blob: ec71846d28c9ed1230fc910954974aca73e51fcf [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
/*
* AMD Encrypted Register State Support
*
* Author: Joerg Roedel <jroedel@suse.de>
*/
/*
* misc.h needs to be first because it knows how to include the other kernel
* headers in the pre-decompression code in a way that does not break
* compilation.
*/
#include "misc.h"
#include <asm/bootparam.h>
#include <asm/pgtable_types.h>
#include <asm/sev.h>
#include <asm/trapnr.h>
#include <asm/trap_pf.h>
#include <asm/msr-index.h>
#include <asm/fpu/xcr.h>
#include <asm/ptrace.h>
#include <asm/svm.h>
#include <asm/cpuid.h>
#include "error.h"
#include "../msr.h"
static struct ghcb boot_ghcb_page __aligned(PAGE_SIZE);
struct ghcb *boot_ghcb;
/*
* Copy a version of this function here - insn-eval.c can't be used in
* pre-decompression code.
*/
static bool insn_has_rep_prefix(struct insn *insn)
{
insn_byte_t p;
int i;
insn_get_prefixes(insn);
for_each_insn_prefix(insn, i, p) {
if (p == 0xf2 || p == 0xf3)
return true;
}
return false;
}
/*
* Only a dummy for insn_get_seg_base() - Early boot-code is 64bit only and
* doesn't use segments.
*/
static unsigned long insn_get_seg_base(struct pt_regs *regs, int seg_reg_idx)
{
return 0UL;
}
static inline u64 sev_es_rd_ghcb_msr(void)
{
struct msr m;
boot_rdmsr(MSR_AMD64_SEV_ES_GHCB, &m);
return m.q;
}
static inline void sev_es_wr_ghcb_msr(u64 val)
{
struct msr m;
m.q = val;
boot_wrmsr(MSR_AMD64_SEV_ES_GHCB, &m);
}
static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt)
{
char buffer[MAX_INSN_SIZE];
int ret;
memcpy(buffer, (unsigned char *)ctxt->regs->ip, MAX_INSN_SIZE);
ret = insn_decode(&ctxt->insn, buffer, MAX_INSN_SIZE, INSN_MODE_64);
if (ret < 0)
return ES_DECODE_FAILED;
return ES_OK;
}
static enum es_result vc_write_mem(struct es_em_ctxt *ctxt,
void *dst, char *buf, size_t size)
{
memcpy(dst, buf, size);
return ES_OK;
}
static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
void *src, char *buf, size_t size)
{
memcpy(buf, src, size);
return ES_OK;
}
static enum es_result vc_ioio_check(struct es_em_ctxt *ctxt, u16 port, size_t size)
{
return ES_OK;
}
static bool fault_in_kernel_space(unsigned long address)
{
return false;
}
#undef __init
#define __init
#undef __head
#define __head
#define __BOOT_COMPRESSED
/* Basic instruction decoding support needed */
#include "../../lib/inat.c"
#include "../../lib/insn.c"
/* Include code for early handlers */
#include "../../kernel/sev-shared.c"
bool sev_snp_enabled(void)
{
return sev_status & MSR_AMD64_SEV_SNP_ENABLED;
}
static void __page_state_change(unsigned long paddr, enum psc_op op)
{
u64 val;
if (!sev_snp_enabled())
return;
/*
* If private -> shared then invalidate the page before requesting the
* state change in the RMP table.
*/
if (op == SNP_PAGE_STATE_SHARED && pvalidate(paddr, RMP_PG_SIZE_4K, 0))
sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PVALIDATE);
/* Issue VMGEXIT to change the page state in RMP table. */
sev_es_wr_ghcb_msr(GHCB_MSR_PSC_REQ_GFN(paddr >> PAGE_SHIFT, op));
VMGEXIT();
/* Read the response of the VMGEXIT. */
val = sev_es_rd_ghcb_msr();
if ((GHCB_RESP_CODE(val) != GHCB_MSR_PSC_RESP) || GHCB_MSR_PSC_RESP_VAL(val))
sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PSC);
/*
* Now that page state is changed in the RMP table, validate it so that it is
* consistent with the RMP entry.
