct kvm_mmu_page *sp, *nsp;
if (list_empty(invalid_list))
return;
/*
* We need to make sure everyone sees our modifications to
* the page tables and see changes to vcpu->mode here. The barrier
* in the kvm_flush_remote_tlbs() achieves this. This pairs
* with vcpu_enter_guest and walk_shadow_page_lockless_begin/end.
*
* In addition, kvm_flush_remote_tlbs waits for all vcpus to exit
* guest mode and/or lockless shadow page table walks.
*/
kvm_flush_remote_tlbs(kvm);
list_for_each_entry_safe(sp, nsp, invalid_list, link) {
WARN_ON_ONCE(!sp->role.invalid || sp->root_count);
kvm_mmu_free_shadow_page(sp);
}
}
static unsigned long kvm_mmu_zap_oldest_mmu_pages(struct kvm *kvm,
unsigned long nr_to_zap)
{
unsigned long total_zapped = 0;
struct kvm_mmu_page *sp, *tmp;
LIST_HEAD(invalid_list);
bool unstable;
int nr_zapped;
if (list_empty(&kvm->arch.active_mmu_pages))
return 0;
restart:
list_for_each_entry_safe_reverse(sp, tmp, &kvm->arch.active_mmu_pages, link) {
/*
* Don't zap active root pages, the page itself can't be freed
* and zapping it will just force vCPUs to realloc and reload.
*/
if (sp->root_count)
continue;
unstable = __kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list,
&nr_zapped);
total_zapped += nr_zapped;
if (total_zapped >= nr_to_zap)
break;
if (unstable)
goto restart;
}
kvm_mmu_commit_zap_page(kvm, &invalid_list);
kvm->stat.mmu_recycled += total_zapped;
return total_zapped;
}
static inline unsigned long kvm_mmu_available_pages(struct kvm *kvm)
{
if (kvm->arch.n_max_mmu_pages > kvm->arch.n_used_mmu_pages)
return kvm->arch.n_max_mmu_pages -
kvm->arch.n_used_mmu_pages;
return 0;
}
static int make_mmu_pages_available(struct kvm_vcpu *vcpu)
{
unsigned long avail = kvm_mmu_available_pages(vcpu->kvm);
if (likely(avail >= KVM_MIN_FREE_MMU_PAGES))
return 0;
kvm_mmu_zap_oldest_mmu_pages(vcpu->kvm, KVM_REFILL_PAGES - avail);
/*
* Note, this check is intentionally soft, it only guarantees that one
* page is available, while the caller may end up allocating as many as
* four pages, e.g. for PAE roots or for 5-level paging. Temporarily
* exceeding the (arbitrary by default) limit will not harm the host,
* being too aggressive may unnecessarily kill the guest, and getting an
* exact count is far more trouble than it's worth, especially in the
* page fault paths.
*/
if (!kvm_mmu_available_pages(vcpu->kvm))
return -ENOSPC;
return 0;
}
/*
* Changing the number of mmu pages allocated to the vm
* Note: if goal_nr_mmu_pages is too small, you will get dead lock
*/
void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned long goal_nr_mmu_pages)
{
write_lock(&kvm->mmu_lock);
if (kvm->arch.n_used_mmu_pages > goal_nr_mmu_pages) {
kvm_mmu_zap_oldest_mmu_pages(kvm, kvm->arch.n_used_mmu_pages -
goal_nr_mmu_pages);
goal_nr_mmu_pages = kvm->arch.n_used_mmu_pages;
}
kvm->arch.n_max_mmu_pages = goal_nr_mmu_pages;
write_unlock(&kvm->mmu_lock);
}
bool __kvm_mmu_unprotect_gfn_and_retry(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
bool always_retry)
{
struct kvm *kvm = vcpu->kvm;
LIST_HEAD(invalid_list);
struct kvm_mmu_page *sp;
gpa_t gpa = cr2_or_gpa;
bool r = false;
/*
* Bail early if there aren't any write-protected shadow pages to avoid
* unnecessarily taking mmu_lock lock, e.g. if the gfn is write-tracked
* by a third party. Reading indirect_shadow_pages without holding
* mmu_lock is safe, as this is purely an optimization, i.e. a false
* positive is benign, and a false negative will simply result in KVM
* skipping the unprotect+retry path, which is also an optimization.
*/
if (!READ_ONCE(kvm->arch.indirect_shadow_pages))
goto out;
if (!vcpu->arch.mmu->root_role.direct) {
gpa = kvm_mmu_gva_to_gpa_write(vcpu, cr2_or_gpa, NULL);
if (gpa == INVALID_GPA)
goto out;
}
write_lock(&kvm->mmu_lock);
for_each_gfn_valid_sp_with_gptes(kvm, sp, gpa_to_gfn(gpa))
kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
/*
* Snapshot the result before zapping, as zapping will remove all list
* entries, i.e. checking the list later would yield a false negative.
*/
r = !list_empty(&invalid_list);
kvm_mmu_commit_zap_page(kvm, &invalid_list);
write_unlock(&kvm->mmu_lock);
out:
if (r || always_retry) {
vcpu->arch.last_retry_eip = kvm_rip_read(vcpu);
vcpu->arch.last_retry_addr = cr2_or_gpa;
}
return r;
}
static void kvm_unsync_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
trace_kvm_mmu_unsync_page(sp);
++kvm->stat.mmu_unsync;
sp->unsync = 1;
kvm_mmu_mark_parents_unsync(sp);
}
/*
* Attempt to unsync any shadow pages that can be reached by the specified gfn,
* KVM is creating a writable mapping for said gfn. Returns 0 if all pages
* were marked unsync (or if there is no shadow page), -EPERM if the SPTE must
* be write-protected.
*/
int mmu_try_to_unsync_pages(struct kvm *kvm, const struct kvm_memory_slot *slot,
gfn_t gfn, bool can_unsync, bool prefetch)
{
struct kvm_mmu_page *sp;
bool locked = false;
/*
* Force write-protection if the page is being tracked. Note, the page
* track machinery is used to write-protect upper-level shadow pages,
* i.e. this guards the role.level == 4K assertion below!
*/
if (kvm_gfn_is_write_tracked(kvm, slot, gfn))
return -EPERM;
/*
* The page is not write-tracked, mark existing shadow pages unsync
* unless KVM is synchronizing an unsync SP (can_unsync = false). In
* that case, KVM must complete emulation of the guest TLB flush before
* allowing shadow pages to become unsync (writable by the guest).
*/
for_each_gfn_valid_sp_with_gptes(kvm, sp, gfn) {
if (!can_unsync)
return -EPERM;
if (sp->unsync)
continue;
if (prefetch)
return -EEXIST;
/*
* TDP MMU page faults require an additional spinlock as they
* run with mmu_lock held for read, not write, and the unsync
* logic is not thread safe. Take the spinklock regardless of
* the MMU type to avoid extra conditionals/parameters, there's
* no meaningful penalty if mmu_lock is held for write.
*/
if (!locked) {
locked = true;
spin_lock(&kvm->arch.mmu_unsync_pages_lock);
/*
* Recheck after taking the spinlock, a different vCPU
* may have since marked the page unsync. A false
* negative on the unprotected check above is not
* possible as clearing sp->unsync _must_ hold mmu_lock
* for write, i.e. unsync cannot transition from 1->0
* while this CPU holds mmu_lock for read (or write).
*/
if (READ_ONCE(sp->unsync))
continue;
}
WARN_ON_ONCE(sp->role.level != PG_LEVEL_4K);
kvm_unsync_page(kvm, sp);
}
if (locked)
spin_unlock(&kvm->arch.mmu_unsync_pages_lock);
/*
* We need to ensure that the marking of unsync pages is visible
* before the SPTE is updated to allow writes because
* kvm_mmu_sync_roots() checks the unsync flags without holding
* the MMU lock and so can race with this. If the SPTE was updated
* before the page had been marked as unsync-ed, something like the
* following could happen:
*
* CPU 1 CPU 2
* ---------------------------------------------------------------------
* 1.2 Host updates SPTE
* to be writable
* 2.1 Guest writes a GPTE for GVA X.
* (GPTE being in the guest page table shadowed
* by the SP from CPU 1.)
* This reads SPTE during the page table walk.
* Since SPTE.W is read as 1, there is no
* fault.
*
* 2.2 Guest issues TLB flush.
* That causes a VM Exit.
*
* 2.3 Walking of unsync pages sees sp->unsync is
* false and skips the page.
*
* 2.4 Guest accesses GVA X.
* Since the mapping in the SP was not updated,
* so the old mapping for GVA X incorrectly
* gets used.
* 1.1 Host marks SP
* as unsync
* (sp->unsync = true)
*
* The write barrier below ensures that 1.1 happens before 1.2 and thus
* the situation in 2.4 does not arise. It pairs with the read barrier
* in is_unsync_root(), placed between 2.1's load of SPTE.W and 2.3.
*/
smp_wmb();
return 0;
}
static int mmu_set_spte(struct kvm_vcpu *vcpu, struct kvm_memory_slot *slot,
u64 *sptep, unsigned int pte_access, gfn_t gfn,
kvm_pfn_t pfn, struct kvm_page_fault *fault)
{
struct kvm_mmu_page *sp = sptep_to_sp(sptep);
int level = sp->role.level;
int was_rmapped = 0;
int ret = RET_PF_FIXED;
bool flush = false;
bool wrprot;
u64 spte;
/* Prefetching always gets a writable pfn. */
bool host_writable = !fault || fault->map_writable;
bool prefetch = !fault || fault->prefetch;
bool write_fault = fault && fault->write;
if (unlikely(is_noslot_pfn(pfn))) {
vcpu->stat.pf_mmio_spte_created++;
mark_mmio_spte(vcpu, sptep, gfn, pte_access);
return RET_PF_EMULATE;
}
if (is_shadow_present_pte(*sptep)) {
/*
* If we overwrite a PTE page pointer with a 2MB PMD, unlink
* the parent of the now unreachable PTE.
*/
if (level > PG_LEVEL_4K && !is_large_pte(*sptep)) {
struct kvm_mmu_page *child;
u64 pte = *sptep;
child = spte_to_child_sp(pte);
drop_parent_pte(vcpu->kvm, child, sptep);
flush = true;
} else if (pfn != spte_to_pfn(*sptep)) {
drop_spte(vcpu->kvm, sptep);
flush = true;
} else
was_rmapped = 1;
}
wrprot = make_spte(vcpu, sp, slot, pte_access, gfn, pfn, *sptep, prefetch,
true, host_writable, &spte);
if (*sptep == spte) {
ret = RET_PF_SPURIOUS;
} else {
flush |= mmu_spte_update(sptep, spte);
trace_kvm_mmu_set_spte(level, gfn, sptep);
}
if (wrprot && write_fault)
ret = RET_PF_WRITE_PROTECTED;
if (flush)
kvm_flush_remote_tlbs_gfn(vcpu->kvm, gfn, level);
if (!was_rmapped) {
WARN_ON_ONCE(ret == RET_PF_SPURIOUS);
rmap_add(vcpu, slot, sptep, gfn, pte_access);
} else {
/* Already rmapped but the pte_access bits may have changed. */
kvm_mmu_page_set_access(sp, spte_index(sptep), pte_access);
}
return ret;
}
static int direct_pte_prefetch_many(struct kvm_vcpu *vcpu,
struct kvm_mmu_page *sp,
u64 *start, u64 *end)
{
struct page *pages[PTE_PREFETCH_NUM];
struct kvm_memory_slot *slot;
unsigned int access = sp->role.access;
int i, ret;
gfn_t gfn;
gfn = kvm_mmu_page_get_gfn(sp, spte_index(start));
slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn, access & ACC_WRITE_MASK);
if (!slot)
return -1;
ret = gfn_to_page_many_atomic(slot, gfn, pages, end - start);
if (ret <= 0)
return -1;
for (i = 0; i < ret; i++, gfn++, start++) {
mmu_set_spte(vcpu, slot, start, access, gfn,
page_to_pfn(pages[i]), NULL);
put_page(pages[i]);
}
return 0;
}
static void __direct_pte_prefetch(struct kvm_vcpu *vcpu,
struct kvm_mmu_page *sp, u64 *sptep)
{
u64 *spte, *start = NULL;
int i;
WARN_ON_ONCE(!sp->role.direct);
i = spte_index(sptep) & ~(PTE_PREFETCH_NUM - 1);
spte = sp->spt + i;
for (i = 0; i < PTE_PREFETCH_NUM; i++, spte++) {
if (is_shadow_present_pte(*spte) || spte == sptep) {
if (!start)
continue;
if (direct_pte_prefetch_many(vcpu, sp, start, spte) < 0)
return;
start = NULL;
} else if (!start)
start = spte;
}
if (start)
direct_pte_prefetch_many(vcpu, sp, start, spte);
}
static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep)
{
struct kvm_mmu_page *sp;
sp = sptep_to_sp(sptep);
/*
* Without accessed bits, there's no way to distinguish between
* actually accessed translations and prefetched, so disable pte
* prefetch if accessed bits aren't available.
*/
if (sp_ad_disabled(sp))
return;
if (sp->role.level > PG_LEVEL_4K)
return;
/*
* If addresses are being invalidated, skip prefetching to avoid
* accidentally prefetching those addresses.
*/
if (unlikely(vcpu->kvm->mmu_invalidate_in_progress))
return;
__direct_pte_prefetch(vcpu, sp, sptep);
}
/*
* Lookup the mapping level for @gfn in the current mm.
*
* WARNING! Use of host_pfn_mapping_level() requires the caller and the end
* consumer to be tied into KVM's handlers for MMU notifier events!
*
* There are several ways to safely use this helper:
*
* - Check mmu_invalidate_retry_gfn() after grabbing the mapping level, before
* consuming it. In this case, mmu_lock doesn't need to be held during the
* lookup, but it does need to be held while checking the MMU notifier.
*
* - Hold mmu_lock AND ensure there is no in-progress MMU notifier invalidation
* event for the hva. This can be done by explicit checking the MMU notifier
* or by ensuring that KVM already has a valid mapping that covers the hva.
*
* - Do not use the result to install new mappings, e.g. use the host mapping
* level only to decide whether or not to zap an entry. In this case, it's
* not required to hold mmu_lock (though it's highly likely the caller will
* want to hold mmu_lock anyways, e.g. to modify SPTEs).
*
* Note! The lookup can still race with modifications to host page tables, but
* the above "rules" ensure KVM will not _consume_ the result of the walk if a
* race with the primary MMU occurs.
*/
static int host_pfn_mapping_level(struct kvm *kvm, gfn_t gfn,
const struct kvm_memory_slot *slot)
{
int level = PG_LEVEL_4K;
unsigned long hva;
unsigned long flags;
pgd_t pgd;
p4d_t p4d;
pud_t pud;
pmd_t pmd;
/*
* Note, using the already-retrieved memslot and __gfn_to_hva_memslot()
* is not solely for performance, it's also necessary to avoid the
* "writable" check in __gfn_to_hva_many(), which will always fail on
* read-only memslots due to gfn_to_hva() assuming writes. Earlier
* page fault steps have already verified the guest isn't writing a
* read-only memslot.
*/
hva = __gfn_to_hva_memslot(slot, gfn);
/*
* Disable IRQs to prevent concurrent tear down of host page tables,
* e.g. if the primary MMU promotes a P*D to a huge page and then frees
* the original page table.
*/
local_irq_save(flags);
/*
* Read each entry once. As above, a non-leaf entry can be promoted to
* a huge page _during_ this walk. Re-reading the entry could send the
* walk into the weeks, e.g. p*d_leaf() returns false (sees the old
* value) and then p*d_offset() walks into the target huge page instead
* of the old page table (sees the new value).
*/
pgd = READ_ONCE(*pgd_offset(kvm->mm, hva));
if (pgd_none(pgd))
goto out;
p4d = READ_ONCE(*p4d_offset(&pgd, hva));
if (p4d_none(p4d) || !p4d_present(p4d))
goto out;
pud = READ_ONCE(*pud_offset(&p4d, hva));
if (pud_none(pud) || !pud_present(pud))
goto out;
if (pud_leaf(pud)) {
level = PG_LEVEL_1G;
goto out;
}
pmd = READ_ONCE(*pmd_offset(&pud, hva));
if (pmd_none(pmd) || !pmd_present(pmd))
goto out;
if (pmd_leaf(pmd))
level = PG_LEVEL_2M;
out:
local_irq_restore(flags);
return level;
}
static int __kvm_mmu_max_mapping_level(struct kvm *kvm,
const struct kvm_memory_slot *slot,
gfn_t gfn, int max_level, bool is_private)
{
struct kvm_lpage_info *linfo;
int host_level;
max_level = min(max_level, max_huge_page_level);
for ( ; max_level > PG_LEVEL_4K; max_level--) {
linfo = lpage_info_slot(gfn, slot, max_level);
if (!linfo->disallow_lpage)
break;
}
if (is_private)
return max_level;
if (max_level == PG_LEVEL_4K)
return PG_LEVEL_4K;
host_level = host_pfn_mapping_level(kvm, gfn, slot);
return min(host_level, max_level);
}
int kvm_mmu_max_mapping_level(struct kvm *kvm,
const struct kvm_memory_slot *slot, gfn_t gfn,
int max_level)
{
bool is_private = kvm_slot_can_be_private(slot) &&
kvm_mem_is_private(kvm, gfn);
return __kvm_mmu_max_mapping_level(kvm, slot, gfn, max_level, is_private);
}
void kvm_mmu_hugepage_adjust(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
struct kvm_memory_slot *slot = fault->slot;
kvm_pfn_t mask;
fault->huge_page_disallowed = fault->exec && fault->nx_huge_page_workaround_enabled;
if (unlikely(fault->max_level == PG_LEVEL_4K))
return;
if (is_error_noslot_pfn(fault->pfn))
return;
if (kvm_slot_dirty_track_enabled(slot))
return;
/*
* Enforce the iTLB multihit workaround after capturing the requested
* level, which will be used to do precise, accurate accounting.
*/
fault->req_level = __kvm_mmu_max_mapping_level(vcpu->kvm, slot,
fault->gfn, fault->max_level,
fault->is_private);
if (fault->req_level == PG_LEVEL_4K || fault->huge_page_disallowed)
return;
/*
* mmu_invalidate_retry() was successful and mmu_lock is held, so
* the pmd can't be split from under us.
*/
fault->goal_level = fault->req_level;
mask = KVM_PAGES_PER_HPAGE(fault->goal_level) - 1;
VM_BUG_ON((fault->gfn & mask) != (fault->pfn & mask));
fault->pfn &= ~mask;
}
void disallowed_hugepage_adjust(struct kvm_page_fault *fault, u64 spte, int cur_level)
{
if (cur_level > PG_LEVEL_4K &&
cur_level == fault->goal_level &&
is_shadow_present_pte(spte) &&
!is_large_pte(spte) &&
spte_to_child_sp(spte)->nx_huge_page_disallowed) {
/*
* A small SPTE exists for this pfn, but FNAME(fetch),
* direct_map(), or kvm_tdp_mmu_map() would like to create a
* large PTE instead: just force them to go down another level,
* patching back for them into pfn the next 9 bits of the
* address.
*/
u64 page_mask = KVM_PAGES_PER_HPAGE(cur_level) -
KVM_PAGES_PER_HPAGE(cur_level - 1);
fault->pfn |= fault->gfn & page_mask;
fault->goal_level--;
}
}
static int direct_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
struct kvm_shadow_walk_iterator it;
struct kvm_mmu_page *sp;
int ret;
gfn_t base_gfn = fault->gfn;
kvm_mmu_hugepage_adjust(vcpu, fault);
trace_kvm_mmu_spte_requested(fault);
for_each_shadow_entry(vcpu, fault->addr, it) {
/*
* We cannot overwrite existing page tables with an NX
* large page, as the leaf could be executable.
*/
if (fault->nx_huge_page_workaround_enabled)
disallowed_hugepage_adjust(fault, *it.sptep, it.level);
base_gfn = gfn_round_for_level(fault->gfn, it.level);
if (it.level == fault->goal_level)
break;
sp = kvm_mmu_get_child_sp(vcpu, it.sptep, base_gfn, true, ACC_ALL);
if (sp == ERR_PTR(-EEXIST))
continue;
link_shadow_page(vcpu, it.sptep, sp);
if (fault->huge_page_disallowed)
account_nx_huge_page(vcpu->kvm, sp,
fault->req_level >= it.level);
}
if (WARN_ON_ONCE(it.level != fault->goal_level))
return -EFAULT;
ret = mmu_set_spte(vcpu, fault->slot, it.sptep, ACC_ALL,
base_gfn, fault->pfn, fault);
if (ret == RET_PF_SPURIOUS)
return ret;
direct_pte_prefetch(vcpu, it.sptep);
return ret;
}
static void kvm_send_hwpoison_signal(struct kvm_memory_slot *slot, gfn_t gfn)
{
unsigned long hva = gfn_to_hva_memslot(slot, gfn);
send_sig_mceerr(BUS_MCEERR_AR, (void __user *)hva, PAGE_SHIFT, current);
}
static int kvm_handle_error_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
if (is_sigpending_pfn(fault->pfn)) {
kvm_handle_signal_exit(vcpu);
return -EINTR;
}
/*
* Do not cache the mmio info caused by writing the readonly gfn
* into the spte otherwise read access on readonly gfn also can
* caused mmio page fault and treat it as mmio access.
