| /* |
| * KVM paravirt_ops implementation |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write to the Free Software |
| * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
| * |
| * Copyright (C) 2007, Red Hat, Inc., Ingo Molnar <mingo@redhat.com> |
| * Copyright IBM Corporation, 2007 |
| * Authors: Anthony Liguori <aliguori@us.ibm.com> |
| */ |
| |
| #include <linux/context_tracking.h> |
| #include <linux/module.h> |
| #include <linux/kernel.h> |
| #include <linux/kvm_para.h> |
| #include <linux/cpu.h> |
| #include <linux/mm.h> |
| #include <linux/highmem.h> |
| #include <linux/hardirq.h> |
| #include <linux/notifier.h> |
| #include <linux/reboot.h> |
| #include <linux/hash.h> |
| #include <linux/sched.h> |
| #include <linux/slab.h> |
| #include <linux/kprobes.h> |
| #include <linux/debugfs.h> |
| #include <linux/nmi.h> |
| #include <asm/timer.h> |
| #include <asm/cpu.h> |
| #include <asm/traps.h> |
| #include <asm/desc.h> |
| #include <asm/tlbflush.h> |
| #include <asm/idle.h> |
| #include <asm/apic.h> |
| #include <asm/apicdef.h> |
| #include <asm/hypervisor.h> |
| #include <asm/kvm_guest.h> |
| |
| static int kvmapf = 1; |
| |
| static int parse_no_kvmapf(char *arg) |
| { |
| kvmapf = 0; |
| return 0; |
| } |
| |
| early_param("no-kvmapf", parse_no_kvmapf); |
| |
| static int steal_acc = 1; |
| static int parse_no_stealacc(char *arg) |
| { |
| steal_acc = 0; |
| return 0; |
| } |
| |
| early_param("no-steal-acc", parse_no_stealacc); |
| |
| static int kvmclock_vsyscall = 1; |
| static int parse_no_kvmclock_vsyscall(char *arg) |
| { |
| kvmclock_vsyscall = 0; |
| return 0; |
| } |
| |
| early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall); |
| |
| static DEFINE_PER_CPU(struct kvm_vcpu_pv_apf_data, apf_reason) __aligned(64); |
| static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64); |
| static int has_steal_clock = 0; |
| |
| /* |
| * No need for any "IO delay" on KVM |
| */ |
| static void kvm_io_delay(void) |
| { |
| } |
| |
| #define KVM_TASK_SLEEP_HASHBITS 8 |
| #define KVM_TASK_SLEEP_HASHSIZE (1<<KVM_TASK_SLEEP_HASHBITS) |
| |
| struct kvm_task_sleep_node { |
| struct hlist_node link; |
| wait_queue_head_t wq; |
| u32 token; |
| int cpu; |
| bool halted; |
| }; |
| |
| static struct kvm_task_sleep_head { |
| spinlock_t lock; |
| struct hlist_head list; |
| } async_pf_sleepers[KVM_TASK_SLEEP_HASHSIZE]; |
| |
| static struct kvm_task_sleep_node *_find_apf_task(struct kvm_task_sleep_head *b, |
| u32 token) |
| { |
| struct hlist_node *p; |
| |
| hlist_for_each(p, &b->list) { |
| struct kvm_task_sleep_node *n = |
| hlist_entry(p, typeof(*n), link); |
| if (n->token == token) |
| return n; |
| } |
| |
| return NULL; |
| } |
| |
| void kvm_async_pf_task_wait(u32 token) |
| { |
| u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS); |
| struct kvm_task_sleep_head *b = &async_pf_sleepers[key]; |
| struct kvm_task_sleep_node n, *e; |
| DEFINE_WAIT(wait); |
| |
| rcu_irq_enter(); |
| |
| spin_lock(&b->lock); |
| e = _find_apf_task(b, token); |
| if (e) { |
| /* dummy entry exist -> wake up was delivered ahead of PF */ |
| hlist_del(&e->link); |
| kfree(e); |
| spin_unlock(&b->lock); |
| |
| rcu_irq_exit(); |
| return; |
| } |
| |
| n.token = token; |
| n.cpu = smp_processor_id(); |
| n.halted = is_idle_task(current) || preempt_count() > 1; |