*/
if (op == SNP_PAGE_STATE_PRIVATE && pvalidate(paddr, RMP_PG_SIZE_4K, 1))
sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PVALIDATE);
}
void snp_set_page_private(unsigned long paddr)
{
__page_state_change(paddr, SNP_PAGE_STATE_PRIVATE);
}
void snp_set_page_shared(unsigned long paddr)
{
__page_state_change(paddr, SNP_PAGE_STATE_SHARED);
}
static bool early_setup_ghcb(void)
{
if (set_page_decrypted((unsigned long)&boot_ghcb_page))
return false;
/* Page is now mapped decrypted, clear it */
memset(&boot_ghcb_page, 0, sizeof(boot_ghcb_page));
boot_ghcb = &boot_ghcb_page;
/* Initialize lookup tables for the instruction decoder */
inat_init_tables();
/* SNP guest requires the GHCB GPA must be registered */
if (sev_snp_enabled())
snp_register_ghcb_early(__pa(&boot_ghcb_page));
return true;
}
static phys_addr_t __snp_accept_memory(struct snp_psc_desc *desc,
phys_addr_t pa, phys_addr_t pa_end)
{
struct psc_hdr *hdr;
struct psc_entry *e;
unsigned int i;
hdr = &desc->hdr;
memset(hdr, 0, sizeof(*hdr));
e = desc->entries;
i = 0;
while (pa < pa_end && i < VMGEXIT_PSC_MAX_ENTRY) {
hdr->end_entry = i;
e->gfn = pa >> PAGE_SHIFT;
e->operation = SNP_PAGE_STATE_PRIVATE;
if (IS_ALIGNED(pa, PMD_SIZE) && (pa_end - pa) >= PMD_SIZE) {
e->pagesize = RMP_PG_SIZE_2M;
pa += PMD_SIZE;
} else {
e->pagesize = RMP_PG_SIZE_4K;
pa += PAGE_SIZE;
}
e++;
i++;
}
if (vmgexit_psc(boot_ghcb, desc))
sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PSC);
pvalidate_pages(desc);
return pa;
}
void snp_accept_memory(phys_addr_t start, phys_addr_t end)
{
struct snp_psc_desc desc = {};
unsigned int i;
phys_addr_t pa;
if (!boot_ghcb && !early_setup_ghcb())
sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PSC);
pa = start;
while (pa < end)
pa = __snp_accept_memory(&desc, pa, end);
}
void sev_es_shutdown_ghcb(void)
{
if (!boot_ghcb)
return;
if (!sev_es_check_cpu_features())
error("SEV-ES CPU Features missing.");
/*
* GHCB Page must be flushed from the cache and mapped encrypted again.
* Otherwise the running kernel will see strange cache effects when
* trying to use that page.
*/
if (set_page_encrypted((unsigned long)&boot_ghcb_page))
error("Can't map GHCB page encrypted");
/*
* GHCB page is mapped encrypted again and flushed from the cache.
* Mark it non-present now to catch bugs when #VC exceptions trigger
* after this point.
*/
if (set_page_non_present((unsigned long)&boot_ghcb_page))
error("Can't unmap GHCB page");
}
static void __noreturn sev_es_ghcb_terminate(struct ghcb *ghcb, unsigned int set,
unsigned int reason, u64 exit_info_2)
{
u64 exit_info_1 = SVM_VMGEXIT_TERM_REASON(set, reason);
vc_ghcb_invalidate(ghcb);
ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_TERM_REQUEST);
ghcb_set_sw_exit_info_1(ghcb, exit_info_1);
ghcb_set_sw_exit_info_2(ghcb, exit_info_2);
sev_es_wr_ghcb_msr(__pa(ghcb));
VMGEXIT();
while (true)
asm volatile("hlt\n" : : : "memory");
}
bool sev_es_check_ghcb_fault(unsigned long address)
{
/* Check whether the fault was on the GHCB page */
return ((address & PAGE_MASK) == (unsigned long)&boot_ghcb_page);
}
void do_boot_stage2_vc(struct pt_regs *regs, unsigned long exit_code)
{
struct es_em_ctxt ctxt;
enum es_result result;
if (!boot_ghcb && !early_setup_ghcb())
sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ);
vc_ghcb_invalidate(boot_ghcb);
result = vc_init_em_ctxt(&ctxt, regs, exit_code);
if (result != ES_OK)
goto finish;
result = vc_check_opcode_bytes(&ctxt, exit_code);
if (result != ES_OK)
goto finish;
switch (exit_code) {
case SVM_EXIT_RDTSC:
case SVM_EXIT_RDTSCP:
result = vc_handle_rdtsc(boot_ghcb, &ctxt, exit_code);
break;
case SVM_EXIT_IOIO:
result = vc_handle_ioio(boot_ghcb, &ctxt);
break;
case SVM_EXIT_CPUID:
result = vc_handle_cpuid(boot_ghcb, &ctxt);
break;
default:
result = ES_UNSUPPORTED;
break;
}
finish:
if (result == ES_OK)
vc_finish_insn(&ctxt);
else if (result != ES_RETRY)
sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ);
}
static void enforce_vmpl0(void)
{
u64 attrs;
int err;
/*
* RMPADJUST modifies RMP permissions of a lesser-privileged (numerically
* higher) privilege level. Here, clear the VMPL1 permission mask of the
* GHCB page. If the guest is not running at VMPL0, this will fail.