*/
if (fault->pfn == KVM_PFN_ERR_RO_FAULT)
return RET_PF_EMULATE;
if (fault->pfn == KVM_PFN_ERR_HWPOISON) {
kvm_send_hwpoison_signal(fault->slot, fault->gfn);
return RET_PF_RETRY;
}
return -EFAULT;
}
static int kvm_handle_noslot_fault(struct kvm_vcpu *vcpu,
struct kvm_page_fault *fault,
unsigned int access)
{
gva_t gva = fault->is_tdp ? 0 : fault->addr;
if (fault->is_private) {
kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
return -EFAULT;
}
vcpu_cache_mmio_info(vcpu, gva, fault->gfn,
access & shadow_mmio_access_mask);
fault->slot = NULL;
fault->pfn = KVM_PFN_NOSLOT;
fault->map_writable = false;
fault->hva = KVM_HVA_ERR_BAD;
/*
* If MMIO caching is disabled, emulate immediately without
* touching the shadow page tables as attempting to install an
* MMIO SPTE will just be an expensive nop.
*/
if (unlikely(!enable_mmio_caching))
return RET_PF_EMULATE;
/*
* Do not create an MMIO SPTE for a gfn greater than host.MAXPHYADDR,
* any guest that generates such gfns is running nested and is being
* tricked by L0 userspace (you can observe gfn > L1.MAXPHYADDR if and
* only if L1's MAXPHYADDR is inaccurate with respect to the
* hardware's).
*/
if (unlikely(fault->gfn > kvm_mmu_max_gfn()))
return RET_PF_EMULATE;
return RET_PF_CONTINUE;
}
static bool page_fault_can_be_fast(struct kvm *kvm, struct kvm_page_fault *fault)
{
/*
* Page faults with reserved bits set, i.e. faults on MMIO SPTEs, only
* reach the common page fault handler if the SPTE has an invalid MMIO
* generation number. Refreshing the MMIO generation needs to go down
* the slow path. Note, EPT Misconfigs do NOT set the PRESENT flag!
*/
if (fault->rsvd)
return false;
/*
* For hardware-protected VMs, certain conditions like attempting to
* perform a write to a page which is not in the state that the guest
* expects it to be in can result in a nested/extended #PF. In this
* case, the below code might misconstrue this situation as being the
* result of a write-protected access, and treat it as a spurious case
* rather than taking any action to satisfy the real source of the #PF
* such as generating a KVM_EXIT_MEMORY_FAULT. This can lead to the
* guest spinning on a #PF indefinitely, so don't attempt the fast path
* in this case.
*
* Note that the kvm_mem_is_private() check might race with an
* attribute update, but this will either result in the guest spinning
* on RET_PF_SPURIOUS until the update completes, or an actual spurious
* case might go down the slow path. Either case will resolve itself.
*/
if (kvm->arch.has_private_mem &&
fault->is_private != kvm_mem_is_private(kvm, fault->gfn))
return false;
/*
* #PF can be fast if:
*
* 1. The shadow page table entry is not present and A/D bits are
* disabled _by KVM_, which could mean that the fault is potentially
* caused by access tracking (if enabled). If A/D bits are enabled
* by KVM, but disabled by L1 for L2, KVM is forced to disable A/D
* bits for L2 and employ access tracking, but the fast page fault
* mechanism only supports direct MMUs.
* 2. The shadow page table entry is present, the access is a write,
* and no reserved bits are set (MMIO SPTEs cannot be "fixed"), i.e.
* the fault was caused by a write-protection violation. If the
* SPTE is MMU-writable (determined later), the fault can be fixed
* by setting the Writable bit, which can be done out of mmu_lock.
*/
if (!fault->present)
return !kvm_ad_enabled();
/*
* Note, instruction fetches and writes are mutually exclusive, ignore
* the "exec" flag.
*/
return fault->write;
}
/*
* Returns true if the SPTE was fixed successfully. Otherwise,
* someone else modified the SPTE from its original value.
*/
static bool fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu,
struct kvm_page_fault *fault,
u64 *sptep, u64 old_spte, u64 new_spte)
{
/*
* Theoretically we could also set dirty bit (and flush TLB) here in
* order to eliminate unnecessary PML logging. See comments in
* set_spte. But fast_page_fault is very unlikely to happen with PML
* enabled, so we do not do this. This might result in the same GPA
* to be logged in PML buffer again when the write really happens, and
* eventually to be called by mark_page_dirty twice. But it's also no
* harm. This also avoids the TLB flush needed after setting dirty bit
* so non-PML cases won't be impacted.
*
* Compare with set_spte where instead shadow_dirty_mask is set.
*/
if (!try_cmpxchg64(sptep, &old_spte, new_spte))
return false;
if (is_writable_pte(new_spte) && !is_writable_pte(old_spte))
mark_page_dirty_in_slot(vcpu->kvm, fault->slot, fault->gfn);
return true;
}
static bool is_access_allowed(struct kvm_page_fault *fault, u64 spte)
{
if (fault->exec)
return is_executable_pte(spte);
if (fault->write)
return is_writable_pte(spte);
/* Fault was on Read access */
return spte & PT_PRESENT_MASK;
}
/*
* Returns the last level spte pointer of the shadow page walk for the given
* gpa, and sets *spte to the spte value. This spte may be non-preset. If no
* walk could be performed, returns NULL and *spte does not contain valid data.
*
* Contract:
* - Must be called between walk_shadow_page_lockless_{begin,end}.
* - The returned sptep must not be used after walk_shadow_page_lockless_end.
*/
static u64 *fast_pf_get_last_sptep(struct kvm_vcpu *vcpu, gpa_t gpa, u64 *spte)
{
struct kvm_shadow_walk_iterator iterator;
u64 old_spte;
u64 *sptep = NULL;
for_each_shadow_entry_lockless(vcpu, gpa, iterator, old_spte) {
sptep = iterator.sptep;
*spte = old_spte;
}
return sptep;
}
/*
* Returns one of RET_PF_INVALID, RET_PF_FIXED or RET_PF_SPURIOUS.
*/
static int fast_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
struct kvm_mmu_page *sp;
int ret = RET_PF_INVALID;
u64 spte;
u64 *sptep;
uint retry_count = 0;
if (!page_fault_can_be_fast(vcpu->kvm, fault))
return ret;
walk_shadow_page_lockless_begin(vcpu);
do {
u64 new_spte;
if (tdp_mmu_enabled)
sptep = kvm_tdp_mmu_fast_pf_get_last_sptep(vcpu, fault->gfn, &spte);
else
sptep = fast_pf_get_last_sptep(vcpu, fault->addr, &spte);
/*
* It's entirely possible for the mapping to have been zapped
* by a different task, but the root page should always be
* available as the vCPU holds a reference to its root(s).
*/
if (WARN_ON_ONCE(!sptep))
spte = FROZEN_SPTE;
if (!is_shadow_present_pte(spte))
break;
sp = sptep_to_sp(sptep);
if (!is_last_spte(spte, sp->role.level))
break;
/*
* Check whether the memory access that caused the fault would
* still cause it if it were to be performed right now. If not,
* then this is a spurious fault caused by TLB lazily flushed,
* or some other CPU has already fixed the PTE after the
* current CPU took the fault.
*
* Need not check the access of upper level table entries since
* they are always ACC_ALL.
*/
if (is_access_allowed(fault, spte)) {
ret = RET_PF_SPURIOUS;
break;
}
new_spte = spte;
/*
* KVM only supports fixing page faults outside of MMU lock for
* direct MMUs, nested MMUs are always indirect, and KVM always
* uses A/D bits for non-nested MMUs. Thus, if A/D bits are
* enabled, the SPTE can't be an access-tracked SPTE.
*/
if (unlikely(!kvm_ad_enabled()) && is_access_track_spte(spte))
new_spte = restore_acc_track_spte(new_spte);
/*
* To keep things simple, only SPTEs that are MMU-writable can
* be made fully writable outside of mmu_lock, e.g. only SPTEs
* that were write-protected for dirty-logging or access
* tracking are handled here. Don't bother checking if the
* SPTE is writable to prioritize running with A/D bits enabled.
* The is_access_allowed() check above handles the common case
* of the fault being spurious, and the SPTE is known to be
* shadow-present, i.e. except for access tracking restoration
* making the new SPTE writable, the check is wasteful.
*/
if (fault->write && is_mmu_writable_spte(spte)) {
new_spte |= PT_WRITABLE_MASK;
/*
* Do not fix write-permission on the large spte when
* dirty logging is enabled. Since we only dirty the
* first page into the dirty-bitmap in
* fast_pf_fix_direct_spte(), other pages are missed
* if its slot has dirty logging enabled.
*
* Instead, we let the slow page fault path create a
* normal spte to fix the access.
*/
if (sp->role.level > PG_LEVEL_4K &&
kvm_slot_dirty_track_enabled(fault->slot))
break;
}
/* Verify that the fault can be handled in the fast path */
if (new_spte == spte ||
!is_access_allowed(fault, new_spte))
break;
/*
* Currently, fast page fault only works for direct mapping
* since the gfn is not stable for indirect shadow page. See
* Documentation/virt/kvm/locking.rst to get more detail.
*/
if (fast_pf_fix_direct_spte(vcpu, fault, sptep, spte, new_spte)) {
ret = RET_PF_FIXED;
break;
}
if (++retry_count > 4) {
pr_warn_once("Fast #PF retrying more than 4 times.\n");
break;
}
} while (true);
trace_fast_page_fault(vcpu, fault, sptep, spte, ret);
walk_shadow_page_lockless_end(vcpu);
if (ret != RET_PF_INVALID)
vcpu->stat.pf_fast++;
return ret;
}
static void mmu_free_root_page(struct kvm *kvm, hpa_t *root_hpa,
struct list_head *invalid_list)
{
struct kvm_mmu_page *sp;
if (!VALID_PAGE(*root_hpa))
return;
sp = root_to_sp(*root_hpa);
if (WARN_ON_ONCE(!sp))
return;
if (is_tdp_mmu_page(sp)) {
lockdep_assert_held_read(&kvm->mmu_lock);
kvm_tdp_mmu_put_root(kvm, sp);
} else {
lockdep_assert_held_write(&kvm->mmu_lock);
if (!--sp->root_count && sp->role.invalid)
kvm_mmu_prepare_zap_page(kvm, sp, invalid_list);
}
*root_hpa = INVALID_PAGE;
}
/* roots_to_free must be some combination of the KVM_MMU_ROOT_* flags */
void kvm_mmu_free_roots(struct kvm *kvm, struct kvm_mmu *mmu,
ulong roots_to_free)
{
bool is_tdp_mmu = tdp_mmu_enabled && mmu->root_role.direct;
int i;
LIST_HEAD(invalid_list);
bool free_active_root;
WARN_ON_ONCE(roots_to_free & ~KVM_MMU_ROOTS_ALL);
BUILD_BUG_ON(KVM_MMU_NUM_PREV_ROOTS >= BITS_PER_LONG);
/* Before acquiring the MMU lock, see if we need to do any real work. */
free_active_root = (roots_to_free & KVM_MMU_ROOT_CURRENT)
&& VALID_PAGE(mmu->root.hpa);
if (!free_active_root) {
for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
if ((roots_to_free & KVM_MMU_ROOT_PREVIOUS(i)) &&
VALID_PAGE(mmu->prev_roots[i].hpa))
break;
if (i == KVM_MMU_NUM_PREV_ROOTS)
return;
}
if (is_tdp_mmu)
read_lock(&kvm->mmu_lock);
else
write_lock(&kvm->mmu_lock);
for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
if (roots_to_free & KVM_MMU_ROOT_PREVIOUS(i))
mmu_free_root_page(kvm, &mmu->prev_roots[i].hpa,
&invalid_list);
if (free_active_root) {
if (kvm_mmu_is_dummy_root(mmu->root.hpa)) {
/* Nothing to cleanup for dummy roots. */
} else if (root_to_sp(mmu->root.hpa)) {
mmu_free_root_page(kvm, &mmu->root.hpa, &invalid_list);
} else if (mmu->pae_root) {
for (i = 0; i < 4; ++i) {
if (!IS_VALID_PAE_ROOT(mmu->pae_root[i]))
continue;
mmu_free_root_page(kvm, &mmu->pae_root[i],
&invalid_list);
mmu->pae_root[i] = INVALID_PAE_ROOT;
}
}
mmu->root.hpa = INVALID_PAGE;
mmu->root.pgd = 0;
}
if (is_tdp_mmu) {
read_unlock(&kvm->mmu_lock);
WARN_ON_ONCE(!list_empty(&invalid_list));
} else {
kvm_mmu_commit_zap_page(kvm, &invalid_list);
write_unlock(&kvm->mmu_lock);
}
}
EXPORT_SYMBOL_GPL(kvm_mmu_free_roots);
void kvm_mmu_free_guest_mode_roots(struct kvm *kvm, struct kvm_mmu *mmu)
{
unsigned long roots_to_free = 0;
struct kvm_mmu_page *sp;
hpa_t root_hpa;
int i;
/*
* This should not be called while L2 is active, L2 can't invalidate
* _only_ its own roots, e.g. INVVPID unconditionally exits.
*/
WARN_ON_ONCE(mmu->root_role.guest_mode);
for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) {
root_hpa = mmu->prev_roots[i].hpa;
if (!VALID_PAGE(root_hpa))
continue;
sp = root_to_sp(root_hpa);
if (!sp || sp->role.guest_mode)
roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i);
}
kvm_mmu_free_roots(kvm, mmu, roots_to_free);
}
EXPORT_SYMBOL_GPL(kvm_mmu_free_guest_mode_roots);
static hpa_t mmu_alloc_root(struct kvm_vcpu *vcpu, gfn_t gfn, int quadrant,
u8 level)
{
union kvm_mmu_page_role role = vcpu->arch.mmu->root_role;
struct kvm_mmu_page *sp;
role.level = level;
role.quadrant = quadrant;
WARN_ON_ONCE(quadrant && !role.has_4_byte_gpte);
WARN_ON_ONCE(role.direct && role.has_4_byte_gpte);
sp = kvm_mmu_get_shadow_page(vcpu, gfn, role);
++sp->root_count;
return __pa(sp->spt);
}
static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
{
struct kvm_mmu *mmu = vcpu->arch.mmu;
u8 shadow_root_level = mmu->root_role.level;
hpa_t root;
unsigned i;
int r;
if (tdp_mmu_enabled)
return kvm_tdp_mmu_alloc_root(vcpu);
write_lock(&vcpu->kvm->mmu_lock);
r = make_mmu_pages_available(vcpu);
if (r < 0)
goto out_unlock;
if (shadow_root_level >= PT64_ROOT_4LEVEL) {
root = mmu_alloc_root(vcpu, 0, 0, shadow_root_level);
mmu->root.hpa = root;
} else if (shadow_root_level == PT32E_ROOT_LEVEL) {
if (WARN_ON_ONCE(!mmu->pae_root)) {
r = -EIO;
goto out_unlock;
}
for (i = 0; i < 4; ++i) {
WARN_ON_ONCE(IS_VALID_PAE_ROOT(mmu->pae_root[i]));
root = mmu_alloc_root(vcpu, i << (30 - PAGE_SHIFT), 0,
PT32_ROOT_LEVEL);
mmu->pae_root[i] = root | PT_PRESENT_MASK |
shadow_me_value;
}
mmu->root.hpa = __pa(mmu->pae_root);
} else {
WARN_ONCE(1, "Bad TDP root level = %d\n", shadow_root_level);
r = -EIO;
goto out_unlock;
}
/* root.pgd is ignored for direct MMUs. */
mmu->root.pgd = 0;
out_unlock:
write_unlock(&vcpu->kvm->mmu_lock);
return r;
}
static int mmu_first_shadow_root_alloc(struct kvm *kvm)
{
struct kvm_memslots *slots;
struct kvm_memory_slot *slot;
int r = 0, i, bkt;
/*
* Check if this is the first shadow root being allocated before
* taking the lock.
*/
if (kvm_shadow_root_allocated(kvm))
return 0;
mutex_lock(&kvm->slots_arch_lock);
/* Recheck, under the lock, whether this is the first shadow root. */
if (kvm_shadow_root_allocated(kvm))
goto out_unlock;
/*
* Check if anything actually needs to be allocated, e.g. all metadata
* will be allocated upfront if TDP is disabled.
*/
if (kvm_memslots_have_rmaps(kvm) &&
kvm_page_track_write_tracking_enabled(kvm))
goto out_success;
for (i = 0; i < kvm_arch_nr_memslot_as_ids(kvm); i++) {
slots = __kvm_memslots(kvm, i);
kvm_for_each_memslot(slot, bkt, slots) {
/*
* Both of these functions are no-ops if the target is
* already allocated, so unconditionally calling both
* is safe. Intentionally do NOT free allocations on
* failure to avoid having to track which allocations
* were made now versus when the memslot was created.
* The metadata is guaranteed to be freed when the slot
* is freed, and will be kept/used if userspace retries
* KVM_RUN instead of killing the VM.
*/
r = memslot_rmap_alloc(slot, slot->npages);
if (r)
goto out_unlock;
r = kvm_page_track_write_tracking_alloc(slot);
if (r)
goto out_unlock;
}
}
/*
* Ensure that shadow_root_allocated becomes true strictly after
* all the related pointers are set.
*/
out_success:
smp_store_release(&kvm->arch.shadow_root_allocated, true);
out_unlock:
mutex_unlock(&kvm->slots_arch_lock);
return r;
}
static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
{
struct kvm_mmu *mmu = vcpu->arch.mmu;
u64 pdptrs[4], pm_mask;
gfn_t root_gfn, root_pgd;
int quadrant, i, r;
hpa_t root;
root_pgd = kvm_mmu_get_guest_pgd(vcpu, mmu);
root_gfn = (root_pgd & __PT_BASE_ADDR_MASK) >> PAGE_SHIFT;
if (!kvm_vcpu_is_visible_gfn(vcpu, root_gfn)) {
mmu->root.hpa = kvm_mmu_get_dummy_root();
return 0;
}
/*
* On SVM, reading PDPTRs might access guest memory, which might fault
* and thus might sleep. Grab the PDPTRs before acquiring mmu_lock.
*/
if (mmu->cpu_role.base.level == PT32E_ROOT_LEVEL) {
for (i = 0; i < 4; ++i) {
pdptrs[i] = mmu->get_pdptr(vcpu, i);
if (!(pdptrs[i] & PT_PRESENT_MASK))
continue;
if (!kvm_vcpu_is_visible_gfn(vcpu, pdptrs[i] >> PAGE_SHIFT))
pdptrs[i] = 0;
}
}
r = mmu_first_shadow_root_alloc(vcpu->kvm);
if (r)
return r;
write_lock(&vcpu->kvm->mmu_lock);
r = make_mmu_pages_available(vcpu);
if (r < 0)
goto out_unlock;
/*
* Do we shadow a long mode page table? If so we need to
* write-protect the guests page table root.
*/
if (mmu->cpu_role.base.level >= PT64_ROOT_4LEVEL) {
root = mmu_alloc_root(vcpu, root_gfn, 0,
mmu->root_role.level);
mmu->root.hpa = root;
goto set_root_pgd;
}
if (WARN_ON_ONCE(!mmu->pae_root)) {
r = -EIO;
goto out_unlock;
}
/*
* We shadow a 32 bit page table. This may be a legacy 2-level
* or a PAE 3-level page table. In either case we need to be aware that
* the shadow page table may be a PAE or a long mode page table.
*/
pm_mask = PT_PRESENT_MASK | shadow_me_value;
if (mmu->root_role.level >= PT64_ROOT_4LEVEL) {
pm_mask |= PT_ACCESSED_MASK | PT_WRITABLE_MASK | PT_USER_MASK;
if (WARN_ON_ONCE(!mmu->pml4_root)) {
r = -EIO;
goto out_unlock;
}
mmu->pml4_root[0] = __pa(mmu->pae_root) | pm_mask;
if (mmu->root_role.level == PT64_ROOT_5LEVEL) {
if (WARN_ON_ONCE(!mmu->pml5_root)) {
r = -EIO;
goto out_unlock;
}
mmu->pml5_root[0] = __pa(mmu->pml4_root) | pm_mask;
}
}
for (i = 0; i < 4; ++i) {
WARN_ON_ONCE(IS_VALID_PAE_ROOT(mmu->pae_root[i]));
if (mmu->cpu_role.base.level == PT32E_ROOT_LEVEL) {
if (!(pdptrs[i] & PT_PRESENT_MASK)) {
mmu->pae_root[i] = INVALID_PAE_ROOT;
continue;
}
root_gfn = pdptrs[i] >> PAGE_SHIFT;
}
/*
* If shadowing 32-bit non-PAE page tables, each PAE page
* directory maps one quarter of the guest's non-PAE page
* directory. Othwerise each PAE page direct shadows one guest
* PAE page directory so that quadrant should be 0.
*/
quadrant = (mmu->cpu_role.base.level == PT32_ROOT_LEVEL) ? i : 0;
root = mmu_alloc_root(vcpu, root_gfn, quadrant, PT32_ROOT_LEVEL);
mmu->pae_root[i] = root | pm_mask;
}
if (mmu->root_role.level == PT64_ROOT_5LEVEL)
mmu->root.hpa = __pa(mmu->pml5_root);
else if (mmu->root_role.level == PT64_ROOT_4LEVEL)
mmu->root.hpa = __pa(mmu->pml4_root);
else
mmu->root.hpa = __pa(mmu->pae_root);
set_root_pgd:
mmu->root.pgd = root_pgd;
out_unlock:
write_unlock(&vcpu->kvm->mmu_lock);
return r;
}
static int mmu_alloc_special_roots(struct kvm_vcpu *vcpu)
{
struct kvm_mmu *mmu = vcpu->arch.mmu;
bool need_pml5 = mmu->root_role.level > PT64_ROOT_4LEVEL;
u64 *pml5_root = NULL;
u64 *pml4_root = NULL;
u64 *pae_root;
/*
* When shadowing 32-bit or PAE NPT with 64-bit NPT, the PML4 and PDP
* tables are allocated and initialized at root creation as there is no
* equivalent level in the guest's NPT to shadow. Allocate the tables
* on demand, as running a 32-bit L1 VMM on 64-bit KVM is very rare.