| init_waitqueue_head(&n.wq); |
| hlist_add_head(&n.link, &b->list); |
| spin_unlock(&b->lock); |
| |
| for (;;) { |
| if (!n.halted) |
| prepare_to_wait(&n.wq, &wait, TASK_UNINTERRUPTIBLE); |
| if (hlist_unhashed(&n.link)) |
| break; |
| |
| if (!n.halted) { |
| local_irq_enable(); |
| schedule(); |
| local_irq_disable(); |
| } else { |
| /* |
| * We cannot reschedule. So halt. |
| */ |
| rcu_irq_exit(); |
| native_safe_halt(); |
| rcu_irq_enter(); |
| local_irq_disable(); |
| } |
| } |
| if (!n.halted) |
| finish_wait(&n.wq, &wait); |
| |
| rcu_irq_exit(); |
| return; |
| } |
| EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait); |
| |
| static void apf_task_wake_one(struct kvm_task_sleep_node *n) |
| { |
| hlist_del_init(&n->link); |
| if (n->halted) |
| smp_send_reschedule(n->cpu); |
| else if (waitqueue_active(&n->wq)) |
| wake_up(&n->wq); |
| } |
| |
| static void apf_task_wake_all(void) |
| { |
| int i; |
| |
| for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) { |
| struct hlist_node *p, *next; |
| struct kvm_task_sleep_head *b = &async_pf_sleepers[i]; |
| spin_lock(&b->lock); |
| hlist_for_each_safe(p, next, &b->list) { |
| struct kvm_task_sleep_node *n = |
| hlist_entry(p, typeof(*n), link); |
| if (n->cpu == smp_processor_id()) |
| apf_task_wake_one(n); |
| } |
| spin_unlock(&b->lock); |
| } |
| } |
| |
| void kvm_async_pf_task_wake(u32 token) |
| { |
| u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS); |
| struct kvm_task_sleep_head *b = &async_pf_sleepers[key]; |
| struct kvm_task_sleep_node *n; |
| |
| if (token == ~0) { |
| apf_task_wake_all(); |
| return; |
| } |
| |
| again: |
| spin_lock(&b->lock); |
| n = _find_apf_task(b, token); |
| if (!n) { |
| /* |
| * async PF was not yet handled. |
| * Add dummy entry for the token. |
| */ |
| n = kzalloc(sizeof(*n), GFP_ATOMIC); |
| if (!n) { |
| /* |
| * Allocation failed! Busy wait while other cpu |
| * handles async PF. |
| */ |
| spin_unlock(&b->lock); |
| cpu_relax(); |
| goto again; |
| } |
| n->token = token; |
| n->cpu = smp_processor_id(); |
| init_waitqueue_head(&n->wq); |
| hlist_add_head(&n->link, &b->list); |
| } else |
| apf_task_wake_one(n); |
| spin_unlock(&b->lock); |
| return; |
| } |
| EXPORT_SYMBOL_GPL(kvm_async_pf_task_wake); |
| |
| u32 kvm_read_and_reset_pf_reason(void) |
| { |
| u32 reason = 0; |
| |
| if (__this_cpu_read(apf_reason.enabled)) { |
| reason = __this_cpu_read(apf_reason.reason); |
| __this_cpu_write(apf_reason.reason, 0); |
| } |
| |
| return reason; |
| } |
| EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason); |
| NOKPROBE_SYMBOL(kvm_read_and_reset_pf_reason); |
| |
| dotraplinkage void |
| do_async_page_fault(struct pt_regs *regs, unsigned long error_code) |
| { |
| enum ctx_state prev_state; |
| |
| switch (kvm_read_and_reset_pf_reason()) { |
| default: |
| trace_do_page_fault(regs, error_code); |
| break; |
| case KVM_PV_REASON_PAGE_NOT_PRESENT: |
| /* page is swapped out by the host. */ |
| prev_state = exception_enter(); |
| exit_idle(); |
| kvm_async_pf_task_wait((u32)read_cr2()); |
| exception_exit(prev_state); |
| break; |
| case KVM_PV_REASON_PAGE_READY: |
| rcu_irq_enter(); |
| exit_idle(); |
| kvm_async_pf_task_wake((u32)read_cr2()); |
| rcu_irq_exit(); |
| break; |
| } |
| } |
| NOKPROBE_SYMBOL(do_async_page_fault); |
| |
| static void __init paravirt_ops_setup(void) |