*
* If the guest is running at VMPL0, it will succeed. Even if that operation
* modifies permission bits, it is still ok to do so currently because Linux
* SNP guests are supported only on VMPL0 so VMPL1 or higher permission masks
* changing is a don't-care.
*/
attrs = 1;
if (rmpadjust((unsigned long)&boot_ghcb_page, RMP_PG_SIZE_4K, attrs))
sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_NOT_VMPL0);
}
/*
* SNP_FEATURES_IMPL_REQ is the mask of SNP features that will need
* guest side implementation for proper functioning of the guest. If any
* of these features are enabled in the hypervisor but are lacking guest
* side implementation, the behavior of the guest will be undefined. The
* guest could fail in non-obvious way making it difficult to debug.
*
* As the behavior of reserved feature bits is unknown to be on the
* safe side add them to the required features mask.
*/
#define SNP_FEATURES_IMPL_REQ (MSR_AMD64_SNP_VTOM | \
MSR_AMD64_SNP_REFLECT_VC | \
MSR_AMD64_SNP_RESTRICTED_INJ | \
MSR_AMD64_SNP_ALT_INJ | \
MSR_AMD64_SNP_DEBUG_SWAP | \
MSR_AMD64_SNP_VMPL_SSS | \
MSR_AMD64_SNP_SECURE_TSC | \
MSR_AMD64_SNP_VMGEXIT_PARAM | \
MSR_AMD64_SNP_VMSA_REG_PROT | \
MSR_AMD64_SNP_RESERVED_BIT13 | \
MSR_AMD64_SNP_RESERVED_BIT15 | \
MSR_AMD64_SNP_RESERVED_MASK)
/*
* SNP_FEATURES_PRESENT is the mask of SNP features that are implemented
* by the guest kernel. As and when a new feature is implemented in the
* guest kernel, a corresponding bit should be added to the mask.
*/
#define SNP_FEATURES_PRESENT MSR_AMD64_SNP_DEBUG_SWAP
u64 snp_get_unsupported_features(u64 status)
{
if (!(status & MSR_AMD64_SEV_SNP_ENABLED))
return 0;
return status & SNP_FEATURES_IMPL_REQ & ~SNP_FEATURES_PRESENT;
}
void snp_check_features(void)
{
u64 unsupported;
/*
* Terminate the boot if hypervisor has enabled any feature lacking
* guest side implementation. Pass on the unsupported features mask through
* EXIT_INFO_2 of the GHCB protocol so that those features can be reported
* as part of the guest boot failure.
*/
unsupported = snp_get_unsupported_features(sev_status);
if (unsupported) {
if (ghcb_version < 2 || (!boot_ghcb && !early_setup_ghcb()))
sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);
sev_es_ghcb_terminate(boot_ghcb, SEV_TERM_SET_GEN,
GHCB_SNP_UNSUPPORTED, unsupported);
}
}
/*
* sev_check_cpu_support - Check for SEV support in the CPU capabilities
*
* Returns < 0 if SEV is not supported, otherwise the position of the
* encryption bit in the page table descriptors.
*/
static int sev_check_cpu_support(void)
{
unsigned int eax, ebx, ecx, edx;
/* Check for the SME/SEV support leaf */
eax = 0x80000000;
ecx = 0;
native_cpuid(&eax, &ebx, &ecx, &edx);
if (eax < 0x8000001f)
return -ENODEV;
/*
* Check for the SME/SEV feature:
* CPUID Fn8000_001F[EAX]
* - Bit 0 - Secure Memory Encryption support
* - Bit 1 - Secure Encrypted Virtualization support
* CPUID Fn8000_001F[EBX]
* - Bits 5:0 - Pagetable bit position used to indicate encryption
*/
eax = 0x8000001f;
ecx = 0;
native_cpuid(&eax, &ebx, &ecx, &edx);
/* Check whether SEV is supported */
if (!(eax & BIT(1)))
return -ENODEV;
return ebx & 0x3f;
}
void sev_enable(struct boot_params *bp)
{
struct msr m;
int bitpos;
bool snp;
/*
* bp->cc_blob_address should only be set by boot/compressed kernel.
* Initialize it to 0 to ensure that uninitialized values from
* buggy bootloaders aren't propagated.
*/
if (bp)
bp->cc_blob_address = 0;
/*
* Do an initial SEV capability check before snp_init() which
* loads the CPUID page and the same checks afterwards are done
* without the hypervisor and are trustworthy.
*
* If the HV fakes SEV support, the guest will crash'n'burn
* which is good enough.