*/
if (mmu->root_role.direct ||
mmu->cpu_role.base.level >= PT64_ROOT_4LEVEL ||
mmu->root_role.level < PT64_ROOT_4LEVEL)
return 0;
/*
* NPT, the only paging mode that uses this horror, uses a fixed number
* of levels for the shadow page tables, e.g. all MMUs are 4-level or
* all MMus are 5-level. Thus, this can safely require that pml5_root
* is allocated if the other roots are valid and pml5 is needed, as any
* prior MMU would also have required pml5.
*/
if (mmu->pae_root && mmu->pml4_root && (!need_pml5 || mmu->pml5_root))
return 0;
/*
* The special roots should always be allocated in concert. Yell and
* bail if KVM ends up in a state where only one of the roots is valid.
*/
if (WARN_ON_ONCE(!tdp_enabled || mmu->pae_root || mmu->pml4_root ||
(need_pml5 && mmu->pml5_root)))
return -EIO;
/*
* Unlike 32-bit NPT, the PDP table doesn't need to be in low mem, and
* doesn't need to be decrypted.
*/
pae_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
if (!pae_root)
return -ENOMEM;
#ifdef CONFIG_X86_64
pml4_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
if (!pml4_root)
goto err_pml4;
if (need_pml5) {
pml5_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
if (!pml5_root)
goto err_pml5;
}
#endif
mmu->pae_root = pae_root;
mmu->pml4_root = pml4_root;
mmu->pml5_root = pml5_root;
return 0;
#ifdef CONFIG_X86_64
err_pml5:
free_page((unsigned long)pml4_root);
err_pml4:
free_page((unsigned long)pae_root);
return -ENOMEM;
#endif
}
static bool is_unsync_root(hpa_t root)
{
struct kvm_mmu_page *sp;
if (!VALID_PAGE(root) || kvm_mmu_is_dummy_root(root))
return false;
/*
* The read barrier orders the CPU's read of SPTE.W during the page table
* walk before the reads of sp->unsync/sp->unsync_children here.
*
* Even if another CPU was marking the SP as unsync-ed simultaneously,
* any guest page table changes are not guaranteed to be visible anyway
* until this VCPU issues a TLB flush strictly after those changes are
* made. We only need to ensure that the other CPU sets these flags
* before any actual changes to the page tables are made. The comments
* in mmu_try_to_unsync_pages() describe what could go wrong if this
* requirement isn't satisfied.
*/
smp_rmb();
sp = root_to_sp(root);
/*
* PAE roots (somewhat arbitrarily) aren't backed by shadow pages, the
* PDPTEs for a given PAE root need to be synchronized individually.
*/
if (WARN_ON_ONCE(!sp))
return false;
if (sp->unsync || sp->unsync_children)
return true;
return false;
}
void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu)
{
int i;
struct kvm_mmu_page *sp;
if (vcpu->arch.mmu->root_role.direct)
return;
if (!VALID_PAGE(vcpu->arch.mmu->root.hpa))
return;
vcpu_clear_mmio_info(vcpu, MMIO_GVA_ANY);
if (vcpu->arch.mmu->cpu_role.base.level >= PT64_ROOT_4LEVEL) {
hpa_t root = vcpu->arch.mmu->root.hpa;
if (!is_unsync_root(root))
return;
sp = root_to_sp(root);
write_lock(&vcpu->kvm->mmu_lock);
mmu_sync_children(vcpu, sp, true);
write_unlock(&vcpu->kvm->mmu_lock);
return;
}
write_lock(&vcpu->kvm->mmu_lock);
for (i = 0; i < 4; ++i) {
hpa_t root = vcpu->arch.mmu->pae_root[i];
if (IS_VALID_PAE_ROOT(root)) {
sp = spte_to_child_sp(root);
mmu_sync_children(vcpu, sp, true);
}
}
write_unlock(&vcpu->kvm->mmu_lock);
}
void kvm_mmu_sync_prev_roots(struct kvm_vcpu *vcpu)
{
unsigned long roots_to_free = 0;
int i;
for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
if (is_unsync_root(vcpu->arch.mmu->prev_roots[i].hpa))
roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i);
/* sync prev_roots by simply freeing them */
kvm_mmu_free_roots(vcpu->kvm, vcpu->arch.mmu, roots_to_free);
}
static gpa_t nonpaging_gva_to_gpa(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
gpa_t vaddr, u64 access,
struct x86_exception *exception)
{
if (exception)
exception->error_code = 0;
return kvm_translate_gpa(vcpu, mmu, vaddr, access, exception);
}
static bool mmio_info_in_cache(struct kvm_vcpu *vcpu, u64 addr, bool direct)
{
/*
* A nested guest cannot use the MMIO cache if it is using nested
* page tables, because cr2 is a nGPA while the cache stores GPAs.
*/
if (mmu_is_nested(vcpu))
return false;
if (direct)
return vcpu_match_mmio_gpa(vcpu, addr);
return vcpu_match_mmio_gva(vcpu, addr);
}
/*
* Return the level of the lowest level SPTE added to sptes.
* That SPTE may be non-present.
*
* Must be called between walk_shadow_page_lockless_{begin,end}.
*/
static int get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, int *root_level)
{
struct kvm_shadow_walk_iterator iterator;
int leaf = -1;
u64 spte;
for (shadow_walk_init(&iterator, vcpu, addr),
*root_level = iterator.level;
shadow_walk_okay(&iterator);
__shadow_walk_next(&iterator, spte)) {
leaf = iterator.level;
spte = mmu_spte_get_lockless(iterator.sptep);
sptes[leaf] = spte;
}
return leaf;
}
static int get_sptes_lockless(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes,
int *root_level)
{
int leaf;
walk_shadow_page_lockless_begin(vcpu);
if (is_tdp_mmu_active(vcpu))
leaf = kvm_tdp_mmu_get_walk(vcpu, addr, sptes, root_level);
else
leaf = get_walk(vcpu, addr, sptes, root_level);
walk_shadow_page_lockless_end(vcpu);
return leaf;
}
/* return true if reserved bit(s) are detected on a valid, non-MMIO SPTE. */
static bool get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep)
{
u64 sptes[PT64_ROOT_MAX_LEVEL + 1];
struct rsvd_bits_validate *rsvd_check;
int root, leaf, level;
bool reserved = false;
leaf = get_sptes_lockless(vcpu, addr, sptes, &root);
if (unlikely(leaf < 0)) {
*sptep = 0ull;
return reserved;
}
*sptep = sptes[leaf];
/*
* Skip reserved bits checks on the terminal leaf if it's not a valid
* SPTE. Note, this also (intentionally) skips MMIO SPTEs, which, by
* design, always have reserved bits set. The purpose of the checks is
* to detect reserved bits on non-MMIO SPTEs. i.e. buggy SPTEs.
*/
if (!is_shadow_present_pte(sptes[leaf]))
leaf++;
rsvd_check = &vcpu->arch.mmu->shadow_zero_check;
for (level = root; level >= leaf; level--)
reserved |= is_rsvd_spte(rsvd_check, sptes[level], level);
if (reserved) {
pr_err("%s: reserved bits set on MMU-present spte, addr 0x%llx, hierarchy:\n",
__func__, addr);
for (level = root; level >= leaf; level--)
pr_err("------ spte = 0x%llx level = %d, rsvd bits = 0x%llx",
sptes[level], level,
get_rsvd_bits(rsvd_check, sptes[level], level));
}
return reserved;
}
static int handle_mmio_page_fault(struct kvm_vcpu *vcpu, u64 addr, bool direct)
{
u64 spte;
bool reserved;
if (mmio_info_in_cache(vcpu, addr, direct))
return RET_PF_EMULATE;
reserved = get_mmio_spte(vcpu, addr, &spte);
if (WARN_ON_ONCE(reserved))
return -EINVAL;
if (is_mmio_spte(vcpu->kvm, spte)) {
gfn_t gfn = get_mmio_spte_gfn(spte);
unsigned int access = get_mmio_spte_access(spte);
if (!check_mmio_spte(vcpu, spte))
return RET_PF_INVALID;
if (direct)
addr = 0;
trace_handle_mmio_page_fault(addr, gfn, access);
vcpu_cache_mmio_info(vcpu, addr, gfn, access);
return RET_PF_EMULATE;
}
/*
* If the page table is zapped by other cpus, let CPU fault again on
* the address.
*/
return RET_PF_RETRY;
}
static bool page_fault_handle_page_track(struct kvm_vcpu *vcpu,
struct kvm_page_fault *fault)
{
if (unlikely(fault->rsvd))
return false;
if (!fault->present || !fault->write)
return false;
/*
* guest is writing the page which is write tracked which can
* not be fixed by page fault handler.
*/
if (kvm_gfn_is_write_tracked(vcpu->kvm, fault->slot, fault->gfn))
return true;
return false;
}
static void shadow_page_table_clear_flood(struct kvm_vcpu *vcpu, gva_t addr)
{
struct kvm_shadow_walk_iterator iterator;
u64 spte;
walk_shadow_page_lockless_begin(vcpu);
for_each_shadow_entry_lockless(vcpu, addr, iterator, spte)
clear_sp_write_flooding_count(iterator.sptep);
walk_shadow_page_lockless_end(vcpu);
}
static u32 alloc_apf_token(struct kvm_vcpu *vcpu)
{
/* make sure the token value is not 0 */
u32 id = vcpu->arch.apf.id;
if (id << 12 == 0)
vcpu->arch.apf.id = 1;
return (vcpu->arch.apf.id++ << 12) | vcpu->vcpu_id;
}
static bool kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu,
struct kvm_page_fault *fault)
{
struct kvm_arch_async_pf arch;
arch.token = alloc_apf_token(vcpu);
arch.gfn = fault->gfn;
arch.error_code = fault->error_code;
arch.direct_map = vcpu->arch.mmu->root_role.direct;
arch.cr3 = kvm_mmu_get_guest_pgd(vcpu, vcpu->arch.mmu);
return kvm_setup_async_pf(vcpu, fault->addr,
kvm_vcpu_gfn_to_hva(vcpu, fault->gfn), &arch);
}
void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
{
int r;
if (WARN_ON_ONCE(work->arch.error_code & PFERR_PRIVATE_ACCESS))
return;
if ((vcpu->arch.mmu->root_role.direct != work->arch.direct_map) ||
work->wakeup_all)
return;
r = kvm_mmu_reload(vcpu);
if (unlikely(r))
return;
if (!vcpu->arch.mmu->root_role.direct &&
work->arch.cr3 != kvm_mmu_get_guest_pgd(vcpu, vcpu->arch.mmu))
return;
r = kvm_mmu_do_page_fault(vcpu, work->cr2_or_gpa, work->arch.error_code,
true, NULL, NULL);
/*
* Account fixed page faults, otherwise they'll never be counted, but
* ignore stats for all other return times. Page-ready "faults" aren't
* truly spurious and never trigger emulation
*/
if (r == RET_PF_FIXED)
vcpu->stat.pf_fixed++;
}
static inline u8 kvm_max_level_for_order(int order)
{
BUILD_BUG_ON(KVM_MAX_HUGEPAGE_LEVEL > PG_LEVEL_1G);
KVM_MMU_WARN_ON(order != KVM_HPAGE_GFN_SHIFT(PG_LEVEL_1G) &&
order != KVM_HPAGE_GFN_SHIFT(PG_LEVEL_2M) &&
order != KVM_HPAGE_GFN_SHIFT(PG_LEVEL_4K));
if (order >= KVM_HPAGE_GFN_SHIFT(PG_LEVEL_1G))
return PG_LEVEL_1G;
if (order >= KVM_HPAGE_GFN_SHIFT(PG_LEVEL_2M))
return PG_LEVEL_2M;
return PG_LEVEL_4K;
}
static u8 kvm_max_private_mapping_level(struct kvm *kvm, kvm_pfn_t pfn,
u8 max_level, int gmem_order)
{
u8 req_max_level;
if (max_level == PG_LEVEL_4K)
return PG_LEVEL_4K;
max_level = min(kvm_max_level_for_order(gmem_order), max_level);
if (max_level == PG_LEVEL_4K)
return PG_LEVEL_4K;
req_max_level = kvm_x86_call(private_max_mapping_level)(kvm, pfn);
if (req_max_level)
max_level = min(max_level, req_max_level);
return max_level;
}
static int kvm_faultin_pfn_private(struct kvm_vcpu *vcpu,
struct kvm_page_fault *fault)
{
int max_order, r;
if (!kvm_slot_can_be_private(fault->slot)) {
kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
return -EFAULT;
}
r = kvm_gmem_get_pfn(vcpu->kvm, fault->slot, fault->gfn, &fault->pfn,
&max_order);
if (r) {
kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
return r;
}
fault->map_writable = !(fault->slot->flags & KVM_MEM_READONLY);
fault->max_level = kvm_max_private_mapping_level(vcpu->kvm, fault->pfn,
fault->max_level, max_order);
return RET_PF_CONTINUE;
}
static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
bool async;
if (fault->is_private)
return kvm_faultin_pfn_private(vcpu, fault);
async = false;
fault->pfn = __gfn_to_pfn_memslot(fault->slot, fault->gfn, false, false,
&async, fault->write,
&fault->map_writable, &fault->hva);
if (!async)
return RET_PF_CONTINUE; /* *pfn has correct page already */
if (!fault->prefetch && kvm_can_do_async_pf(vcpu)) {
trace_kvm_try_async_get_page(fault->addr, fault->gfn);
if (kvm_find_async_pf_gfn(vcpu, fault->gfn)) {
trace_kvm_async_pf_repeated_fault(fault->addr, fault->gfn);
kvm_make_request(KVM_REQ_APF_HALT, vcpu);
return RET_PF_RETRY;
} else if (kvm_arch_setup_async_pf(vcpu, fault)) {
return RET_PF_RETRY;
}
}
/*
* Allow gup to bail on pending non-fatal signals when it's also allowed
* to wait for IO. Note, gup always bails if it is unable to quickly
* get a page and a fatal signal, i.e. SIGKILL, is pending.
*/
fault->pfn = __gfn_to_pfn_memslot(fault->slot, fault->gfn, false, true,
NULL, fault->write,
&fault->map_writable, &fault->hva);
return RET_PF_CONTINUE;
}
static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
unsigned int access)
{
struct kvm_memory_slot *slot = fault->slot;
int ret;
/*
* Note that the mmu_invalidate_seq also serves to detect a concurrent
* change in attributes. is_page_fault_stale() will detect an
* invalidation relate to fault->fn and resume the guest without
* installing a mapping in the page tables.
*/
fault->mmu_seq = vcpu->kvm->mmu_invalidate_seq;
smp_rmb();
/*
* Now that we have a snapshot of mmu_invalidate_seq we can check for a
* private vs. shared mismatch.
*/
if (fault->is_private != kvm_mem_is_private(vcpu->kvm, fault->gfn)) {
kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
return -EFAULT;
}
if (unlikely(!slot))
return kvm_handle_noslot_fault(vcpu, fault, access);
/*
* Retry the page fault if the gfn hit a memslot that is being deleted
* or moved. This ensures any existing SPTEs for the old memslot will
* be zapped before KVM inserts a new MMIO SPTE for the gfn.
*/
if (slot->flags & KVM_MEMSLOT_INVALID)
return RET_PF_RETRY;
if (slot->id == APIC_ACCESS_PAGE_PRIVATE_MEMSLOT) {
/*
* Don't map L1's APIC access page into L2, KVM doesn't support
* using APICv/AVIC to accelerate L2 accesses to L1's APIC,
* i.e. the access needs to be emulated. Emulating access to
* L1's APIC is also correct if L1 is accelerating L2's own
* virtual APIC, but for some reason L1 also maps _L1's_ APIC
* into L2. Note, vcpu_is_mmio_gpa() always treats access to
* the APIC as MMIO. Allow an MMIO SPTE to be created, as KVM
* uses different roots for L1 vs. L2, i.e. there is no danger
* of breaking APICv/AVIC for L1.
*/
if (is_guest_mode(vcpu))
return kvm_handle_noslot_fault(vcpu, fault, access);
/*
* If the APIC access page exists but is disabled, go directly
* to emulation without caching the MMIO access or creating a
* MMIO SPTE. That way the cache doesn't need to be purged
* when the AVIC is re-enabled.
*/
if (!kvm_apicv_activated(vcpu->kvm))
return RET_PF_EMULATE;
}
/*
* Check for a relevant mmu_notifier invalidation event before getting
* the pfn from the primary MMU, and before acquiring mmu_lock.
*
* For mmu_lock, if there is an in-progress invalidation and the kernel
* allows preemption, the invalidation task may drop mmu_lock and yield
* in response to mmu_lock being contended, which is *very* counter-
* productive as this vCPU can't actually make forward progress until
* the invalidation completes.
*
* Retrying now can also avoid unnessary lock contention in the primary
* MMU, as the primary MMU doesn't necessarily hold a single lock for
* the duration of the invalidation, i.e. faulting in a conflicting pfn
* can cause the invalidation to take longer by holding locks that are
* needed to complete the invalidation.
*
* Do the pre-check even for non-preemtible kernels, i.e. even if KVM
* will never yield mmu_lock in response to contention, as this vCPU is
* *guaranteed* to need to retry, i.e. waiting until mmu_lock is held
* to detect retry guarantees the worst case latency for the vCPU.
*/
if (mmu_invalidate_retry_gfn_unsafe(vcpu->kvm, fault->mmu_seq, fault->gfn))
return RET_PF_RETRY;
ret = __kvm_faultin_pfn(vcpu, fault);
if (ret != RET_PF_CONTINUE)
return ret;
if (unlikely(is_error_pfn(fault->pfn)))
return kvm_handle_error_pfn(vcpu, fault);
if (WARN_ON_ONCE(!fault->slot || is_noslot_pfn(fault->pfn)))
return kvm_handle_noslot_fault(vcpu, fault, access);
/*
* Check again for a relevant mmu_notifier invalidation event purely to
* avoid contending mmu_lock. Most invalidations will be detected by
* the previous check, but checking is extremely cheap relative to the
* overall cost of failing to detect the invalidation until after
* mmu_lock is acquired.
*/
if (mmu_invalidate_retry_gfn_unsafe(vcpu->kvm, fault->mmu_seq, fault->gfn)) {
kvm_release_pfn_clean(fault->pfn);
return RET_PF_RETRY;
}
return RET_PF_CONTINUE;
}
/*
* Returns true if the page fault is stale and needs to be retried, i.e. if the
* root was invalidated by a memslot update or a relevant mmu_notifier fired.
*/
static bool is_page_fault_stale(struct kvm_vcpu *vcpu,
struct kvm_page_fault *fault)
{
struct kvm_mmu_page *sp = root_to_sp(vcpu->arch.mmu->root.hpa);
/* Special roots, e.g. pae_root, are not backed by shadow pages. */
if (sp && is_obsolete_sp(vcpu->kvm, sp))
return true;
/*
* Roots without an associated shadow page are considered invalid if
* there is a pending request to free obsolete roots. The request is
* only a hint that the current root _may_ be obsolete and needs to be
* reloaded, e.g. if the guest frees a PGD that KVM is tracking as a
* previous root, then __kvm_mmu_prepare_zap_page() signals all vCPUs
* to reload even if no vCPU is actively using the root.
*/
if (!sp && kvm_test_request(KVM_REQ_MMU_FREE_OBSOLETE_ROOTS, vcpu))
return true;
/*
* Check for a relevant mmu_notifier invalidation event one last time
* now that mmu_lock is held, as the "unsafe" checks performed without
* holding mmu_lock can get false negatives.
*/
return fault->slot &&
mmu_invalidate_retry_gfn(vcpu->kvm, fault->mmu_seq, fault->gfn);
}
static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
int r;
/* Dummy roots are used only for shadowing bad guest roots. */
if (WARN_ON_ONCE(kvm_mmu_is_dummy_root(vcpu->arch.mmu->root.hpa)))
return RET_PF_RETRY;
if (page_fault_handle_page_track(vcpu, fault))
return RET_PF_WRITE_PROTECTED;
r = fast_page_fault(vcpu, fault);
if (r != RET_PF_INVALID)
return r;
r = mmu_topup_memory_caches(vcpu, false);
if (r)
return r;
r = kvm_faultin_pfn(vcpu, fault, ACC_ALL);
if (r != RET_PF_CONTINUE)
return r;
r = RET_PF_RETRY;
write_lock(&vcpu->kvm->mmu_lock);
if (is_page_fault_stale(vcpu, fault))
goto out_unlock;
r = make_mmu_pages_available(vcpu);
if (r)
goto out_unlock;
r = direct_map(vcpu, fault);
out_unlock:
write_unlock(&vcpu->kvm->mmu_lock);
kvm_release_pfn_clean(fault->pfn);
return r;
}
static int nonpaging_page_fault(struct kvm_vcpu *vcpu,
struct kvm_page_fault *fault)
{
/* This path builds a PAE pagetable, we can map 2mb pages at maximum. */
fault->max_level = PG_LEVEL_2M;
return direct_page_fault(vcpu, fault);
}
int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
u64 fault_address, char *insn, int insn_len)
{
int r = 1;
u32 flags = vcpu->arch.apf.host_apf_flags;
#ifndef CONFIG_X86_64
/* A 64-bit CR2 should be impossible on 32-bit KVM. */
if (WARN_ON_ONCE(fault_address >> 32))
return -EFAULT;
#endif
/*
* Legacy #PF exception only have a 32-bit error code. Simply drop the
* upper bits as KVM doesn't use them for #PF (because they are never
* set), and to ensure there are no collisions with KVM-defined bits.