| { |
| pv_info.name = "KVM"; |
| pv_info.paravirt_enabled = 1; |
| |
| if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY)) |
| pv_cpu_ops.io_delay = kvm_io_delay; |
| |
| #ifdef CONFIG_X86_IO_APIC |
| no_timer_check = 1; |
| #endif |
| } |
| |
| static void kvm_register_steal_time(void) |
| { |
| int cpu = smp_processor_id(); |
| struct kvm_steal_time *st = &per_cpu(steal_time, cpu); |
| |
| if (!has_steal_clock) |
| return; |
| |
| memset(st, 0, sizeof(*st)); |
| |
| wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED)); |
| pr_info("kvm-stealtime: cpu %d, msr %llx\n", |
| cpu, (unsigned long long) slow_virt_to_phys(st)); |
| } |
| |
| static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED; |
| |
| static void kvm_guest_apic_eoi_write(u32 reg, u32 val) |
| { |
| /** |
| * This relies on __test_and_clear_bit to modify the memory |
| * in a way that is atomic with respect to the local CPU. |
| * The hypervisor only accesses this memory from the local CPU so |
| * there's no need for lock or memory barriers. |
| * An optimization barrier is implied in apic write. |
| */ |
| if (__test_and_clear_bit(KVM_PV_EOI_BIT, this_cpu_ptr(&kvm_apic_eoi))) |
| return; |
| apic_write(APIC_EOI, APIC_EOI_ACK); |
| } |
| |
| void kvm_guest_cpu_init(void) |
| { |
| if (!kvm_para_available()) |
| return; |
| |
| if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) { |
| u64 pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason)); |
| |
| #ifdef CONFIG_PREEMPT |
| pa |= KVM_ASYNC_PF_SEND_ALWAYS; |
| #endif |
| wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED); |
| __this_cpu_write(apf_reason.enabled, 1); |
| printk(KERN_INFO"KVM setup async PF for cpu %d\n", |
| smp_processor_id()); |
| } |
| |
| if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) { |
| unsigned long pa; |
| /* Size alignment is implied but just to make it explicit. */ |
| BUILD_BUG_ON(__alignof__(kvm_apic_eoi) < 4); |
| __this_cpu_write(kvm_apic_eoi, 0); |
| pa = slow_virt_to_phys(this_cpu_ptr(&kvm_apic_eoi)) |
| | KVM_MSR_ENABLED; |
| wrmsrl(MSR_KVM_PV_EOI_EN, pa); |
| } |
| |
| if (has_steal_clock) |
| kvm_register_steal_time(); |
| } |
| |
| static void kvm_pv_disable_apf(void) |
| { |
| if (!__this_cpu_read(apf_reason.enabled)) |
| return; |
| |
| wrmsrl(MSR_KVM_ASYNC_PF_EN, 0); |
| __this_cpu_write(apf_reason.enabled, 0); |
| |
| printk(KERN_INFO"Unregister pv shared memory for cpu %d\n", |
| smp_processor_id()); |
| } |
| |
| static void kvm_pv_guest_cpu_reboot(void *unused) |
| { |
| /* |
| * We disable PV EOI before we load a new kernel by kexec, |
| * since MSR_KVM_PV_EOI_EN stores a pointer into old kernel's memory. |
| * New kernel can re-enable when it boots. |
| */ |
| if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) |
| wrmsrl(MSR_KVM_PV_EOI_EN, 0); |
| kvm_pv_disable_apf(); |
| kvm_disable_steal_time(); |
| } |
| |
| static int kvm_pv_reboot_notify(struct notifier_block *nb, |
| unsigned long code, void *unused) |
| { |
| if (code == SYS_RESTART) |
| on_each_cpu(kvm_pv_guest_cpu_reboot, NULL, 1); |
| return NOTIFY_DONE; |
| } |
| |
| static struct notifier_block kvm_pv_reboot_nb = { |
| .notifier_call = kvm_pv_reboot_notify, |
| }; |
| |
| static u64 kvm_steal_clock(int cpu) |
| { |
| u64 steal; |
| struct kvm_steal_time *src; |
| int version; |
| |