*/
if (sev_check_cpu_support() < 0)
return;
/*
* Setup/preliminary detection of SNP. This will be sanity-checked
* against CPUID/MSR values later.
*/
snp = snp_init(bp);
/* Now repeat the checks with the SNP CPUID table. */
bitpos = sev_check_cpu_support();
if (bitpos < 0) {
if (snp)
error("SEV-SNP support indicated by CC blob, but not CPUID.");
return;
}
/* Set the SME mask if this is an SEV guest. */
boot_rdmsr(MSR_AMD64_SEV, &m);
sev_status = m.q;
if (!(sev_status & MSR_AMD64_SEV_ENABLED))
return;
/* Negotiate the GHCB protocol version. */
if (sev_status & MSR_AMD64_SEV_ES_ENABLED) {
if (!sev_es_negotiate_protocol())
sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_PROT_UNSUPPORTED);
}
/*
* SNP is supported in v2 of the GHCB spec which mandates support for HV
* features.
*/
if (sev_status & MSR_AMD64_SEV_SNP_ENABLED) {
if (!(get_hv_features() & GHCB_HV_FT_SNP))
sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);
enforce_vmpl0();
}
if (snp && !(sev_status & MSR_AMD64_SEV_SNP_ENABLED))
error("SEV-SNP supported indicated by CC blob, but not SEV status MSR.");
sme_me_mask = BIT_ULL(bitpos);
}
/*
* sev_get_status - Retrieve the SEV status mask
*
* Returns 0 if the CPU is not SEV capable, otherwise the value of the
* AMD64_SEV MSR.
*/
u64 sev_get_status(void)
{
struct msr m;
if (sev_check_cpu_support() < 0)
return 0;
boot_rdmsr(MSR_AMD64_SEV, &m);
return m.q;
}
/* Search for Confidential Computing blob in the EFI config table. */
static struct cc_blob_sev_info *find_cc_blob_efi(struct boot_params *bp)
{
unsigned long cfg_table_pa;
unsigned int cfg_table_len;
int ret;
ret = efi_get_conf_table(bp, &cfg_table_pa, &cfg_table_len);
if (ret)
return NULL;
return (struct cc_blob_sev_info *)efi_find_vendor_table(bp, cfg_table_pa,
cfg_table_len,
EFI_CC_BLOB_GUID);
}
/*
* Initial set up of SNP relies on information provided by the
* Confidential Computing blob, which can be passed to the boot kernel
* by firmware/bootloader in the following ways:
*
* - via an entry in the EFI config table
* - via a setup_data structure, as defined by the Linux Boot Protocol
*
* Scan for the blob in that order.
*/
static struct cc_blob_sev_info *find_cc_blob(struct boot_params *bp)
{
struct cc_blob_sev_info *cc_info;
cc_info = find_cc_blob_efi(bp);
if (cc_info)
goto found_cc_info;
cc_info = find_cc_blob_setup_data(bp);
if (!cc_info)
return NULL;
found_cc_info:
if (cc_info->magic != CC_BLOB_SEV_HDR_MAGIC)
sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);
return cc_info;
}
/*
* Indicate SNP based on presence of SNP-specific CC blob. Subsequent checks
* will verify the SNP CPUID/MSR bits.
*/
bool snp_init(struct boot_params *bp)
{
struct cc_blob_sev_info *cc_info;
if (!bp)
return false;
cc_info = find_cc_blob(bp);
if (!cc_info)
return false;
/*
* If a SNP-specific Confidential Computing blob is present, then
* firmware/bootloader have indicated SNP support. Verifying this
* involves CPUID checks which will be more reliable if the SNP
* CPUID table is used. See comments over snp_setup_cpuid_table() for
* more details.
*/
setup_cpuid_table(cc_info);
/*
* Pass run-time kernel a pointer to CC info via boot_params so EFI
* config table doesn't need to be searched again during early startup
* phase.
*/
bp->cc_blob_address = (u32)(unsigned long)cc_info;
return true;
}
void sev_prep_identity_maps(unsigned long top_level_pgt)
{
/*
* The Confidential Computing blob is used very early in uncompressed
* kernel to find the in-memory CPUID table to handle CPUID
* instructions. Make sure an identity-mapping exists so it can be
* accessed after switchover.
*/
if (sev_snp_enabled()) {
unsigned long cc_info_pa = boot_params_ptr->cc_blob_address;
struct cc_blob_sev_info *cc_info;
kernel_add_identity_map(cc_info_pa, cc_info_pa + sizeof(*cc_info));
cc_info = (struct cc_blob_sev_info *)cc_info_pa;
kernel_add_identity_map(cc_info->cpuid_phys, cc_info->cpuid_phys + cc_info->cpuid_len);
}
sev_verify_cbit(top_level_pgt);
}