*/
if (WARN_ON_ONCE(error_code >> 32))
error_code = lower_32_bits(error_code);
/*
* Restrict KVM-defined flags to bits 63:32 so that it's impossible for
* them to conflict with #PF error codes, which are limited to 32 bits.
*/
BUILD_BUG_ON(lower_32_bits(PFERR_SYNTHETIC_MASK));
vcpu->arch.l1tf_flush_l1d = true;
if (!flags) {
trace_kvm_page_fault(vcpu, fault_address, error_code);
r = kvm_mmu_page_fault(vcpu, fault_address, error_code, insn,
insn_len);
} else if (flags & KVM_PV_REASON_PAGE_NOT_PRESENT) {
vcpu->arch.apf.host_apf_flags = 0;
local_irq_disable();
kvm_async_pf_task_wait_schedule(fault_address);
local_irq_enable();
} else {
WARN_ONCE(1, "Unexpected host async PF flags: %x\n", flags);
}
return r;
}
EXPORT_SYMBOL_GPL(kvm_handle_page_fault);
#ifdef CONFIG_X86_64
static int kvm_tdp_mmu_page_fault(struct kvm_vcpu *vcpu,
struct kvm_page_fault *fault)
{
int r;
if (page_fault_handle_page_track(vcpu, fault))
return RET_PF_WRITE_PROTECTED;
r = fast_page_fault(vcpu, fault);
if (r != RET_PF_INVALID)
return r;
r = mmu_topup_memory_caches(vcpu, false);
if (r)
return r;
r = kvm_faultin_pfn(vcpu, fault, ACC_ALL);
if (r != RET_PF_CONTINUE)
return r;
r = RET_PF_RETRY;
read_lock(&vcpu->kvm->mmu_lock);
if (is_page_fault_stale(vcpu, fault))
goto out_unlock;
r = kvm_tdp_mmu_map(vcpu, fault);
out_unlock:
read_unlock(&vcpu->kvm->mmu_lock);
kvm_release_pfn_clean(fault->pfn);
return r;
}
#endif
bool kvm_mmu_may_ignore_guest_pat(void)
{
/*
* When EPT is enabled (shadow_memtype_mask is non-zero), and the VM
* has non-coherent DMA (DMA doesn't snoop CPU caches), KVM's ABI is to
* honor the memtype from the guest's PAT so that guest accesses to
* memory that is DMA'd aren't cached against the guest's wishes. As a
* result, KVM _may_ ignore guest PAT, whereas without non-coherent DMA,
* KVM _always_ ignores guest PAT (when EPT is enabled).
*/
return shadow_memtype_mask;
}
int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
#ifdef CONFIG_X86_64
if (tdp_mmu_enabled)
return kvm_tdp_mmu_page_fault(vcpu, fault);
#endif
return direct_page_fault(vcpu, fault);
}
static int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code,
u8 *level)
{
int r;
/*
* Restrict to TDP page fault, since that's the only case where the MMU
* is indexed by GPA.
*/
if (vcpu->arch.mmu->page_fault != kvm_tdp_page_fault)
return -EOPNOTSUPP;
do {
if (signal_pending(current))
return -EINTR;
cond_resched();
r = kvm_mmu_do_page_fault(vcpu, gpa, error_code, true, NULL, level);
} while (r == RET_PF_RETRY);
if (r < 0)
return r;
switch (r) {
case RET_PF_FIXED:
case RET_PF_SPURIOUS:
case RET_PF_WRITE_PROTECTED:
return 0;
case RET_PF_EMULATE:
return -ENOENT;
case RET_PF_RETRY:
case RET_PF_CONTINUE:
case RET_PF_INVALID:
default:
WARN_ONCE(1, "could not fix page fault during prefault");
return -EIO;
}
}
long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu,
struct kvm_pre_fault_memory *range)
{
u64 error_code = PFERR_GUEST_FINAL_MASK;
u8 level = PG_LEVEL_4K;
u64 end;
int r;
if (!vcpu->kvm->arch.pre_fault_allowed)
return -EOPNOTSUPP;
/*
* reload is efficient when called repeatedly, so we can do it on
* every iteration.
*/
r = kvm_mmu_reload(vcpu);
if (r)
return r;
if (kvm_arch_has_private_mem(vcpu->kvm) &&
kvm_mem_is_private(vcpu->kvm, gpa_to_gfn(range->gpa)))
error_code |= PFERR_PRIVATE_ACCESS;
/*
* Shadow paging uses GVA for kvm page fault, so restrict to
* two-dimensional paging.
*/
r = kvm_tdp_map_page(vcpu, range->gpa, error_code, &level);
if (r < 0)
return r;
/*
* If the mapping that covers range->gpa can use a huge page, it
* may start below it or end after range->gpa + range->size.
*/
end = (range->gpa & KVM_HPAGE_MASK(level)) + KVM_HPAGE_SIZE(level);
return min(range->size, end - range->gpa);
}
static void nonpaging_init_context(struct kvm_mmu *context)
{
context->page_fault = nonpaging_page_fault;
context->gva_to_gpa = nonpaging_gva_to_gpa;
context->sync_spte = NULL;
}
static inline bool is_root_usable(struct kvm_mmu_root_info *root, gpa_t pgd,
union kvm_mmu_page_role role)
{
struct kvm_mmu_page *sp;
if (!VALID_PAGE(root->hpa))
return false;
if (!role.direct && pgd != root->pgd)
return false;
sp = root_to_sp(root->hpa);
if (WARN_ON_ONCE(!sp))
return false;
return role.word == sp->role.word;
}
/*
* Find out if a previously cached root matching the new pgd/role is available,
* and insert the current root as the MRU in the cache.
* If a matching root is found, it is assigned to kvm_mmu->root and
* true is returned.
* If no match is found, kvm_mmu->root is left invalid, the LRU root is
* evicted to make room for the current root, and false is returned.
*/
static bool cached_root_find_and_keep_current(struct kvm *kvm, struct kvm_mmu *mmu,
gpa_t new_pgd,
union kvm_mmu_page_role new_role)
{
uint i;
if (is_root_usable(&mmu->root, new_pgd, new_role))
return true;
for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) {
/*
* The swaps end up rotating the cache like this:
* C 0 1 2 3 (on entry to the function)
* 0 C 1 2 3
* 1 C 0 2 3
* 2 C 0 1 3
* 3 C 0 1 2 (on exit from the loop)
*/
swap(mmu->root, mmu->prev_roots[i]);
if (is_root_usable(&mmu->root, new_pgd, new_role))
return true;
}
kvm_mmu_free_roots(kvm, mmu, KVM_MMU_ROOT_CURRENT);
return false;
}
/*
* Find out if a previously cached root matching the new pgd/role is available.
* On entry, mmu->root is invalid.
* If a matching root is found, it is assigned to kvm_mmu->root, the LRU entry
* of the cache becomes invalid, and true is returned.
* If no match is found, kvm_mmu->root is left invalid and false is returned.
*/
static bool cached_root_find_without_current(struct kvm *kvm, struct kvm_mmu *mmu,
gpa_t new_pgd,
union kvm_mmu_page_role new_role)
{
uint i;
for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
if (is_root_usable(&mmu->prev_roots[i], new_pgd, new_role))
goto hit;
return false;
hit:
swap(mmu->root, mmu->prev_roots[i]);
/* Bubble up the remaining roots. */
for (; i < KVM_MMU_NUM_PREV_ROOTS - 1; i++)
mmu->prev_roots[i] = mmu->prev_roots[i + 1];
mmu->prev_roots[i].hpa = INVALID_PAGE;
return true;
}
static bool fast_pgd_switch(struct kvm *kvm, struct kvm_mmu *mmu,
gpa_t new_pgd, union kvm_mmu_page_role new_role)
{
/*
* Limit reuse to 64-bit hosts+VMs without "special" roots in order to
* avoid having to deal with PDPTEs and other complexities.
*/
if (VALID_PAGE(mmu->root.hpa) && !root_to_sp(mmu->root.hpa))
kvm_mmu_free_roots(kvm, mmu, KVM_MMU_ROOT_CURRENT);
if (VALID_PAGE(mmu->root.hpa))
return cached_root_find_and_keep_current(kvm, mmu, new_pgd, new_role);
else
return cached_root_find_without_current(kvm, mmu, new_pgd, new_role);
}
void kvm_mmu_new_pgd(struct kvm_vcpu *vcpu, gpa_t new_pgd)
{
struct kvm_mmu *mmu = vcpu->arch.mmu;
union kvm_mmu_page_role new_role = mmu->root_role;
/*
* Return immediately if no usable root was found, kvm_mmu_reload()
* will establish a valid root prior to the next VM-Enter.
*/
if (!fast_pgd_switch(vcpu->kvm, mmu, new_pgd, new_role))
return;
/*
* It's possible that the cached previous root page is obsolete because
* of a change in the MMU generation number. However, changing the
* generation number is accompanied by KVM_REQ_MMU_FREE_OBSOLETE_ROOTS,
* which will free the root set here and allocate a new one.
*/
kvm_make_request(KVM_REQ_LOAD_MMU_PGD, vcpu);
if (force_flush_and_sync_on_reuse) {
kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);
kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu);
}
/*
* The last MMIO access's GVA and GPA are cached in the VCPU. When
* switching to a new CR3, that GVA->GPA mapping may no longer be
* valid. So clear any cached MMIO info even when we don't need to sync
* the shadow page tables.
*/
vcpu_clear_mmio_info(vcpu, MMIO_GVA_ANY);
/*
* If this is a direct root page, it doesn't have a write flooding
* count. Otherwise, clear the write flooding count.
*/
if (!new_role.direct) {
struct kvm_mmu_page *sp = root_to_sp(vcpu->arch.mmu->root.hpa);
if (!WARN_ON_ONCE(!sp))
__clear_sp_write_flooding_count(sp);
}
}
EXPORT_SYMBOL_GPL(kvm_mmu_new_pgd);
static bool sync_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, gfn_t gfn,
unsigned int access)
{
if (unlikely(is_mmio_spte(vcpu->kvm, *sptep))) {
if (gfn != get_mmio_spte_gfn(*sptep)) {
mmu_spte_clear_no_track(sptep);
return true;
}
mark_mmio_spte(vcpu, sptep, gfn, access);
return true;
}
return false;
}
#define PTTYPE_EPT 18 /* arbitrary */
#define PTTYPE PTTYPE_EPT
#include "paging_tmpl.h"
#undef PTTYPE
#define PTTYPE 64
#include "paging_tmpl.h"
#undef PTTYPE
#define PTTYPE 32
#include "paging_tmpl.h"
#undef PTTYPE
static void __reset_rsvds_bits_mask(struct rsvd_bits_validate *rsvd_check,
u64 pa_bits_rsvd, int level, bool nx,
bool gbpages, bool pse, bool amd)
{
u64 gbpages_bit_rsvd = 0;
u64 nonleaf_bit8_rsvd = 0;
u64 high_bits_rsvd;
rsvd_check->bad_mt_xwr = 0;
if (!gbpages)
gbpages_bit_rsvd = rsvd_bits(7, 7);
if (level == PT32E_ROOT_LEVEL)
high_bits_rsvd = pa_bits_rsvd & rsvd_bits(0, 62);
else
high_bits_rsvd = pa_bits_rsvd & rsvd_bits(0, 51);
/* Note, NX doesn't exist in PDPTEs, this is handled below. */
if (!nx)
high_bits_rsvd |= rsvd_bits(63, 63);
/*
* Non-leaf PML4Es and PDPEs reserve bit 8 (which would be the G bit for
* leaf entries) on AMD CPUs only.
*/
if (amd)
nonleaf_bit8_rsvd = rsvd_bits(8, 8);
switch (level) {
case PT32_ROOT_LEVEL:
/* no rsvd bits for 2 level 4K page table entries */
rsvd_check->rsvd_bits_mask[0][1] = 0;
rsvd_check->rsvd_bits_mask[0][0] = 0;
rsvd_check->rsvd_bits_mask[1][0] =
rsvd_check->rsvd_bits_mask[0][0];
if (!pse) {
rsvd_check->rsvd_bits_mask[1][1] = 0;
break;
}
if (is_cpuid_PSE36())
/* 36bits PSE 4MB page */
rsvd_check->rsvd_bits_mask[1][1] = rsvd_bits(17, 21);
else
/* 32 bits PSE 4MB page */
rsvd_check->rsvd_bits_mask[1][1] = rsvd_bits(13, 21);
break;
case PT32E_ROOT_LEVEL:
rsvd_check->rsvd_bits_mask[0][2] = rsvd_bits(63, 63) |
high_bits_rsvd |
rsvd_bits(5, 8) |
rsvd_bits(1, 2); /* PDPTE */
rsvd_check->rsvd_bits_mask[0][1] = high_bits_rsvd; /* PDE */
rsvd_check->rsvd_bits_mask[0][0] = high_bits_rsvd; /* PTE */
rsvd_check->rsvd_bits_mask[1][1] = high_bits_rsvd |
rsvd_bits(13, 20); /* large page */
rsvd_check->rsvd_bits_mask[1][0] =
rsvd_check->rsvd_bits_mask[0][0];
break;
case PT64_ROOT_5LEVEL:
rsvd_check->rsvd_bits_mask[0][4] = high_bits_rsvd |
nonleaf_bit8_rsvd |
rsvd_bits(7, 7);
rsvd_check->rsvd_bits_mask[1][4] =
rsvd_check->rsvd_bits_mask[0][4];
fallthrough;
case PT64_ROOT_4LEVEL:
rsvd_check->rsvd_bits_mask[0][3] = high_bits_rsvd |
nonleaf_bit8_rsvd |
rsvd_bits(7, 7);
rsvd_check->rsvd_bits_mask[0][2] = high_bits_rsvd |
gbpages_bit_rsvd;
rsvd_check->rsvd_bits_mask[0][1] = high_bits_rsvd;
rsvd_check->rsvd_bits_mask[0][0] = high_bits_rsvd;
rsvd_check->rsvd_bits_mask[1][3] =
rsvd_check->rsvd_bits_mask[0][3];
rsvd_check->rsvd_bits_mask[1][2] = high_bits_rsvd |
gbpages_bit_rsvd |
rsvd_bits(13, 29);
rsvd_check->rsvd_bits_mask[1][1] = high_bits_rsvd |
rsvd_bits(13, 20); /* large page */
rsvd_check->rsvd_bits_mask[1][0] =
rsvd_check->rsvd_bits_mask[0][0];
break;
}
}
static void reset_guest_rsvds_bits_mask(struct kvm_vcpu *vcpu,
struct kvm_mmu *context)
{
__reset_rsvds_bits_mask(&context->guest_rsvd_check,
vcpu->arch.reserved_gpa_bits,
context->cpu_role.base.level, is_efer_nx(context),
guest_can_use(vcpu, X86_FEATURE_GBPAGES),
is_cr4_pse(context),
guest_cpuid_is_amd_compatible(vcpu));
}
static void __reset_rsvds_bits_mask_ept(struct rsvd_bits_validate *rsvd_check,
u64 pa_bits_rsvd, bool execonly,
int huge_page_level)
{
u64 high_bits_rsvd = pa_bits_rsvd & rsvd_bits(0, 51);
u64 large_1g_rsvd = 0, large_2m_rsvd = 0;
u64 bad_mt_xwr;
if (huge_page_level < PG_LEVEL_1G)
large_1g_rsvd = rsvd_bits(7, 7);
if (huge_page_level < PG_LEVEL_2M)
large_2m_rsvd = rsvd_bits(7, 7);
rsvd_check->rsvd_bits_mask[0][4] = high_bits_rsvd | rsvd_bits(3, 7);
rsvd_check->rsvd_bits_mask[0][3] = high_bits_rsvd | rsvd_bits(3, 7);
rsvd_check->rsvd_bits_mask[0][2] = high_bits_rsvd | rsvd_bits(3, 6) | large_1g_rsvd;
rsvd_check->rsvd_bits_mask[0][1] = high_bits_rsvd | rsvd_bits(3, 6) | large_2m_rsvd;
rsvd_check->rsvd_bits_mask[0][0] = high_bits_rsvd;
/* large page */
rsvd_check->rsvd_bits_mask[1][4] = rsvd_check->rsvd_bits_mask[0][4];
rsvd_check->rsvd_bits_mask[1][3] = rsvd_check->rsvd_bits_mask[0][3];
rsvd_check->rsvd_bits_mask[1][2] = high_bits_rsvd | rsvd_bits(12, 29) | large_1g_rsvd;
rsvd_check->rsvd_bits_mask[1][1] = high_bits_rsvd | rsvd_bits(12, 20) | large_2m_rsvd;
rsvd_check->rsvd_bits_mask[1][0] = rsvd_check->rsvd_bits_mask[0][0];
bad_mt_xwr = 0xFFull << (2 * 8); /* bits 3..5 must not be 2 */
bad_mt_xwr |= 0xFFull << (3 * 8); /* bits 3..5 must not be 3 */
bad_mt_xwr |= 0xFFull << (7 * 8); /* bits 3..5 must not be 7 */
bad_mt_xwr |= REPEAT_BYTE(1ull << 2); /* bits 0..2 must not be 010 */
bad_mt_xwr |= REPEAT_BYTE(1ull << 6); /* bits 0..2 must not be 110 */
if (!execonly) {
/* bits 0..2 must not be 100 unless VMX capabilities allow it */
bad_mt_xwr |= REPEAT_BYTE(1ull << 4);
}
rsvd_check->bad_mt_xwr = bad_mt_xwr;
}
static void reset_rsvds_bits_mask_ept(struct kvm_vcpu *vcpu,
struct kvm_mmu *context, bool execonly, int huge_page_level)
{
__reset_rsvds_bits_mask_ept(&context->guest_rsvd_check,
vcpu->arch.reserved_gpa_bits, execonly,
huge_page_level);
}
static inline u64 reserved_hpa_bits(void)
{
return rsvd_bits(kvm_host.maxphyaddr, 63);
}
/*
* the page table on host is the shadow page table for the page
* table in guest or amd nested guest, its mmu features completely
* follow the features in guest.
*/
static void reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu,
struct kvm_mmu *context)
{
/* @amd adds a check on bit of SPTEs, which KVM shouldn't use anyways. */
bool is_amd = true;
/* KVM doesn't use 2-level page tables for the shadow MMU. */
bool is_pse = false;
struct rsvd_bits_validate *shadow_zero_check;
int i;
WARN_ON_ONCE(context->root_role.level < PT32E_ROOT_LEVEL);
shadow_zero_check = &context->shadow_zero_check;
__reset_rsvds_bits_mask(shadow_zero_check, reserved_hpa_bits(),
context->root_role.level,
context->root_role.efer_nx,
guest_can_use(vcpu, X86_FEATURE_GBPAGES),
is_pse, is_amd);
if (!shadow_me_mask)
return;
for (i = context->root_role.level; --i >= 0;) {
/*
* So far shadow_me_value is a constant during KVM's life
* time. Bits in shadow_me_value are allowed to be set.
* Bits in shadow_me_mask but not in shadow_me_value are
* not allowed to be set.
*/
shadow_zero_check->rsvd_bits_mask[0][i] |= shadow_me_mask;
shadow_zero_check->rsvd_bits_mask[1][i] |= shadow_me_mask;
shadow_zero_check->rsvd_bits_mask[0][i] &= ~shadow_me_value;
shadow_zero_check->rsvd_bits_mask[1][i] &= ~shadow_me_value;
}
}
static inline bool boot_cpu_is_amd(void)
{
WARN_ON_ONCE(!tdp_enabled);
return shadow_x_mask == 0;
}
/*
* the direct page table on host, use as much mmu features as
* possible, however, kvm currently does not do execution-protection.
*/
static void reset_tdp_shadow_zero_bits_mask(struct kvm_mmu *context)
{
struct rsvd_bits_validate *shadow_zero_check;
int i;
shadow_zero_check = &context->shadow_zero_check;
if (boot_cpu_is_amd())
__reset_rsvds_bits_mask(shadow_zero_check, reserved_hpa_bits(),
context->root_role.level, true,
boot_cpu_has(X86_FEATURE_GBPAGES),
false, true);
else
__reset_rsvds_bits_mask_ept(shadow_zero_check,
reserved_hpa_bits(), false,
max_huge_page_level);
if (!shadow_me_mask)
return;
for (i = context->root_role.level; --i >= 0;) {
shadow_zero_check->rsvd_bits_mask[0][i] &= ~shadow_me_mask;
shadow_zero_check->rsvd_bits_mask[1][i] &= ~shadow_me_mask;
}
}
/*
* as the comments in reset_shadow_zero_bits_mask() except it
* is the shadow page table for intel nested guest.
*/
static void
reset_ept_shadow_zero_bits_mask(struct kvm_mmu *context, bool execonly)
{
__reset_rsvds_bits_mask_ept(&context->shadow_zero_check,
reserved_hpa_bits(), execonly,
max_huge_page_level);
}
#define BYTE_MASK(access) \
((1 & (access) ? 2 : 0) | \
(2 & (access) ? 4 : 0) | \
(3 & (access) ? 8 : 0) | \
(4 & (access) ? 16 : 0) | \
(5 & (access) ? 32 : 0) | \
(6 & (access) ? 64 : 0) | \
(7 & (access) ? 128 : 0))
static void update_permission_bitmask(struct kvm_mmu *mmu, bool ept)
{
unsigned byte;
const u8 x = BYTE_MASK(ACC_EXEC_MASK);
const u8 w = BYTE_MASK(ACC_WRITE_MASK);
const u8 u = BYTE_MASK(ACC_USER_MASK);
bool cr4_smep = is_cr4_smep(mmu);
bool cr4_smap = is_cr4_smap(mmu);
bool cr0_wp = is_cr0_wp(mmu);
bool efer_nx = is_efer_nx(mmu);
for (byte = 0; byte < ARRAY_SIZE(mmu->permissions); ++byte) {
unsigned pfec = byte << 1;
/*
* Each "*f" variable has a 1 bit for each UWX value
* that causes a fault with the given PFEC.