| src = &per_cpu(steal_time, cpu); |
| do { |
| version = src->version; |
| rmb(); |
| steal = src->steal; |
| rmb(); |
| } while ((version & 1) || (version != src->version)); |
| |
| return steal; |
| } |
| |
| void kvm_disable_steal_time(void) |
| { |
| if (!has_steal_clock) |
| return; |
| |
| wrmsr(MSR_KVM_STEAL_TIME, 0, 0); |
| } |
| |
| #ifdef CONFIG_SMP |
| static void __init kvm_smp_prepare_boot_cpu(void) |
| { |
| kvm_guest_cpu_init(); |
| native_smp_prepare_boot_cpu(); |
| kvm_spinlock_init(); |
| } |
| |
| static void kvm_guest_cpu_online(void *dummy) |
| { |
| kvm_guest_cpu_init(); |
| } |
| |
| static void kvm_guest_cpu_offline(void *dummy) |
| { |
| kvm_disable_steal_time(); |
| if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) |
| wrmsrl(MSR_KVM_PV_EOI_EN, 0); |
| kvm_pv_disable_apf(); |
| apf_task_wake_all(); |
| } |
| |
| static int kvm_cpu_notify(struct notifier_block *self, unsigned long action, |
| void *hcpu) |
| { |
| int cpu = (unsigned long)hcpu; |
| switch (action) { |
| case CPU_ONLINE: |
| case CPU_DOWN_FAILED: |
| case CPU_ONLINE_FROZEN: |
| smp_call_function_single(cpu, kvm_guest_cpu_online, NULL, 0); |
| break; |
| case CPU_DOWN_PREPARE: |
| case CPU_DOWN_PREPARE_FROZEN: |
| smp_call_function_single(cpu, kvm_guest_cpu_offline, NULL, 1); |
| break; |
| default: |
| break; |
| } |
| return NOTIFY_OK; |
| } |
| |
| static struct notifier_block kvm_cpu_notifier = { |
| .notifier_call = kvm_cpu_notify, |
| }; |
| #endif |
| |
| static void __init kvm_apf_trap_init(void) |
| { |
| set_intr_gate(14, async_page_fault); |
| } |
| |
| void __init kvm_guest_init(void) |
| { |
| int i; |
| |
| if (!kvm_para_available()) |
| return; |
| |
| paravirt_ops_setup(); |
| register_reboot_notifier(&kvm_pv_reboot_nb); |
| for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) |
| spin_lock_init(&async_pf_sleepers[i].lock); |
| if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF)) |
| x86_init.irqs.trap_init = kvm_apf_trap_init; |
| |
| if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) { |
| has_steal_clock = 1; |
| pv_time_ops.steal_clock = kvm_steal_clock; |
| } |
| |
| if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) |
| apic_set_eoi_write(kvm_guest_apic_eoi_write); |
| |
| if (kvmclock_vsyscall) |
| kvm_setup_vsyscall_timeinfo(); |
| |
| #ifdef CONFIG_SMP |
| smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu; |
| register_cpu_notifier(&kvm_cpu_notifier); |
| #else |
| kvm_guest_cpu_init(); |
| #endif |
| |
| /* |
| * Hard lockup detection is enabled by default. Disable it, as guests |
| * can get false positives too easily, for example if the host is |
| * overcommitted. |
| */ |
| watchdog_enable_hardlockup_detector(false); |
| } |
| |
| static noinline uint32_t __kvm_cpuid_base(void) |
| { |
| if (boot_cpu_data.cpuid_level < 0) |
| return 0; /* So we don't blow up on old processors */ |
| |
| if (cpu_has_hypervisor) |
| return hypervisor_cpuid_base("KVMKVMKVM\0\0\0", 0); |
| |
| return 0; |
| } |
| |
| static inline uint32_t kvm_cpuid_base(void) |
| { |
| static int kvm_cpuid_base = -1; |
| |
| if (kvm_cpuid_base == -1) |
| kvm_cpuid_base = __kvm_cpuid_base(); |
| |
| return kvm_cpuid_base; |
| } |
| |
| bool kvm_para_available(void) |
| { |
| return kvm_cpuid_base() != 0; |
| } |
| EXPORT_SYMBOL_GPL(kvm_para_available); |
| |