*/
/* Faults from writes to non-writable pages */
u8 wf = (pfec & PFERR_WRITE_MASK) ? (u8)~w : 0;
/* Faults from user mode accesses to supervisor pages */
u8 uf = (pfec & PFERR_USER_MASK) ? (u8)~u : 0;
/* Faults from fetches of non-executable pages*/
u8 ff = (pfec & PFERR_FETCH_MASK) ? (u8)~x : 0;
/* Faults from kernel mode fetches of user pages */
u8 smepf = 0;
/* Faults from kernel mode accesses of user pages */
u8 smapf = 0;
if (!ept) {
/* Faults from kernel mode accesses to user pages */
u8 kf = (pfec & PFERR_USER_MASK) ? 0 : u;
/* Not really needed: !nx will cause pte.nx to fault */
if (!efer_nx)
ff = 0;
/* Allow supervisor writes if !cr0.wp */
if (!cr0_wp)
wf = (pfec & PFERR_USER_MASK) ? wf : 0;
/* Disallow supervisor fetches of user code if cr4.smep */
if (cr4_smep)
smepf = (pfec & PFERR_FETCH_MASK) ? kf : 0;
/*
* SMAP:kernel-mode data accesses from user-mode
* mappings should fault. A fault is considered
* as a SMAP violation if all of the following
* conditions are true:
* - X86_CR4_SMAP is set in CR4
* - A user page is accessed
* - The access is not a fetch
* - The access is supervisor mode
* - If implicit supervisor access or X86_EFLAGS_AC is clear
*
* Here, we cover the first four conditions.
* The fifth is computed dynamically in permission_fault();
* PFERR_RSVD_MASK bit will be set in PFEC if the access is
* *not* subject to SMAP restrictions.
*/
if (cr4_smap)
smapf = (pfec & (PFERR_RSVD_MASK|PFERR_FETCH_MASK)) ? 0 : kf;
}
mmu->permissions[byte] = ff | uf | wf | smepf | smapf;
}
}
/*
* PKU is an additional mechanism by which the paging controls access to
* user-mode addresses based on the value in the PKRU register. Protection
* key violations are reported through a bit in the page fault error code.
* Unlike other bits of the error code, the PK bit is not known at the
* call site of e.g. gva_to_gpa; it must be computed directly in
* permission_fault based on two bits of PKRU, on some machine state (CR4,
* CR0, EFER, CPL), and on other bits of the error code and the page tables.
*
* In particular the following conditions come from the error code, the
* page tables and the machine state:
* - PK is always zero unless CR4.PKE=1 and EFER.LMA=1
* - PK is always zero if RSVD=1 (reserved bit set) or F=1 (instruction fetch)
* - PK is always zero if U=0 in the page tables
* - PKRU.WD is ignored if CR0.WP=0 and the access is a supervisor access.
*
* The PKRU bitmask caches the result of these four conditions. The error
* code (minus the P bit) and the page table's U bit form an index into the
* PKRU bitmask. Two bits of the PKRU bitmask are then extracted and ANDed
* with the two bits of the PKRU register corresponding to the protection key.
* For the first three conditions above the bits will be 00, thus masking
* away both AD and WD. For all reads or if the last condition holds, WD
* only will be masked away.
*/
static void update_pkru_bitmask(struct kvm_mmu *mmu)
{
unsigned bit;
bool wp;
mmu->pkru_mask = 0;
if (!is_cr4_pke(mmu))
return;
wp = is_cr0_wp(mmu);
for (bit = 0; bit < ARRAY_SIZE(mmu->permissions); ++bit) {
unsigned pfec, pkey_bits;
bool check_pkey, check_write, ff, uf, wf, pte_user;
pfec = bit << 1;
ff = pfec & PFERR_FETCH_MASK;
uf = pfec & PFERR_USER_MASK;
wf = pfec & PFERR_WRITE_MASK;
/* PFEC.RSVD is replaced by ACC_USER_MASK. */
pte_user = pfec & PFERR_RSVD_MASK;
/*
* Only need to check the access which is not an
* instruction fetch and is to a user page.
*/
check_pkey = (!ff && pte_user);
/*
* write access is controlled by PKRU if it is a
* user access or CR0.WP = 1.
*/
check_write = check_pkey && wf && (uf || wp);
/* PKRU.AD stops both read and write access. */
pkey_bits = !!check_pkey;
/* PKRU.WD stops write access. */
pkey_bits |= (!!check_write) << 1;
mmu->pkru_mask |= (pkey_bits & 3) << pfec;
}
}
static void reset_guest_paging_metadata(struct kvm_vcpu *vcpu,
struct kvm_mmu *mmu)
{
if (!is_cr0_pg(mmu))
return;
reset_guest_rsvds_bits_mask(vcpu, mmu);
update_permission_bitmask(mmu, false);
update_pkru_bitmask(mmu);
}
static void paging64_init_context(struct kvm_mmu *context)
{
context->page_fault = paging64_page_fault;
context->gva_to_gpa = paging64_gva_to_gpa;
context->sync_spte = paging64_sync_spte;
}
static void paging32_init_context(struct kvm_mmu *context)
{
context->page_fault = paging32_page_fault;
context->gva_to_gpa = paging32_gva_to_gpa;
context->sync_spte = paging32_sync_spte;
}
static union kvm_cpu_role kvm_calc_cpu_role(struct kvm_vcpu *vcpu,
const struct kvm_mmu_role_regs *regs)
{
union kvm_cpu_role role = {0};
role.base.access = ACC_ALL;
role.base.smm = is_smm(vcpu);
role.base.guest_mode = is_guest_mode(vcpu);
role.ext.valid = 1;
if (!____is_cr0_pg(regs)) {
role.base.direct = 1;
return role;
}
role.base.efer_nx = ____is_efer_nx(regs);
role.base.cr0_wp = ____is_cr0_wp(regs);
role.base.smep_andnot_wp = ____is_cr4_smep(regs) && !____is_cr0_wp(regs);
role.base.smap_andnot_wp = ____is_cr4_smap(regs) && !____is_cr0_wp(regs);
role.base.has_4_byte_gpte = !____is_cr4_pae(regs);
if (____is_efer_lma(regs))
role.base.level = ____is_cr4_la57(regs) ? PT64_ROOT_5LEVEL
: PT64_ROOT_4LEVEL;
else if (____is_cr4_pae(regs))
role.base.level = PT32E_ROOT_LEVEL;
else
role.base.level = PT32_ROOT_LEVEL;
role.ext.cr4_smep = ____is_cr4_smep(regs);
role.ext.cr4_smap = ____is_cr4_smap(regs);
role.ext.cr4_pse = ____is_cr4_pse(regs);
/* PKEY and LA57 are active iff long mode is active. */
role.ext.cr4_pke = ____is_efer_lma(regs) && ____is_cr4_pke(regs);
role.ext.cr4_la57 = ____is_efer_lma(regs) && ____is_cr4_la57(regs);
role.ext.efer_lma = ____is_efer_lma(regs);
return role;
}
void __kvm_mmu_refresh_passthrough_bits(struct kvm_vcpu *vcpu,
struct kvm_mmu *mmu)
{
const bool cr0_wp = kvm_is_cr0_bit_set(vcpu, X86_CR0_WP);
BUILD_BUG_ON((KVM_MMU_CR0_ROLE_BITS & KVM_POSSIBLE_CR0_GUEST_BITS) != X86_CR0_WP);
BUILD_BUG_ON((KVM_MMU_CR4_ROLE_BITS & KVM_POSSIBLE_CR4_GUEST_BITS));
if (is_cr0_wp(mmu) == cr0_wp)
return;
mmu->cpu_role.base.cr0_wp = cr0_wp;
reset_guest_paging_metadata(vcpu, mmu);
}
static inline int kvm_mmu_get_tdp_level(struct kvm_vcpu *vcpu)
{
/* tdp_root_level is architecture forced level, use it if nonzero */
if (tdp_root_level)
return tdp_root_level;
/* Use 5-level TDP if and only if it's useful/necessary. */
if (max_tdp_level == 5 && cpuid_maxphyaddr(vcpu) <= 48)
return 4;
return max_tdp_level;
}
u8 kvm_mmu_get_max_tdp_level(void)
{
return tdp_root_level ? tdp_root_level : max_tdp_level;
}
static union kvm_mmu_page_role
kvm_calc_tdp_mmu_root_page_role(struct kvm_vcpu *vcpu,
union kvm_cpu_role cpu_role)
{
union kvm_mmu_page_role role = {0};
role.access = ACC_ALL;
role.cr0_wp = true;
role.efer_nx = true;
role.smm = cpu_role.base.smm;
role.guest_mode = cpu_role.base.guest_mode;
role.ad_disabled = !kvm_ad_enabled();
role.level = kvm_mmu_get_tdp_level(vcpu);
role.direct = true;
role.has_4_byte_gpte = false;
return role;
}
static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu,
union kvm_cpu_role cpu_role)
{
struct kvm_mmu *context = &vcpu->arch.root_mmu;
union kvm_mmu_page_role root_role = kvm_calc_tdp_mmu_root_page_role(vcpu, cpu_role);
if (cpu_role.as_u64 == context->cpu_role.as_u64 &&
root_role.word == context->root_role.word)
return;
context->cpu_role.as_u64 = cpu_role.as_u64;
context->root_role.word = root_role.word;
context->page_fault = kvm_tdp_page_fault;
context->sync_spte = NULL;
context->get_guest_pgd = get_guest_cr3;
context->get_pdptr = kvm_pdptr_read;
context->inject_page_fault = kvm_inject_page_fault;
if (!is_cr0_pg(context))
context->gva_to_gpa = nonpaging_gva_to_gpa;
else if (is_cr4_pae(context))
context->gva_to_gpa = paging64_gva_to_gpa;
else
context->gva_to_gpa = paging32_gva_to_gpa;
reset_guest_paging_metadata(vcpu, context);
reset_tdp_shadow_zero_bits_mask(context);
}
static void shadow_mmu_init_context(struct kvm_vcpu *vcpu, struct kvm_mmu *context,
union kvm_cpu_role cpu_role,
union kvm_mmu_page_role root_role)
{
if (cpu_role.as_u64 == context->cpu_role.as_u64 &&
root_role.word == context->root_role.word)
return;
context->cpu_role.as_u64 = cpu_role.as_u64;
context->root_role.word = root_role.word;
if (!is_cr0_pg(context))
nonpaging_init_context(context);
else if (is_cr4_pae(context))
paging64_init_context(context);
else
paging32_init_context(context);
reset_guest_paging_metadata(vcpu, context);
reset_shadow_zero_bits_mask(vcpu, context);
}
static void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu,
union kvm_cpu_role cpu_role)
{
struct kvm_mmu *context = &vcpu->arch.root_mmu;
union kvm_mmu_page_role root_role;
root_role = cpu_role.base;
/* KVM uses PAE paging whenever the guest isn't using 64-bit paging. */
root_role.level = max_t(u32, root_role.level, PT32E_ROOT_LEVEL);
/*
* KVM forces EFER.NX=1 when TDP is disabled, reflect it in the MMU role.
* KVM uses NX when TDP is disabled to handle a variety of scenarios,
* notably for huge SPTEs if iTLB multi-hit mitigation is enabled and
* to generate correct permissions for CR0.WP=0/CR4.SMEP=1/EFER.NX=0.
* The iTLB multi-hit workaround can be toggled at any time, so assume
* NX can be used by any non-nested shadow MMU to avoid having to reset
* MMU contexts.
*/
root_role.efer_nx = true;
shadow_mmu_init_context(vcpu, context, cpu_role, root_role);
}
void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, unsigned long cr0,
unsigned long cr4, u64 efer, gpa_t nested_cr3)
{
struct kvm_mmu *context = &vcpu->arch.guest_mmu;
struct kvm_mmu_role_regs regs = {
.cr0 = cr0,
.cr4 = cr4 & ~X86_CR4_PKE,
.efer = efer,
};
union kvm_cpu_role cpu_role = kvm_calc_cpu_role(vcpu, &regs);
union kvm_mmu_page_role root_role;
/* NPT requires CR0.PG=1. */
WARN_ON_ONCE(cpu_role.base.direct);
root_role = cpu_role.base;
root_role.level = kvm_mmu_get_tdp_level(vcpu);
if (root_role.level == PT64_ROOT_5LEVEL &&
cpu_role.base.level == PT64_ROOT_4LEVEL)
root_role.passthrough = 1;
shadow_mmu_init_context(vcpu, context, cpu_role, root_role);
kvm_mmu_new_pgd(vcpu, nested_cr3);
}
EXPORT_SYMBOL_GPL(kvm_init_shadow_npt_mmu);
static union kvm_cpu_role
kvm_calc_shadow_ept_root_page_role(struct kvm_vcpu *vcpu, bool accessed_dirty,
bool execonly, u8 level)
{
union kvm_cpu_role role = {0};
/*
* KVM does not support SMM transfer monitors, and consequently does not
* support the "entry to SMM" control either. role.base.smm is always 0.
*/
WARN_ON_ONCE(is_smm(vcpu));
role.base.level = level;
role.base.has_4_byte_gpte = false;
role.base.direct = false;
role.base.ad_disabled = !accessed_dirty;
role.base.guest_mode = true;
role.base.access = ACC_ALL;
role.ext.word = 0;
role.ext.execonly = execonly;
role.ext.valid = 1;
return role;
}
void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
int huge_page_level, bool accessed_dirty,
gpa_t new_eptp)
{
struct kvm_mmu *context = &vcpu->arch.guest_mmu;
u8 level = vmx_eptp_page_walk_level(new_eptp);
union kvm_cpu_role new_mode =
kvm_calc_shadow_ept_root_page_role(vcpu, accessed_dirty,
execonly, level);
if (new_mode.as_u64 != context->cpu_role.as_u64) {
/* EPT, and thus nested EPT, does not consume CR0, CR4, nor EFER. */
context->cpu_role.as_u64 = new_mode.as_u64;
context->root_role.word = new_mode.base.word;
context->page_fault = ept_page_fault;
context->gva_to_gpa = ept_gva_to_gpa;
context->sync_spte = ept_sync_spte;
update_permission_bitmask(context, true);
context->pkru_mask = 0;
reset_rsvds_bits_mask_ept(vcpu, context, execonly, huge_page_level);
reset_ept_shadow_zero_bits_mask(context, execonly);
}
kvm_mmu_new_pgd(vcpu, new_eptp);
}
EXPORT_SYMBOL_GPL(kvm_init_shadow_ept_mmu);
static void init_kvm_softmmu(struct kvm_vcpu *vcpu,
union kvm_cpu_role cpu_role)
{
struct kvm_mmu *context = &vcpu->arch.root_mmu;
kvm_init_shadow_mmu(vcpu, cpu_role);
context->get_guest_pgd = get_guest_cr3;
context->get_pdptr = kvm_pdptr_read;
context->inject_page_fault = kvm_inject_page_fault;
}
static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu,
union kvm_cpu_role new_mode)
{
struct kvm_mmu *g_context = &vcpu->arch.nested_mmu;
if (new_mode.as_u64 == g_context->cpu_role.as_u64)
return;
g_context->cpu_role.as_u64 = new_mode.as_u64;
g_context->get_guest_pgd = get_guest_cr3;
g_context->get_pdptr = kvm_pdptr_read;
g_context->inject_page_fault = kvm_inject_page_fault;
/*
* L2 page tables are never shadowed, so there is no need to sync
* SPTEs.
*/
g_context->sync_spte = NULL;
/*
* Note that arch.mmu->gva_to_gpa translates l2_gpa to l1_gpa using
* L1's nested page tables (e.g. EPT12). The nested translation
* of l2_gva to l1_gpa is done by arch.nested_mmu.gva_to_gpa using
* L2's page tables as the first level of translation and L1's
* nested page tables as the second level of translation. Basically
* the gva_to_gpa functions between mmu and nested_mmu are swapped.
*/
if (!is_paging(vcpu))
g_context->gva_to_gpa = nonpaging_gva_to_gpa;
else if (is_long_mode(vcpu))
g_context->gva_to_gpa = paging64_gva_to_gpa;
else if (is_pae(vcpu))
g_context->gva_to_gpa = paging64_gva_to_gpa;
else
g_context->gva_to_gpa = paging32_gva_to_gpa;
reset_guest_paging_metadata(vcpu, g_context);
}
void kvm_init_mmu(struct kvm_vcpu *vcpu)
{
struct kvm_mmu_role_regs regs = vcpu_to_role_regs(vcpu);
union kvm_cpu_role cpu_role = kvm_calc_cpu_role(vcpu, &regs);
if (mmu_is_nested(vcpu))
init_kvm_nested_mmu(vcpu, cpu_role);
else if (tdp_enabled)
init_kvm_tdp_mmu(vcpu, cpu_role);
else
init_kvm_softmmu(vcpu, cpu_role);
}
EXPORT_SYMBOL_GPL(kvm_init_mmu);
void kvm_mmu_after_set_cpuid(struct kvm_vcpu *vcpu)
{
/*
* Invalidate all MMU roles to force them to reinitialize as CPUID
* information is factored into reserved bit calculations.
*
* Correctly handling multiple vCPU models with respect to paging and
* physical address properties) in a single VM would require tracking
* all relevant CPUID information in kvm_mmu_page_role. That is very
* undesirable as it would increase the memory requirements for
* gfn_write_track (see struct kvm_mmu_page_role comments). For now
* that problem is swept under the rug; KVM's CPUID API is horrific and
* it's all but impossible to solve it without introducing a new API.
*/
vcpu->arch.root_mmu.root_role.invalid = 1;
vcpu->arch.guest_mmu.root_role.invalid = 1;
vcpu->arch.nested_mmu.root_role.invalid = 1;
vcpu->arch.root_mmu.cpu_role.ext.valid = 0;
vcpu->arch.guest_mmu.cpu_role.ext.valid = 0;
vcpu->arch.nested_mmu.cpu_role.ext.valid = 0;
kvm_mmu_reset_context(vcpu);
/*
* Changing guest CPUID after KVM_RUN is forbidden, see the comment in
* kvm_arch_vcpu_ioctl().
*/
KVM_BUG_ON(kvm_vcpu_has_run(vcpu), vcpu->kvm);
}
void kvm_mmu_reset_context(struct kvm_vcpu *vcpu)
{
kvm_mmu_unload(vcpu);
kvm_init_mmu(vcpu);
}
EXPORT_SYMBOL_GPL(kvm_mmu_reset_context);
int kvm_mmu_load(struct kvm_vcpu *vcpu)
{
int r;
r = mmu_topup_memory_caches(vcpu, !vcpu->arch.mmu->root_role.direct);
if (r)
goto out;
r = mmu_alloc_special_roots(vcpu);
if (r)
goto out;
if (vcpu->arch.mmu->root_role.direct)
r = mmu_alloc_direct_roots(vcpu);
else
r = mmu_alloc_shadow_roots(vcpu);
if (r)
goto out;
kvm_mmu_sync_roots(vcpu);
kvm_mmu_load_pgd(vcpu);
/*
* Flush any TLB entries for the new root, the provenance of the root
* is unknown. Even if KVM ensures there are no stale TLB entries
* for a freed root, in theory another hypervisor could have left
* stale entries. Flushing on alloc also allows KVM to skip the TLB
* flush when freeing a root (see kvm_tdp_mmu_put_root()).
*/
kvm_x86_call(flush_tlb_current)(vcpu);
out:
return r;
}
void kvm_mmu_unload(struct kvm_vcpu *vcpu)
{
struct kvm *kvm = vcpu->kvm;
kvm_mmu_free_roots(kvm, &vcpu->arch.root_mmu, KVM_MMU_ROOTS_ALL);
WARN_ON_ONCE(VALID_PAGE(vcpu->arch.root_mmu.root.hpa));
kvm_mmu_free_roots(kvm, &vcpu->arch.guest_mmu, KVM_MMU_ROOTS_ALL);
WARN_ON_ONCE(VALID_PAGE(vcpu->arch.guest_mmu.root.hpa));
vcpu_clear_mmio_info(vcpu, MMIO_GVA_ANY);
}
static bool is_obsolete_root(struct kvm *kvm, hpa_t root_hpa)
{
struct kvm_mmu_page *sp;
if (!VALID_PAGE(root_hpa))
return false;
/*
* When freeing obsolete roots, treat roots as obsolete if they don't
* have an associated shadow page, as it's impossible to determine if
* such roots are fresh or stale. This does mean KVM will get false
* positives and free roots that don't strictly need to be freed, but
* such false positives are relatively rare:
*
* (a) only PAE paging and nested NPT have roots without shadow pages
* (or any shadow paging flavor with a dummy root, see note below)
* (b) remote reloads due to a memslot update obsoletes _all_ roots
* (c) KVM doesn't track previous roots for PAE paging, and the guest
* is unlikely to zap an in-use PGD.
*
* Note! Dummy roots are unique in that they are obsoleted by memslot
* _creation_! See also FNAME(fetch).
*/
sp = root_to_sp(root_hpa);
return !sp || is_obsolete_sp(kvm, sp);
}
static void __kvm_mmu_free_obsolete_roots(struct kvm *kvm, struct kvm_mmu *mmu)
{
unsigned long roots_to_free = 0;
int i;
if (is_obsolete_root(kvm, mmu->root.hpa))
roots_to_free |= KVM_MMU_ROOT_CURRENT;
for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) {
if (is_obsolete_root(kvm, mmu->prev_roots[i].hpa))
roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i);
}
if (roots_to_free)
kvm_mmu_free_roots(kvm, mmu, roots_to_free);
}
void kvm_mmu_free_obsolete_roots(struct kvm_vcpu *vcpu)
{
__kvm_mmu_free_obsolete_roots(vcpu->kvm, &vcpu->arch.root_mmu);
__kvm_mmu_free_obsolete_roots(vcpu->kvm, &vcpu->arch.guest_mmu);
}
static u64 mmu_pte_write_fetch_gpte(struct kvm_vcpu *vcpu, gpa_t *gpa,
int *bytes)
{
u64 gentry = 0;
int r;
/*
* Assume that the pte write on a page table of the same type
* as the current vcpu paging mode since we update the sptes only
* when they have the same mode.
*/
if (is_pae(vcpu) && *bytes == 4) {
/* Handle a 32-bit guest writing two halves of a 64-bit gpte */
*gpa &= ~(gpa_t)7;
*bytes = 8;
}
if (*bytes == 4 || *bytes == 8) {
r = kvm_vcpu_read_guest_atomic(vcpu, *gpa, &gentry, *bytes);
if (r)
gentry = 0;
}
return gentry;
}
/*
* If we're seeing too many writes to a page, it may no longer be a page table,
* or we may be forking, in which case it is better to unmap the page.
*/
static bool detect_write_flooding(struct kvm_mmu_page *sp)
{
/*
* Skip write-flooding detected for the sp whose level is 1, because
* it can become unsync, then the guest page is not write-protected.
*/
if (sp->role.level == PG_LEVEL_4K)
return false;
atomic_inc(&sp->write_flooding_count);
return atomic_read(&sp->write_flooding_count) >= 3;
}
/*
* Misaligned accesses are too much trouble to fix up; also, they usually
* indicate a page is not used as a page table.
*/
static bool detect_write_misaligned(struct kvm_mmu_page *sp, gpa_t gpa,
int bytes)
{
unsigned offset, pte_size, misaligned;
offset = offset_in_page(gpa);
pte_size = sp->role.has_4_byte_gpte ? 4 : 8;
/*
* Sometimes, the OS only writes the last one bytes to update status
* bits, for example, in linux, andb instruction is used in clear_bit().
*/
if (!(offset & (pte_size - 1)) && bytes == 1)
return false;
misaligned = (offset ^ (offset + bytes - 1)) & ~(pte_size - 1);
misaligned |= bytes < 4;
return misaligned;
}
static u64 *get_written_sptes(struct kvm_mmu_page *sp, gpa_t gpa, int *nspte)
{
unsigned page_offset, quadrant;
u64 *spte;
int level;
page_offset = offset_in_page(gpa);
level = sp->role.level;
*nspte = 1;
if (sp->role.has_4_byte_gpte) {
page_offset <<= 1; /* 32->64 */
/*
* A 32-bit pde maps 4MB while the shadow pdes map
* only 2MB. So we need to double the offset again
* and zap two pdes instead of one.
*/
if (level == PT32_ROOT_LEVEL) {
page_offset &= ~7; /* kill rounding error */
page_offset <<= 1;
*nspte = 2;
}
quadrant = page_offset >> PAGE_SHIFT;
page_offset &= ~PAGE_MASK;
if (quadrant != sp->role.quadrant)
return NULL;
}
spte = &sp->spt[page_offset / sizeof(*spte)];
return spte;
}
void kvm_mmu_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
int bytes)
{
gfn_t gfn = gpa >> PAGE_SHIFT;
struct kvm_mmu_page *sp;
LIST_HEAD(invalid_list);
u64 entry, gentry, *spte;
int npte;
bool flush = false;
/*
* When emulating guest writes, ensure the written value is visible to
* any task that is handling page faults before checking whether or not
* KVM is shadowing a guest PTE. This ensures either KVM will create
* the correct SPTE in the page fault handler, or this task will see
* a non-zero indirect_shadow_pages. Pairs with the smp_mb() in
* account_shadowed().
*/
smp_mb();
if (!vcpu->kvm->arch.indirect_shadow_pages)
return;
write_lock(&vcpu->kvm->mmu_lock);
gentry = mmu_pte_write_fetch_gpte(vcpu, &gpa, &bytes);
++vcpu->kvm->stat.mmu_pte_write;
for_each_gfn_valid_sp_with_gptes(vcpu->kvm, sp, gfn) {
if (detect_write_misaligned(sp, gpa, bytes) ||
detect_write_flooding(sp)) {
kvm_mmu_prepare_zap_page(vcpu->kvm, sp, &invalid_list);
++vcpu->kvm->stat.mmu_flooded;
continue;
}
spte = get_written_sptes(sp, gpa, &npte);
if (!spte)
continue;
while (npte--) {
entry = *spte;
mmu_page_zap_pte(vcpu->kvm, sp, spte, NULL);
if (gentry && sp->role.level != PG_LEVEL_4K)
++vcpu->kvm->stat.mmu_pde_zapped;
if (is_shadow_present_pte(entry))
flush = true;
++spte;
}
}
kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, flush);
write_unlock(&vcpu->kvm->mmu_lock);
}
static bool is_write_to_guest_page_table(u64 error_code)
{
const u64 mask = PFERR_GUEST_PAGE_MASK | PFERR_WRITE_MASK | PFERR_PRESENT_MASK;
return (error_code & mask) == mask;
}
static int kvm_mmu_write_protect_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
u64 error_code, int *emulation_type)
{
bool direct = vcpu->arch.mmu->root_role.direct;
/*
* Do not try to unprotect and retry if the vCPU re-faulted on the same
* RIP with the same address that was previously unprotected, as doing
* so will likely put the vCPU into an infinite. E.g. if the vCPU uses
* a non-page-table modifying instruction on the PDE that points to the
* instruction, then unprotecting the gfn will unmap the instruction's
* code, i.e. make it impossible for the instruction to ever complete.
*/
if (vcpu->arch.last_retry_eip == kvm_rip_read(vcpu) &&
vcpu->arch.last_retry_addr == cr2_or_gpa)
return RET_PF_EMULATE;
/*
* Reset the unprotect+retry values that guard against infinite loops.
* The values will be refreshed if KVM explicitly unprotects a gfn and
* retries, in all other cases it's safe to retry in the future even if
* the next page fault happens on the same RIP+address.
*/
vcpu->arch.last_retry_eip = 0;
vcpu->arch.last_retry_addr = 0;
/*
* It should be impossible to reach this point with an MMIO cache hit,
* as RET_PF_WRITE_PROTECTED is returned if and only if there's a valid,
* writable memslot, and creating a memslot should invalidate the MMIO
* cache by way of changing the memslot generation. WARN and disallow
* retry if MMIO is detected, as retrying MMIO emulation is pointless
* and could put the vCPU into an infinite loop because the processor
* will keep faulting on the non-existent MMIO address.
*/
if (WARN_ON_ONCE(mmio_info_in_cache(vcpu, cr2_or_gpa, direct)))
return RET_PF_EMULATE;
/*
* Before emulating the instruction, check to see if the access was due
* to a read-only violation while the CPU was walking non-nested NPT
* page tables, i.e. for a direct MMU, for _guest_ page tables in L1.
* If L1 is sharing (a subset of) its page tables with L2, e.g. by
* having nCR3 share lower level page tables with hCR3, then when KVM
* (L0) write-protects the nested NPTs, i.e. npt12 entries, KVM is also
* unknowingly write-protecting L1's guest page tables, which KVM isn't
* shadowing.
*
* Because the CPU (by default) walks NPT page tables using a write
* access (to ensure the CPU can do A/D updates), page walks in L1 can
* trigger write faults for the above case even when L1 isn't modifying
* PTEs. As a result, KVM will unnecessarily emulate (or at least, try
* to emulate) an excessive number of L1 instructions; because L1's MMU
* isn't shadowed by KVM, there is no need to write-protect L1's gPTEs
* and thus no need to emulate in order to guarantee forward progress.
*
* Try to unprotect the gfn, i.e. zap any shadow pages, so that L1 can
* proceed without triggering emulation. If one or more shadow pages
* was zapped, skip emulation and resume L1 to let it natively execute
* the instruction. If no shadow pages were zapped, then the write-
* fault is due to something else entirely, i.e. KVM needs to emulate,
* as resuming the guest will put it into an infinite loop.
*
* Note, this code also applies to Intel CPUs, even though it is *very*
* unlikely that an L1 will share its page tables (IA32/PAE/paging64
* format) with L2's page tables (EPT format).
*
* For indirect MMUs, i.e. if KVM is shadowing the current MMU, try to
* unprotect the gfn and retry if an event is awaiting reinjection. If
* KVM emulates multiple instructions before completing event injection,
* the event could be delayed beyond what is architecturally allowed,
* e.g. KVM could inject an IRQ after the TPR has been raised.
*/
if (((direct && is_write_to_guest_page_table(error_code)) ||
(!direct && kvm_event_needs_reinjection(vcpu))) &&
kvm_mmu_unprotect_gfn_and_retry(vcpu, cr2_or_gpa))
return RET_PF_RETRY;
/*
* The gfn is write-protected, but if KVM detects its emulating an
* instruction that is unlikely to be used to modify page tables, or if
* emulation fails, KVM can try to unprotect the gfn and let the CPU
* re-execute the instruction that caused the page fault. Do not allow
* retrying an instruction from a nested guest as KVM is only explicitly
* shadowing L1's page tables, i.e. unprotecting something for L1 isn't
* going to magically fix whatever issue caused L2 to fail.
*/
if (!is_guest_mode(vcpu))
*emulation_type |= EMULTYPE_ALLOW_RETRY_PF;
return RET_PF_EMULATE;
}
int noinline kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 error_code,
void *insn, int insn_len)
{
int r, emulation_type = EMULTYPE_PF;
bool direct = vcpu->arch.mmu->root_role.direct;
if (WARN_ON_ONCE(!VALID_PAGE(vcpu->arch.mmu->root.hpa)))
return RET_PF_RETRY;
/*
* Except for reserved faults (emulated MMIO is shared-only), set the
* PFERR_PRIVATE_ACCESS flag for software-protected VMs based on the gfn's
* current attributes, which are the source of truth for such VMs. Note,
* this wrong for nested MMUs as the GPA is an L2 GPA, but KVM doesn't
* currently supported nested virtualization (among many other things)
* for software-protected VMs.
*/
if (IS_ENABLED(CONFIG_KVM_SW_PROTECTED_VM) &&
!(error_code & PFERR_RSVD_MASK) &&
vcpu->kvm->arch.vm_type == KVM_X86_SW_PROTECTED_VM &&
kvm_mem_is_private(vcpu->kvm, gpa_to_gfn(cr2_or_gpa)))
error_code |= PFERR_PRIVATE_ACCESS;
r = RET_PF_INVALID;
if (unlikely(error_code & PFERR_RSVD_MASK)) {
if (WARN_ON_ONCE(error_code & PFERR_PRIVATE_ACCESS))
return -EFAULT;
r = handle_mmio_page_fault(vcpu, cr2_or_gpa, direct);
if (r == RET_PF_EMULATE)
goto emulate;
}
if (r == RET_PF_INVALID) {
vcpu->stat.pf_taken++;
r = kvm_mmu_do_page_fault(vcpu, cr2_or_gpa, error_code, false,
&emulation_type, NULL);
if (KVM_BUG_ON(r == RET_PF_INVALID, vcpu->kvm))
return -EIO;
}
if (r < 0)
return r;
if (r == RET_PF_WRITE_PROTECTED)
r = kvm_mmu_write_protect_fault(vcpu, cr2_or_gpa, error_code,
&emulation_type);
if (r == RET_PF_FIXED)
vcpu->stat.pf_fixed++;
else if (r == RET_PF_EMULATE)
vcpu->stat.pf_emulate++;
else if (r == RET_PF_SPURIOUS)
vcpu->stat.pf_spurious++;
if (r != RET_PF_EMULATE)
return 1;
emulate:
return x86_emulate_instruction(vcpu, cr2_or_gpa, emulation_type, insn,
insn_len);
}
EXPORT_SYMBOL_GPL(kvm_mmu_page_fault);
void kvm_mmu_print_sptes(struct kvm_vcpu *vcpu, gpa_t gpa, const char *msg)
{
u64 sptes[PT64_ROOT_MAX_LEVEL + 1];
int root_level, leaf, level;
leaf = get_sptes_lockless(vcpu, gpa, sptes, &root_level);
if (unlikely(leaf < 0))
return;
pr_err("%s %llx", msg, gpa);
for (level = root_level; level >= leaf; level--)
pr_cont(", spte[%d] = 0x%llx", level, sptes[level]);
pr_cont("\n");
}
EXPORT_SYMBOL_GPL(kvm_mmu_print_sptes);
static void __kvm_mmu_invalidate_addr(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
u64 addr, hpa_t root_hpa)
{
struct kvm_shadow_walk_iterator iterator;
vcpu_clear_mmio_info(vcpu, addr);
/*
* Walking and synchronizing SPTEs both assume they are operating in
* the context of the current MMU, and would need to be reworked if
* this is ever used to sync the guest_mmu, e.g. to emulate INVEPT.
*/
if (WARN_ON_ONCE(mmu != vcpu->arch.mmu))
return;
if (!VALID_PAGE(root_hpa))
return;
write_lock(&vcpu->kvm->mmu_lock);
for_each_shadow_entry_using_root(vcpu, root_hpa, addr, iterator) {
struct kvm_mmu_page *sp = sptep_to_sp(iterator.sptep);
if (sp->unsync) {
int ret = kvm_sync_spte(vcpu, sp, iterator.index);
if (ret < 0)
mmu_page_zap_pte(vcpu->kvm, sp, iterator.sptep, NULL);
if (ret)
kvm_flush_remote_tlbs_sptep(vcpu->kvm, iterator.sptep);
}
if (!sp->unsync_children)
break;
}
write_unlock(&vcpu->kvm->mmu_lock);
}
void kvm_mmu_invalidate_addr(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
u64 addr, unsigned long roots)
{
int i;
WARN_ON_ONCE(roots & ~KVM_MMU_ROOTS_ALL);
/* It's actually a GPA for vcpu->arch.guest_mmu. */
if (mmu != &vcpu->arch.guest_mmu) {
/* INVLPG on a non-canonical address is a NOP according to the SDM. */
if (is_noncanonical_address(addr, vcpu))
return;
kvm_x86_call(flush_tlb_gva)(vcpu, addr);
}
if (!mmu->sync_spte)
return;
if (roots & KVM_MMU_ROOT_CURRENT)
__kvm_mmu_invalidate_addr(vcpu, mmu, addr, mmu->root.hpa);
for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) {
if (roots & KVM_MMU_ROOT_PREVIOUS(i))
__kvm_mmu_invalidate_addr(vcpu, mmu, addr, mmu->prev_roots[i].hpa);
}
}
EXPORT_SYMBOL_GPL(kvm_mmu_invalidate_addr);
void kvm_mmu_invlpg(struct kvm_vcpu *vcpu, gva_t gva)
{
/*
* INVLPG is required to invalidate any global mappings for the VA,
* irrespective of PCID. Blindly sync all roots as it would take
* roughly the same amount of work/time to determine whether any of the
* previous roots have a global mapping.
*
* Mappings not reachable via the current or previous cached roots will
* be synced when switching to that new cr3, so nothing needs to be
* done here for them.
*/
kvm_mmu_invalidate_addr(vcpu, vcpu->arch.walk_mmu, gva, KVM_MMU_ROOTS_ALL);
++vcpu->stat.invlpg;
}
EXPORT_SYMBOL_GPL(kvm_mmu_invlpg);
void kvm_mmu_invpcid_gva(struct kvm_vcpu *vcpu, gva_t gva, unsigned long pcid)
{
struct kvm_mmu *mmu = vcpu->arch.mmu;
unsigned long roots = 0;
uint i;
if (pcid == kvm_get_active_pcid(vcpu))
roots |= KVM_MMU_ROOT_CURRENT;
for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) {
if (VALID_PAGE(mmu->prev_roots[i].hpa) &&
pcid == kvm_get_pcid(vcpu, mmu->prev_roots[i].pgd))
roots |= KVM_MMU_ROOT_PREVIOUS(i);
}
if (roots)
kvm_mmu_invalidate_addr(vcpu, mmu, gva, roots);
++vcpu->stat.invlpg;
/*
* Mappings not reachable via the current cr3 or the prev_roots will be
* synced when switching to that cr3, so nothing needs to be done here
* for them.
*/
}
void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level,
int tdp_max_root_level, int tdp_huge_page_level)
{
tdp_enabled = enable_tdp;
tdp_root_level = tdp_forced_root_level;
max_tdp_level = tdp_max_root_level;
#ifdef CONFIG_X86_64
tdp_mmu_enabled = tdp_mmu_allowed && tdp_enabled;
#endif
/*
* max_huge_page_level reflects KVM's MMU capabilities irrespective
* of kernel support, e.g. KVM may be capable of using 1GB pages when
* the kernel is not. But, KVM never creates a page size greater than
* what is used by the kernel for any given HVA, i.e. the kernel's
* capabilities are ultimately consulted by kvm_mmu_hugepage_adjust().
*/
if (tdp_enabled)
max_huge_page_level = tdp_huge_page_level;
else if (boot_cpu_has(X86_FEATURE_GBPAGES))
max_huge_page_level = PG_LEVEL_1G;
else
max_huge_page_level = PG_LEVEL_2M;
}
EXPORT_SYMBOL_GPL(kvm_configure_mmu);
static void free_mmu_pages(struct kvm_mmu *mmu)
{
if (!tdp_enabled && mmu->pae_root)
set_memory_encrypted((unsigned long)mmu->pae_root, 1);
free_page((unsigned long)mmu->pae_root);
free_page((unsigned long)mmu->pml4_root);
free_page((unsigned long)mmu->pml5_root);
}
static int __kvm_mmu_create(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
{
struct page *page;
int i;
mmu->root.hpa = INVALID_PAGE;
mmu->root.pgd = 0;
for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
mmu->prev_roots[i] = KVM_MMU_ROOT_INFO_INVALID;
/* vcpu->arch.guest_mmu isn't used when !tdp_enabled. */
if (!tdp_enabled && mmu == &vcpu->arch.guest_mmu)
return 0;
/*
* When using PAE paging, the four PDPTEs are treated as 'root' pages,
* while the PDP table is a per-vCPU construct that's allocated at MMU
* creation. When emulating 32-bit mode, cr3 is only 32 bits even on
* x86_64. Therefore we need to allocate the PDP table in the first
* 4GB of memory, which happens to fit the DMA32 zone. TDP paging
* generally doesn't use PAE paging and can skip allocating the PDP
* table. The main exception, handled here, is SVM's 32-bit NPT. The
* other exception is for shadowing L1's 32-bit or PAE NPT on 64-bit
* KVM; that horror is handled on-demand by mmu_alloc_special_roots().
*/
if (tdp_enabled && kvm_mmu_get_tdp_level(vcpu) > PT32E_ROOT_LEVEL)
return 0;
page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_DMA32);
if (!page)
return -ENOMEM;
mmu->pae_root = page_address(page);
/*
* CR3 is only 32 bits when PAE paging is used, thus it's impossible to
* get the CPU to treat the PDPTEs as encrypted. Decrypt the page so
* that KVM's writes and the CPU's reads get along. Note, this is
* only necessary when using shadow paging, as 64-bit NPT can get at
* the C-bit even when shadowing 32-bit NPT, and SME isn't supported
* by 32-bit kernels (when KVM itself uses 32-bit NPT).
*/
if (!tdp_enabled)
set_memory_decrypted((unsigned long)mmu->pae_root, 1);
else
WARN_ON_ONCE(shadow_me_value);
for (i = 0; i < 4; ++i)
mmu->pae_root[i] = INVALID_PAE_ROOT;
return 0;
}
int kvm_mmu_create(struct kvm_vcpu *vcpu)
{
int ret;
vcpu->arch.mmu_pte_list_desc_cache.kmem_cache = pte_list_desc_cache;
vcpu->arch.mmu_pte_list_desc_cache.gfp_zero = __GFP_ZERO;
vcpu->arch.mmu_page_header_cache.kmem_cache = mmu_page_header_cache;
vcpu->arch.mmu_page_header_cache.gfp_zero = __GFP_ZERO;
vcpu->arch.mmu_shadow_page_cache.init_value =
SHADOW_NONPRESENT_VALUE;
if (!vcpu->arch.mmu_shadow_page_cache.init_value)
vcpu->arch.mmu_shadow_page_cache.gfp_zero = __GFP_ZERO;
vcpu->arch.mmu = &vcpu->arch.root_mmu;
vcpu->arch.walk_mmu = &vcpu->arch.root_mmu;
ret = __kvm_mmu_create(vcpu, &vcpu->arch.guest_mmu);
if (ret)
return ret;
ret = __kvm_mmu_create(vcpu, &vcpu->arch.root_mmu);
if (ret)
goto fail_allocate_root;
return ret;
fail_allocate_root:
free_mmu_pages(&vcpu->arch.guest_mmu);
return ret;
}
#define BATCH_ZAP_PAGES 10
static void kvm_zap_obsolete_pages(struct kvm *kvm)
{
struct kvm_mmu_page *sp, *node;
int nr_zapped, batch = 0;
bool unstable;
restart:
list_for_each_entry_safe_reverse(sp, node,
&kvm->arch.active_mmu_pages, link) {
/*
* No obsolete valid page exists before a newly created page
* since active_mmu_pages is a FIFO list.
*/
if (!is_obsolete_sp(kvm, sp))
break;
/*
* Invalid pages should never land back on the list of active
* pages. Skip the bogus page, otherwise we'll get stuck in an
* infinite loop if the page gets put back on the list (again).
*/
if (WARN_ON_ONCE(sp->role.invalid))
continue;
/*
* No need to flush the TLB since we're only zapping shadow
* pages with an obsolete generation number and all vCPUS have
* loaded a new root, i.e. the shadow pages being zapped cannot
* be in active use by the guest.
*/
if (batch >= BATCH_ZAP_PAGES &&
cond_resched_rwlock_write(&kvm->mmu_lock)) {
batch = 0;
goto restart;
}
unstable = __kvm_mmu_prepare_zap_page(kvm, sp,
&kvm->arch.zapped_obsolete_pages, &nr_zapped);
batch += nr_zapped;
if (unstable)
goto restart;
}
/*
* Kick all vCPUs (via remote TLB flush) before freeing the page tables
* to ensure KVM is not in the middle of a lockless shadow page table
* walk, which may reference the pages. The remote TLB flush itself is
* not required and is simply a convenient way to kick vCPUs as needed.
* KVM performs a local TLB flush when allocating a new root (see
* kvm_mmu_load()), and the reload in the caller ensure no vCPUs are
* running with an obsolete MMU.
*/
kvm_mmu_commit_zap_page(kvm, &kvm->arch.zapped_obsolete_pages);
}
/*
* Fast invalidate all shadow pages and use lock-break technique
* to zap obsolete pages.
*
* It's required when memslot is being deleted or VM is being
* destroyed, in these cases, we should ensure that KVM MMU does
* not use any resource of the being-deleted slot or all slots
* after calling the function.
*/
static void kvm_mmu_zap_all_fast(struct kvm *kvm)
{
lockdep_assert_held(&kvm->slots_lock);
write_lock(&kvm->mmu_lock);
trace_kvm_mmu_zap_all_fast(kvm);
/*
* Toggle mmu_valid_gen between '0' and '1'. Because slots_lock is
* held for the entire duration of zapping obsolete pages, it's
* impossible for there to be multiple invalid generations associated
* with *valid* shadow pages at any given time, i.e. there is exactly
* one valid generation and (at most) one invalid generation.
*/
kvm->arch.mmu_valid_gen = kvm->arch.mmu_valid_gen ? 0 : 1;
/*
* In order to ensure all vCPUs drop their soon-to-be invalid roots,
* invalidating TDP MMU roots must be done while holding mmu_lock for
* write and in the same critical section as making the reload request,
* e.g. before kvm_zap_obsolete_pages() could drop mmu_lock and yield.
*/
if (tdp_mmu_enabled)
kvm_tdp_mmu_invalidate_all_roots(kvm);
/*
* Notify all vcpus to reload its shadow page table and flush TLB.
* Then all vcpus will switch to new shadow page table with the new
* mmu_valid_gen.
*
* Note: we need to do this under the protection of mmu_lock,
* otherwise, vcpu would purge shadow page but miss tlb flush.
*/
kvm_make_all_cpus_request(kvm, KVM_REQ_MMU_FREE_OBSOLETE_ROOTS);
kvm_zap_obsolete_pages(kvm);
write_unlock(&kvm->mmu_lock);
/*
* Zap the invalidated TDP MMU roots, all SPTEs must be dropped before
* returning to the caller, e.g. if the zap is in response to a memslot
* deletion, mmu_notifier callbacks will be unable to reach the SPTEs
* associated with the deleted memslot once the update completes, and
* Deferring the zap until the final reference to the root is put would
* lead to use-after-free.
*/
if (tdp_mmu_enabled)
kvm_tdp_mmu_zap_invalidated_roots(kvm);
}
static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
{
return unlikely(!list_empty_careful(&kvm->arch.zapped_obsolete_pages));
}
void kvm_mmu_init_vm(struct kvm *kvm)
{
kvm->arch.shadow_mmio_value = shadow_mmio_value;
INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
INIT_LIST_HEAD(&kvm->arch.zapped_obsolete_pages);
INIT_LIST_HEAD(&kvm->arch.possible_nx_huge_pages);
spin_lock_init(&kvm->arch.mmu_unsync_pages_lock);
if (tdp_mmu_enabled)
kvm_mmu_init_tdp_mmu(kvm);
kvm->arch.split_page_header_cache.kmem_cache = mmu_page_header_cache;
kvm->arch.split_page_header_cache.gfp_zero = __GFP_ZERO;
kvm->arch.split_shadow_page_cache.gfp_zero = __GFP_ZERO;
kvm->arch.split_desc_cache.kmem_cache = pte_list_desc_cache;
kvm->arch.split_desc_cache.gfp_zero = __GFP_ZERO;
}
static void mmu_free_vm_memory_caches(struct kvm *kvm)
{
kvm_mmu_free_memory_cache(&kvm->arch.split_desc_cache);
kvm_mmu_free_memory_cache(&kvm->arch.split_page_header_cache);
kvm_mmu_free_memory_cache(&kvm->arch.split_shadow_page_cache);
}
void kvm_mmu_uninit_vm(struct kvm *kvm)
{
if (tdp_mmu_enabled)
kvm_mmu_uninit_tdp_mmu(kvm);
mmu_free_vm_memory_caches(kvm);
}
static bool kvm_rmap_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
{
const struct kvm_memory_slot *memslot;
struct kvm_memslots *slots;
struct kvm_memslot_iter iter;
bool flush = false;
gfn_t start, end;
int i;
if (!kvm_memslots_have_rmaps(kvm))
return flush;
for (i = 0; i < kvm_arch_nr_memslot_as_ids(kvm); i++) {
slots = __kvm_memslots(kvm, i);
kvm_for_each_memslot_in_gfn_range(&iter, slots, gfn_start, gfn_end) {
memslot = iter.slot;
start = max(gfn_start, memslot->base_gfn);
end = min(gfn_end, memslot->base_gfn + memslot->npages);
if (WARN_ON_ONCE(start >= end))
continue;
flush = __kvm_rmap_zap_gfn_range(kvm, memslot, start,
end, true, flush);
}
}
return flush;
}
/*
* Invalidate (zap) SPTEs that cover GFNs from gfn_start and up to gfn_end
* (not including it)
*/
void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
{
bool flush;
if (WARN_ON_ONCE(gfn_end <= gfn_start))
return;
write_lock(&kvm->mmu_lock);
kvm_mmu_invalidate_begin(kvm);
kvm_mmu_invalidate_range_add(kvm, gfn_start, gfn_end);
flush = kvm_rmap_zap_gfn_range(kvm, gfn_start, gfn_end);
if (tdp_mmu_enabled)
flush = kvm_tdp_mmu_zap_leafs(kvm, gfn_start, gfn_end, flush);
if (flush)
kvm_flush_remote_tlbs_range(kvm, gfn_start, gfn_end - gfn_start);
kvm_mmu_invalidate_end(kvm);
write_unlock(&kvm->mmu_lock);
}
static bool slot_rmap_write_protect(struct kvm *kvm,
struct kvm_rmap_head *rmap_head,
const struct kvm_memory_slot *slot)
{
return rmap_write_protect(rmap_head, false);
}
void kvm_mmu_slot_remove_write_access(struct kvm *kvm,
const struct kvm_memory_slot *memslot,
int start_level)
{
if (kvm_memslots_have_rmaps(kvm)) {
write_lock(&kvm->mmu_lock);
walk_slot_rmaps(kvm, memslot, slot_rmap_write_protect,
start_level, KVM_MAX_HUGEPAGE_LEVEL, false);
write_unlock(&kvm->mmu_lock);
}
if (tdp_mmu_enabled) {
read_lock(&kvm->mmu_lock);
kvm_tdp_mmu_wrprot_slot(kvm, memslot, start_level);
read_unlock(&kvm->mmu_lock);
}
}
static inline bool need_topup(struct kvm_mmu_memory_cache *cache, int min)
{
return kvm_mmu_memory_cache_nr_free_objects(cache) < min;
}
static bool need_topup_split_caches_or_resched(struct kvm *kvm)
{
if (need_resched() || rwlock_needbreak(&kvm->mmu_lock))
return true;
/*
* In the worst case, SPLIT_DESC_CACHE_MIN_NR_OBJECTS descriptors are needed
* to split a single huge page. Calculating how many are actually needed
* is possible but not worth the complexity.
*/
return need_topup(&kvm->arch.split_desc_cache, SPLIT_DESC_CACHE_MIN_NR_OBJECTS) ||
need_topup(&kvm->arch.split_page_header_cache, 1) ||
need_topup(&kvm->arch.split_shadow_page_cache, 1);
}
static int topup_split_caches(struct kvm *kvm)
{
/*
* Allocating rmap list entries when splitting huge pages for nested
* MMUs is uncommon as KVM needs to use a list if and only if there is
* more than one rmap entry for a gfn, i.e. requires an L1 gfn to be
* aliased by multiple L2 gfns and/or from multiple nested roots with
* different roles. Aliasing gfns when using TDP is atypical for VMMs;
* a few gfns are often aliased during boot, e.g. when remapping BIOS,
* but aliasing rarely occurs post-boot or for many gfns. If there is
* only one rmap entry, rmap->val points directly at that one entry and
* doesn't need to allocate a list. Buffer the cache by the default
* capacity so that KVM doesn't have to drop mmu_lock to topup if KVM
* encounters an aliased gfn or two.
*/
const int capacity = SPLIT_DESC_CACHE_MIN_NR_OBJECTS +
KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE;
int r;
lockdep_assert_held(&kvm->slots_lock);
r = __kvm_mmu_topup_memory_cache(&kvm->arch.split_desc_cache, capacity,
SPLIT_DESC_CACHE_MIN_NR_OBJECTS);
if (r)
return r;
r = kvm_mmu_topup_memory_cache(&kvm->arch.split_page_header_cache, 1);
if (r)
return r;
return kvm_mmu_topup_memory_cache(&kvm->arch.split_shadow_page_cache, 1);
}
static struct kvm_mmu_page *shadow_mmu_get_sp_for_split(struct kvm *kvm, u64 *huge_sptep)
{
struct kvm_mmu_page *huge_sp = sptep_to_sp(huge_sptep);
struct shadow_page_caches caches = {};
union kvm_mmu_page_role role;
unsigned int access;
gfn_t gfn;
gfn = kvm_mmu_page_get_gfn(huge_sp, spte_index(huge_sptep));
access = kvm_mmu_page_get_access(huge_sp, spte_index(huge_sptep));
/*
* Note, huge page splitting always uses direct shadow pages, regardless
* of whether the huge page itself is mapped by a direct or indirect
* shadow page, since the huge page region itself is being directly
* mapped with smaller pages.
*/
role = kvm_mmu_child_role(huge_sptep, /*direct=*/true, access);
/* Direct SPs do not require a shadowed_info_cache. */
caches.page_header_cache = &kvm->arch.split_page_header_cache;
caches.shadow_page_cache = &kvm->arch.split_shadow_page_cache;
/* Safe to pass NULL for vCPU since requesting a direct SP. */
return __kvm_mmu_get_shadow_page(kvm, NULL, &caches, gfn, role);
}
static void shadow_mmu_split_huge_page(struct kvm *kvm,
const struct kvm_memory_slot *slot,
u64 *huge_sptep)
{
struct kvm_mmu_memory_cache *cache = &kvm->arch.split_desc_cache;
u64 huge_spte = READ_ONCE(*huge_sptep);
struct kvm_mmu_page *sp;
bool flush = false;
u64 *sptep, spte;
gfn_t gfn;
int index;
sp = shadow_mmu_get_sp_for_split(kvm, huge_sptep);
for (index = 0; index < SPTE_ENT_PER_PAGE; index++) {
sptep = &sp->spt[index];
gfn = kvm_mmu_page_get_gfn(sp, index);
/*
* The SP may already have populated SPTEs, e.g. if this huge
* page is aliased by multiple sptes with the same access
* permissions. These entries are guaranteed to map the same
* gfn-to-pfn translation since the SP is direct, so no need to
* modify them.
*
* However, if a given SPTE points to a lower level page table,
* that lower level page table may only be partially populated.
* Installing such SPTEs would effectively unmap a potion of the
* huge page. Unmapping guest memory always requires a TLB flush
* since a subsequent operation on the unmapped regions would
* fail to detect the need to flush.
*/
if (is_shadow_present_pte(*sptep)) {
flush |= !is_last_spte(*sptep, sp->role.level);
continue;
}
spte = make_huge_page_split_spte(kvm, huge_spte, sp->role, index);
mmu_spte_set(sptep, spte);
__rmap_add(kvm, cache, slot, sptep, gfn, sp->role.access);
}
__link_shadow_page(kvm, cache, huge_sptep, sp, flush);
}
static int shadow_mmu_try_split_huge_page(struct kvm *kvm,
const struct kvm_memory_slot *slot,
u64 *huge_sptep)
{
struct kvm_mmu_page *huge_sp = sptep_to_sp(huge_sptep);
int level, r = 0;
gfn_t gfn;
u64 spte;
/* Grab information for the tracepoint before dropping the MMU lock. */
gfn = kvm_mmu_page_get_gfn(huge_sp, spte_index(huge_sptep));
level = huge_sp->role.level;
spte = *huge_sptep;
if (kvm_mmu_available_pages(kvm) <= KVM_MIN_FREE_MMU_PAGES) {
r = -ENOSPC;
goto out;
}
if (need_topup_split_caches_or_resched(kvm)) {
write_unlock(&kvm->mmu_lock);
cond_resched();
/*
* If the topup succeeds, return -EAGAIN to indicate that the
* rmap iterator should be restarted because the MMU lock was
* dropped.
*/
r = topup_split_caches(kvm) ?: -EAGAIN;
write_lock(&kvm->mmu_lock);
goto out;
}
shadow_mmu_split_huge_page(kvm, slot, huge_sptep);
out:
trace_kvm_mmu_split_huge_page(gfn, spte, level, r);
return r;
}
static bool shadow_mmu_try_split_huge_pages(struct kvm *kvm,
struct kvm_rmap_head *rmap_head,
const struct kvm_memory_slot *slot)
{
struct rmap_iterator iter;
struct kvm_mmu_page *sp;
u64 *huge_sptep;
int r;
restart:
for_each_rmap_spte(rmap_head, &iter, huge_sptep) {
sp = sptep_to_sp(huge_sptep);
/* TDP MMU is enabled, so rmap only contains nested MMU SPs. */
if (WARN_ON_ONCE(!sp->role.guest_mode))
continue;
/* The rmaps should never contain non-leaf SPTEs. */
if (WARN_ON_ONCE(!is_large_pte(*huge_sptep)))
continue;
/* SPs with level >PG_LEVEL_4K should never by unsync. */
if (WARN_ON_ONCE(sp->unsync))
continue;
/* Don't bother splitting huge pages on invalid SPs. */
if (sp->role.invalid)
continue;
r = shadow_mmu_try_split_huge_page(kvm, slot, huge_sptep);
/*
* The split succeeded or needs to be retried because the MMU
* lock was dropped. Either way, restart the iterator to get it
* back into a consistent state.
*/
if (!r || r == -EAGAIN)
goto restart;
/* The split failed and shouldn't be retried (e.g. -ENOMEM). */
break;
}
return false;
}
static void kvm_shadow_mmu_try_split_huge_pages(struct kvm *kvm,
const struct kvm_memory_slot *slot,
gfn_t start, gfn_t end,
int target_level)
{
int level;
/*
* Split huge pages starting with KVM_MAX_HUGEPAGE_LEVEL and working
* down to the target level. This ensures pages are recursively split
* all the way to the target level. There's no need to split pages
* already at the target level.
*/
for (level = KVM_MAX_HUGEPAGE_LEVEL; level > target_level; level--)
__walk_slot_rmaps(kvm, slot, shadow_mmu_try_split_huge_pages,
level, level, start, end - 1, true, true, false);
}
/* Must be called with the mmu_lock held in write-mode. */
void kvm_mmu_try_split_huge_pages(struct kvm *kvm,
const struct kvm_memory_slot *memslot,
u64 start, u64 end,
int target_level)
{
if (!tdp_mmu_enabled)
return;
if (kvm_memslots_have_rmaps(kvm))
kvm_shadow_mmu_try_split_huge_pages(kvm, memslot, start, end, target_level);
kvm_tdp_mmu_try_split_huge_pages(kvm, memslot, start, end, target_level, false);
/*
* A TLB flush is unnecessary at this point for the same reasons as in
* kvm_mmu_slot_try_split_huge_pages().
*/
}
void kvm_mmu_slot_try_split_huge_pages(struct kvm *kvm,
const struct kvm_memory_slot *memslot,
int target_level)
{
u64 start = memslot->base_gfn;
u64 end = start + memslot->npages;
if (!tdp_mmu_enabled)
return;
if (kvm_memslots_have_rmaps(kvm)) {
write_lock(&kvm->mmu_lock);
kvm_shadow_mmu_try_split_huge_pages(kvm, memslot, start, end, target_level);
write_unlock(&kvm->mmu_lock);
}
read_lock(&kvm->mmu_lock);
kvm_tdp_mmu_try_split_huge_pages(kvm, memslot, start, end, target_level, true);
read_unlock(&kvm->mmu_lock);
/*
* No TLB flush is necessary here. KVM will flush TLBs after
* write-protecting and/or clearing dirty on the newly split SPTEs to
* ensure that guest writes are reflected in the dirty log before the
* ioctl to enable dirty logging on this memslot completes. Since the
* split SPTEs retain the write and dirty bits of the huge SPTE, it is
* safe for KVM to decide if a TLB flush is necessary based on the split
* SPTEs.
*/
}
static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm,
struct kvm_rmap_head *rmap_head,
const struct kvm_memory_slot *slot)
{
u64 *sptep;
struct rmap_iterator iter;
int need_tlb_flush = 0;
struct kvm_mmu_page *sp;
restart:
for_each_rmap_spte(rmap_head, &iter, sptep) {
sp = sptep_to_sp(sptep);
/*
* We cannot do huge page mapping for indirect shadow pages,
* which are found on the last rmap (level = 1) when not using
* tdp; such shadow pages are synced with the page table in
* the guest, and the guest page table is using 4K page size
* mapping if the indirect sp has level = 1.
*/
if (sp->role.direct &&
sp->role.level < kvm_mmu_max_mapping_level(kvm, slot, sp->gfn,
PG_LEVEL_NUM)) {
kvm_zap_one_rmap_spte(kvm, rmap_head, sptep);
if (kvm_available_flush_remote_tlbs_range())
kvm_flush_remote_tlbs_sptep(kvm, sptep);
else
need_tlb_flush = 1;
goto restart;
}
}
return need_tlb_flush;
}
EXPORT_SYMBOL_GPL(kvm_zap_gfn_range);
static void kvm_rmap_zap_collapsible_sptes(struct kvm *kvm,
const struct kvm_memory_slot *slot)
{
/*
* Note, use KVM_MAX_HUGEPAGE_LEVEL - 1 since there's no need to zap
* pages that are already mapped at the maximum hugepage level.
*/
if (walk_slot_rmaps(kvm, slot, kvm_mmu_zap_collapsible_spte,
PG_LEVEL_4K, KVM_MAX_HUGEPAGE_LEVEL - 1, true))
kvm_flush_remote_tlbs_memslot(kvm, slot);
}
void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
const struct kvm_memory_slot *slot)
{
if (kvm_memslots_have_rmaps(kvm)) {
write_lock(&kvm->mmu_lock);
kvm_rmap_zap_collapsible_sptes(kvm, slot);
write_unlock(&kvm->mmu_lock);
}
if (tdp_mmu_enabled) {
read_lock(&kvm->mmu_lock);
kvm_tdp_mmu_zap_collapsible_sptes(kvm, slot);
read_unlock(&kvm->mmu_lock);
}
}
void kvm_mmu_slot_leaf_clear_dirty(struct kvm *kvm,
const struct kvm_memory_slot *memslot)
{
if (kvm_memslots_have_rmaps(kvm)) {
write_lock(&kvm->mmu_lock);
/*
* Clear dirty bits only on 4k SPTEs since the legacy MMU only
* support dirty logging at a 4k granularity.
*/
walk_slot_rmaps_4k(kvm, memslot, __rmap_clear_dirty, false);
write_unlock(&kvm->mmu_lock);
}
if (tdp_mmu_enabled) {
read_lock(&kvm->mmu_lock);
kvm_tdp_mmu_clear_dirty_slot(kvm, memslot);
read_unlock(&kvm->mmu_lock);
}
/*
* The caller will flush the TLBs after this function returns.
*
* It's also safe to flush TLBs out of mmu lock here as currently this
* function is only used for dirty logging, in which case flushing TLB
* out of mmu lock also guarantees no dirty pages will be lost in
* dirty_bitmap.
*/
}
static void kvm_mmu_zap_all(struct kvm *kvm)
{
struct kvm_mmu_page *sp, *node;
LIST_HEAD(invalid_list);
int ign;
write_lock(&kvm->mmu_lock);
restart:
list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) {
if (WARN_ON_ONCE(sp->role.invalid))
continue;
if (__kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list, &ign))
goto restart;
if (cond_resched_rwlock_write(&kvm->mmu_lock))
goto restart;
}
kvm_mmu_commit_zap_page(kvm, &invalid_list);
if (tdp_mmu_enabled)
kvm_tdp_mmu_zap_all(kvm);
write_unlock(&kvm->mmu_lock);
}
void kvm_arch_flush_shadow_all(struct kvm *kvm)
{
kvm_mmu_zap_all(kvm);
}
static void kvm_mmu_zap_memslot_pages_and_flush(struct kvm *kvm,
struct kvm_memory_slot *slot,
bool flush)
{
LIST_HEAD(invalid_list);
unsigned long i;
if (list_empty(&kvm->arch.active_mmu_pages))
goto out_flush;
/*
* Since accounting information is stored in struct kvm_arch_memory_slot,
* shadow pages deletion (e.g. unaccount_shadowed()) requires that all
* gfns with a shadow page have a corresponding memslot. Do so before
* the memslot goes away.
*/
for (i = 0; i < slot->npages; i++) {
struct kvm_mmu_page *sp;
gfn_t gfn = slot->base_gfn + i;
for_each_gfn_valid_sp(kvm, sp, gfn)
kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) {
kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush);
flush = false;
cond_resched_rwlock_write(&kvm->mmu_lock);
}
}
out_flush:
kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush);
}
static void kvm_mmu_zap_memslot(struct kvm *kvm,
struct kvm_memory_slot *slot)
{
struct kvm_gfn_range range = {
.slot = slot,
.start = slot->base_gfn,
.end = slot->base_gfn + slot->npages,
.may_block = true,
};
bool flush;
write_lock(&kvm->mmu_lock);
flush = kvm_unmap_gfn_range(kvm, &range);
kvm_mmu_zap_memslot_pages_and_flush(kvm, slot, flush);
write_unlock(&kvm->mmu_lock);
}
static inline bool kvm_memslot_flush_zap_all(struct kvm *kvm)
{
return kvm->arch.vm_type == KVM_X86_DEFAULT_VM &&
kvm_check_has_quirk(kvm, KVM_X86_QUIRK_SLOT_ZAP_ALL);
}
void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
struct kvm_memory_slot *slot)
{
if (kvm_memslot_flush_zap_all(kvm))
kvm_mmu_zap_all_fast(kvm);
else
kvm_mmu_zap_memslot(kvm, slot);
}
void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen)
{
WARN_ON_ONCE(gen & KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS);
gen &= MMIO_SPTE_GEN_MASK;
/*
* Generation numbers are incremented in multiples of the number of
* address spaces in order to provide unique generations across all
* address spaces. Strip what is effectively the address space
* modifier prior to checking for a wrap of the MMIO generation so
* that a wrap in any address space is detected.
*/
gen &= ~((u64)kvm_arch_nr_memslot_as_ids(kvm) - 1);
/*
* The very rare case: if the MMIO generation number has wrapped,
* zap all shadow pages.
*/
if (unlikely(gen == 0)) {
kvm_debug_ratelimited("zapping shadow pages for mmio generation wraparound\n");
kvm_mmu_zap_all_fast(kvm);
}
}
static unsigned long mmu_shrink_scan(struct shrinker *shrink,
struct shrink_control *sc)
{
struct kvm *kvm;
int nr_to_scan = sc->nr_to_scan;
unsigned long freed = 0;
mutex_lock(&kvm_lock);
list_for_each_entry(kvm, &vm_list, vm_list) {
int idx;
/*
* Never scan more than sc->nr_to_scan VM instances.
* Will not hit this condition practically since we do not try
* to shrink more than one VM and it is very unlikely to see
* !n_used_mmu_pages so many times.
*/
if (!nr_to_scan--)
break;
/*
* n_used_mmu_pages is accessed without holding kvm->mmu_lock
* here. We may skip a VM instance errorneosly, but we do not
* want to shrink a VM that only started to populate its MMU
* anyway.
*/
if (!kvm->arch.n_used_mmu_pages &&
!kvm_has_zapped_obsolete_pages(kvm))
continue;
idx = srcu_read_lock(&kvm->srcu);
write_lock(&kvm->mmu_lock);
if (kvm_has_zapped_obsolete_pages(kvm)) {
kvm_mmu_commit_zap_page(kvm,
&kvm->arch.zapped_obsolete_pages);
goto unlock;
}
freed = kvm_mmu_zap_oldest_mmu_pages(kvm, sc->nr_to_scan);
unlock:
write_unlock(&kvm->mmu_lock);
srcu_read_unlock(&kvm->srcu, idx);
/*
* unfair on small ones
* per-vm shrinkers cry out
* sadness comes quickly
*/
list_move_tail(&kvm->vm_list, &vm_list);
break;
}
mutex_unlock(&kvm_lock);
return freed;
}
static unsigned long mmu_shrink_count(struct shrinker *shrink,
struct shrink_control *sc)
{
return percpu_counter_read_positive(&kvm_total_used_mmu_pages);
}
static struct shrinker *mmu_shrinker;
static void mmu_destroy_caches(void)
{
kmem_cache_destroy(pte_list_desc_cache);
kmem_cache_destroy(mmu_page_header_cache);
}
static int get_nx_huge_pages(char *buffer, const struct kernel_param *kp)
{
if (nx_hugepage_mitigation_hard_disabled)
return sysfs_emit(buffer, "never\n");
return param_get_bool(buffer, kp);
}
static bool get_nx_auto_mode(void)
{
/* Return true when CPU has the bug, and mitigations are ON */
return boot_cpu_has_bug(X86_BUG_ITLB_MULTIHIT) && !cpu_mitigations_off();
}
static void __set_nx_huge_pages(bool val)
{
nx_huge_pages = itlb_multihit_kvm_mitigation = val;
}
static int set_nx_huge_pages(const char *val, const struct kernel_param *kp)
{
bool old_val = nx_huge_pages;
bool new_val;
if (nx_hugepage_mitigation_hard_disabled)
return -EPERM;
/* In "auto" mode deploy workaround only if CPU has the bug. */
if (sysfs_streq(val, "off")) {
new_val = 0;
} else if (sysfs_streq(val, "force")) {
new_val = 1;
} else if (sysfs_streq(val, "auto")) {
new_val = get_nx_auto_mode();
} else if (sysfs_streq(val, "never")) {
new_val = 0;
mutex_lock(&kvm_lock);
if (!list_empty(&vm_list)) {
mutex_unlock(&kvm_lock);
return -EBUSY;
}
nx_hugepage_mitigation_hard_disabled = true;
mutex_unlock(&kvm_lock);
} else if (kstrtobool(val, &new_val) < 0) {
return -EINVAL;
}
__set_nx_huge_pages(new_val);
if (new_val != old_val) {
struct kvm *kvm;
mutex_lock(&kvm_lock);
list_for_each_entry(kvm, &vm_list, vm_list) {
mutex_lock(&kvm->slots_lock);
kvm_mmu_zap_all_fast(kvm);
mutex_unlock(&kvm->slots_lock);
wake_up_process(kvm->arch.nx_huge_page_recovery_thread);
}
mutex_unlock(&kvm_lock);
}
return 0;
}
/*
* nx_huge_pages needs to be resolved to true/false when kvm.ko is loaded, as
* its default value of -1 is technically undefined behavior for a boolean.
* Forward the module init call to SPTE code so that it too can handle module
* params that need to be resolved/snapshot.
*/
void __init kvm_mmu_x86_module_init(void)
{
if (nx_huge_pages == -1)
__set_nx_huge_pages(get_nx_auto_mode());
/*
* Snapshot userspace's desire to enable the TDP MMU. Whether or not the
* TDP MMU is actually enabled is determined in kvm_configure_mmu()
* when the vendor module is loaded.
*/
tdp_mmu_allowed = tdp_mmu_enabled;
kvm_mmu_spte_module_init();
}
/*
* The bulk of the MMU initialization is deferred until the vendor module is
* loaded as many of the masks/values may be modified by VMX or SVM, i.e. need
* to be reset when a potentially different vendor module is loaded.
*/
int kvm_mmu_vendor_module_init(void)
{
int ret = -ENOMEM;
/*
* MMU roles use union aliasing which is, generally speaking, an
* undefined behavior. However, we supposedly know how compilers behave
* and the current status quo is unlikely to change. Guardians below are
* supposed to let us know if the assumption becomes false.
*/
BUILD_BUG_ON(sizeof(union kvm_mmu_page_role) != sizeof(u32));
BUILD_BUG_ON(sizeof(union kvm_mmu_extended_role) != sizeof(u32));
BUILD_BUG_ON(sizeof(union kvm_cpu_role) != sizeof(u64));
kvm_mmu_reset_all_pte_masks();
pte_list_desc_cache = KMEM_CACHE(pte_list_desc, SLAB_ACCOUNT);
if (!pte_list_desc_cache)
goto out;
mmu_page_header_cache = kmem_cache_create("kvm_mmu_page_header",
sizeof(struct kvm_mmu_page),
0, SLAB_ACCOUNT, NULL);
if (!mmu_page_header_cache)
goto out;
if (percpu_counter_init(&kvm_total_used_mmu_pages, 0, GFP_KERNEL))
goto out;
mmu_shrinker = shrinker_alloc(0, "x86-mmu");
if (!mmu_shrinker)
goto out_shrinker;
mmu_shrinker->count_objects = mmu_shrink_count;
mmu_shrinker->scan_objects = mmu_shrink_scan;
mmu_shrinker->seeks = DEFAULT_SEEKS * 10;
shrinker_register(mmu_shrinker);
return 0;
out_shrinker:
percpu_counter_destroy(&kvm_total_used_mmu_pages);
out:
mmu_destroy_caches();
return ret;
}
void kvm_mmu_destroy(struct kvm_vcpu *vcpu)
{
kvm_mmu_unload(vcpu);
free_mmu_pages(&vcpu->arch.root_mmu);
free_mmu_pages(&vcpu->arch.guest_mmu);
mmu_free_memory_caches(vcpu);
}
void kvm_mmu_vendor_module_exit(void)
{
mmu_destroy_caches();
percpu_counter_destroy(&kvm_total_used_mmu_pages);
shrinker_free(mmu_shrinker);
}
/*
* Calculate the effective recovery period, accounting for '0' meaning "let KVM
* select a halving time of 1 hour". Returns true if recovery is enabled.
*/
static bool calc_nx_huge_pages_recovery_period(uint *period)
{
/*
* Use READ_ONCE to get the params, this may be called outside of the
* param setters, e.g. by the kthread to compute its next timeout.
*/
bool enabled = READ_ONCE(nx_huge_pages);
uint ratio = READ_ONCE(nx_huge_pages_recovery_ratio);
if (!enabled || !ratio)
return false;
*period = READ_ONCE(nx_huge_pages_recovery_period_ms);
if (!*period) {
/* Make sure the period is not less than one second. */
ratio = min(ratio, 3600u);
*period = 60 * 60 * 1000 / ratio;
}
return true;
}
static int set_nx_huge_pages_recovery_param(const char *val, const struct kernel_param *kp)
{
bool was_recovery_enabled, is_recovery_enabled;
uint old_period, new_period;
int err;
if (nx_hugepage_mitigation_hard_disabled)
return -EPERM;
was_recovery_enabled = calc_nx_huge_pages_recovery_period(&old_period);
err = param_set_uint(val, kp);
if (err)
return err;
is_recovery_enabled = calc_nx_huge_pages_recovery_period(&new_period);
if (is_recovery_enabled &&
(!was_recovery_enabled || old_period > new_period)) {
struct kvm *kvm;
mutex_lock(&kvm_lock);
list_for_each_entry(kvm, &vm_list, vm_list)
wake_up_process(kvm->arch.nx_huge_page_recovery_thread);
mutex_unlock(&kvm_lock);
}
return err;
}
static void kvm_recover_nx_huge_pages(struct kvm *kvm)
{
unsigned long nx_lpage_splits = kvm->stat.nx_lpage_splits;
struct kvm_memory_slot *slot;
int rcu_idx;
struct kvm_mmu_page *sp;
unsigned int ratio;
LIST_HEAD(invalid_list);
bool flush = false;
ulong to_zap;
rcu_idx = srcu_read_lock(&kvm->srcu);
write_lock(&kvm->mmu_lock);
/*
* Zapping TDP MMU shadow pages, including the remote TLB flush, must
* be done under RCU protection, because the pages are freed via RCU
* callback.
*/
rcu_read_lock();
ratio = READ_ONCE(nx_huge_pages_recovery_ratio);
to_zap = ratio ? DIV_ROUND_UP(nx_lpage_splits, ratio) : 0;
for ( ; to_zap; --to_zap) {
if (list_empty(&kvm->arch.possible_nx_huge_pages))
break;
/*
* We use a separate list instead of just using active_mmu_pages
* because the number of shadow pages that be replaced with an
* NX huge page is expected to be relatively small compared to
* the total number of shadow pages. And because the TDP MMU
* doesn't use active_mmu_pages.
*/
sp = list_first_entry(&kvm->arch.possible_nx_huge_pages,
struct kvm_mmu_page,
possible_nx_huge_page_link);
WARN_ON_ONCE(!sp->nx_huge_page_disallowed);
WARN_ON_ONCE(!sp->role.direct);
/*
* Unaccount and do not attempt to recover any NX Huge Pages
* that are being dirty tracked, as they would just be faulted
* back in as 4KiB pages. The NX Huge Pages in this slot will be
* recovered, along with all the other huge pages in the slot,
* when dirty logging is disabled.
*
* Since gfn_to_memslot() is relatively expensive, it helps to
* skip it if it the test cannot possibly return true. On the
* other hand, if any memslot has logging enabled, chances are
* good that all of them do, in which case unaccount_nx_huge_page()
* is much cheaper than zapping the page.
*
* If a memslot update is in progress, reading an incorrect value
* of kvm->nr_memslots_dirty_logging is not a problem: if it is
* becoming zero, gfn_to_memslot() will be done unnecessarily; if
* it is becoming nonzero, the page will be zapped unnecessarily.
* Either way, this only affects efficiency in racy situations,
* and not correctness.
*/
slot = NULL;
if (atomic_read(&kvm->nr_memslots_dirty_logging)) {
struct kvm_memslots *slots;
slots = kvm_memslots_for_spte_role(kvm, sp->role);
slot = __gfn_to_memslot(slots, sp->gfn);
WARN_ON_ONCE(!slot);
}
if (slot && kvm_slot_dirty_track_enabled(slot))
unaccount_nx_huge_page(kvm, sp);
else if (is_tdp_mmu_page(sp))
flush |= kvm_tdp_mmu_zap_sp(kvm, sp);
else
kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
WARN_ON_ONCE(sp->nx_huge_page_disallowed);
if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) {
kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush);
rcu_read_unlock();
cond_resched_rwlock_write(&kvm->mmu_lock);
flush = false;
rcu_read_lock();
}
}
kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush);
rcu_read_unlock();
write_unlock(&kvm->mmu_lock);
srcu_read_unlock(&kvm->srcu, rcu_idx);
}
static long get_nx_huge_page_recovery_timeout(u64 start_time)
{
bool enabled;
uint period;
enabled = calc_nx_huge_pages_recovery_period(&period);
return enabled ? start_time + msecs_to_jiffies(period) - get_jiffies_64()
: MAX_SCHEDULE_TIMEOUT;
}
static int kvm_nx_huge_page_recovery_worker(struct kvm *kvm, uintptr_t data)
{
u64 start_time;
long remaining_time;
while (true) {
start_time = get_jiffies_64();
remaining_time = get_nx_huge_page_recovery_timeout(start_time);
set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop() && remaining_time > 0) {
schedule_timeout(remaining_time);
remaining_time = get_nx_huge_page_recovery_timeout(start_time);
set_current_state(TASK_INTERRUPTIBLE);
}
set_current_state(TASK_RUNNING);
if (kthread_should_stop())
return 0;
kvm_recover_nx_huge_pages(kvm);
}
}
int kvm_mmu_post_init_vm(struct kvm *kvm)
{
int err;
if (nx_hugepage_mitigation_hard_disabled)
return 0;
err = kvm_vm_create_worker_thread(kvm, kvm_nx_huge_page_recovery_worker, 0,
"kvm-nx-lpage-recovery",
&kvm->arch.nx_huge_page_recovery_thread);
if (!err)
kthread_unpark(kvm->arch.nx_huge_page_recovery_thread);
return err;
}
void kvm_mmu_pre_destroy_vm(struct kvm *kvm)
{
if (kvm->arch.nx_huge_page_recovery_thread)
kthread_stop(kvm->arch.nx_huge_page_recovery_thread);
}
#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
struct kvm_gfn_range *range)
{
/*
* Zap SPTEs even if the slot can't be mapped PRIVATE. KVM x86 only
* supports KVM_MEMORY_ATTRIBUTE_PRIVATE, and so it *seems* like KVM
* can simply ignore such slots. But if userspace is making memory
* PRIVATE, then KVM must prevent the guest from accessing the memory
* as shared. And if userspace is making memory SHARED and this point
* is reached, then at least one page within the range was previously
* PRIVATE, i.e. the slot's possible hugepage ranges are changing.
* Zapping SPTEs in this case ensures KVM will reassess whether or not
* a hugepage can be used for affected ranges.
*/
if (WARN_ON_ONCE(!kvm_arch_has_private_mem(kvm)))
return false;
return kvm_unmap_gfn_range(kvm, range);
}
static bool hugepage_test_mixed(struct kvm_memory_slot *slot, gfn_t gfn,
int level)
{
return lpage_info_slot(gfn, slot, level)->disallow_lpage & KVM_LPAGE_MIXED_FLAG;
}
static void hugepage_clear_mixed(struct kvm_memory_slot *slot, gfn_t gfn,
int level)
{
lpage_info_slot(gfn, slot, level)->disallow_lpage &= ~KVM_LPAGE_MIXED_FLAG;
}
static void hugepage_set_mixed(struct kvm_memory_slot *slot, gfn_t gfn,
int level)
{
lpage_info_slot(gfn, slot, level)->disallow_lpage |= KVM_LPAGE_MIXED_FLAG;
}
static bool hugepage_has_attrs(struct kvm *kvm, struct kvm_memory_slot *slot,
gfn_t gfn, int level, unsigned long attrs)
{
const unsigned long start = gfn;
const unsigned long end = start + KVM_PAGES_PER_HPAGE(level);
if (level == PG_LEVEL_2M)
return kvm_range_has_memory_attributes(kvm, start, end, ~0, attrs);
for (gfn = start; gfn < end; gfn += KVM_PAGES_PER_HPAGE(level - 1)) {
if (hugepage_test_mixed(slot, gfn, level - 1) ||
attrs != kvm_get_memory_attributes(kvm, gfn))
return false;
}
return true;
}
bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
struct kvm_gfn_range *range)
{
unsigned long attrs = range->arg.attributes;
struct kvm_memory_slot *slot = range->slot;
int level;
lockdep_assert_held_write(&kvm->mmu_lock);
lockdep_assert_held(&kvm->slots_lock);
/*
* Calculate which ranges can be mapped with hugepages even if the slot
* can't map memory PRIVATE. KVM mustn't create a SHARED hugepage over
* a range that has PRIVATE GFNs, and conversely converting a range to
* SHARED may now allow hugepages.
*/
if (WARN_ON_ONCE(!kvm_arch_has_private_mem(kvm)))
return false;
/*
* The sequence matters here: upper levels consume the result of lower
* level's scanning.
*/
for (level = PG_LEVEL_2M; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) {
gfn_t nr_pages = KVM_PAGES_PER_HPAGE(level);
gfn_t gfn = gfn_round_for_level(range->start, level);
/* Process the head page if it straddles the range. */
if (gfn != range->start || gfn + nr_pages > range->end) {
/*
* Skip mixed tracking if the aligned gfn isn't covered
* by the memslot, KVM can't use a hugepage due to the
* misaligned address regardless of memory attributes.
*/
if (gfn >= slot->base_gfn &&
gfn + nr_pages <= slot->base_gfn + slot->npages) {
if (hugepage_has_attrs(kvm, slot, gfn, level, attrs))
hugepage_clear_mixed(slot, gfn, level);
else
hugepage_set_mixed(slot, gfn, level);
}
gfn += nr_pages;
}
/*
* Pages entirely covered by the range are guaranteed to have
* only the attributes which were just set.
*/
for ( ; gfn + nr_pages <= range->end; gfn += nr_pages)
hugepage_clear_mixed(slot, gfn, level);
/*
* Process the last tail page if it straddles the range and is
* contained by the memslot. Like the head page, KVM can't
* create a hugepage if the slot size is misaligned.
*/
if (gfn < range->end &&
(gfn + nr_pages) <= (slot->base_gfn + slot->npages)) {
if (hugepage_has_attrs(kvm, slot, gfn, level, attrs))
hugepage_clear_mixed(slot, gfn, level);
else
hugepage_set_mixed(slot, gfn, level);
}
}
return false;
}
void kvm_mmu_init_memslot_memory_attributes(struct kvm *kvm,
struct kvm_memory_slot *slot)
{
int level;
if (!kvm_arch_has_private_mem(kvm))
return;
for (level = PG_LEVEL_2M; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) {
/*
* Don't bother tracking mixed attributes for pages that can't
* be huge due to alignment, i.e. process only pages that are
* entirely contained by the memslot.
*/
gfn_t end = gfn_round_for_level(slot->base_gfn + slot->npages, level);
gfn_t start = gfn_round_for_level(slot->base_gfn, level);
gfn_t nr_pages = KVM_PAGES_PER_HPAGE(level);
gfn_t gfn;
if (start < slot->base_gfn)
start += nr_pages;
/*
* Unlike setting attributes, every potential hugepage needs to
* be manually checked as the attributes may already be mixed.
*/
for (gfn = start; gfn < end; gfn += nr_pages) {
unsigned long attrs = kvm_get_memory_attributes(kvm, gfn);
if (hugepage_has_attrs(kvm, slot, gfn, level, attrs))
hugepage_clear_mixed(slot, gfn, level);
else
hugepage_set_mixed(slot, gfn, level);
}
}
}
#endif