| unsigned int kvm_arch_para_features(void) |
| { |
| return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_FEATURES); |
| } |
| |
| static uint32_t __init kvm_detect(void) |
| { |
| return kvm_cpuid_base(); |
| } |
| |
| const struct hypervisor_x86 x86_hyper_kvm __refconst = { |
| .name = "KVM", |
| .detect = kvm_detect, |
| .x2apic_available = kvm_para_available, |
| }; |
| EXPORT_SYMBOL_GPL(x86_hyper_kvm); |
| |
| static __init int activate_jump_labels(void) |
| { |
| if (has_steal_clock) { |
| static_key_slow_inc(¶virt_steal_enabled); |
| if (steal_acc) |
| static_key_slow_inc(¶virt_steal_rq_enabled); |
| } |
| |
| return 0; |
| } |
| arch_initcall(activate_jump_labels); |
| |
| #ifdef CONFIG_PARAVIRT_SPINLOCKS |
| |
| /* Kick a cpu by its apicid. Used to wake up a halted vcpu */ |
| static void kvm_kick_cpu(int cpu) |
| { |
| int apicid; |
| unsigned long flags = 0; |
| |
| apicid = per_cpu(x86_cpu_to_apicid, cpu); |
| kvm_hypercall2(KVM_HC_KICK_CPU, flags, apicid); |
| } |
| |
| enum kvm_contention_stat { |
| TAKEN_SLOW, |
| TAKEN_SLOW_PICKUP, |
| RELEASED_SLOW, |
| RELEASED_SLOW_KICKED, |
| NR_CONTENTION_STATS |
| }; |
| |
| #ifdef CONFIG_KVM_DEBUG_FS |
| #define HISTO_BUCKETS 30 |
| |
| static struct kvm_spinlock_stats |
| { |
| u32 contention_stats[NR_CONTENTION_STATS]; |
| u32 histo_spin_blocked[HISTO_BUCKETS+1]; |
| u64 time_blocked; |
| } spinlock_stats; |
| |
| static u8 zero_stats; |
| |
| static inline void check_zero(void) |
| { |
| u8 ret; |
| u8 old; |
| |
| old = ACCESS_ONCE(zero_stats); |
| if (unlikely(old)) { |
| ret = cmpxchg(&zero_stats, old, 0); |
| /* This ensures only one fellow resets the stat */ |
| if (ret == old) |
| memset(&spinlock_stats, 0, sizeof(spinlock_stats)); |
| } |
| } |
| |
| static inline void add_stats(enum kvm_contention_stat var, u32 val) |
| { |
| check_zero(); |
| spinlock_stats.contention_stats[var] += val; |
| } |
| |
| |
| static inline u64 spin_time_start(void) |
| { |
| return sched_clock(); |
| } |
| |
| static void __spin_time_accum(u64 delta, u32 *array) |
| { |
| unsigned index; |
| |
| index = ilog2(delta); |
| check_zero(); |
| |
| if (index < HISTO_BUCKETS) |
| array[index]++; |
| else |
| array[HISTO_BUCKETS]++; |
| } |
| |
| static inline void spin_time_accum_blocked(u64 start) |
| { |
| u32 delta; |
| |
| delta = sched_clock() - start; |
| __spin_time_accum(delta, spinlock_stats.histo_spin_blocked); |
| spinlock_stats.time_blocked += delta; |
| } |
| |
| static struct dentry *d_spin_debug; |
| static struct dentry *d_kvm_debug; |
| |
| struct dentry *kvm_init_debugfs(void) |
| { |
| d_kvm_debug = debugfs_create_dir("kvm-guest", NULL); |
| if (!d_kvm_debug) |
| printk(KERN_WARNING "Could not create 'kvm' debugfs directory\n"); |
| |
| return d_kvm_debug; |
| } |
| |
| static int __init kvm_spinlock_debugfs(void) |
| { |
| struct dentry *d_kvm; |
| |
| d_kvm = kvm_init_debugfs(); |
| if (d_kvm == NULL) |
| return -ENOMEM; |
| |
| d_spin_debug = debugfs_create_dir("spinlocks", d_kvm); |
| |
| debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats); |
| |
| debugfs_create_u32("taken_slow", 0444, d_spin_debug, |
| &spinlock_stats.contention_stats[TAKEN_SLOW]); |
| debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug, |
| &spinlock_stats.contention_stats[TAKEN_SLOW_PICKUP]); |
| |
| debugfs_create_u32("released_slow", 0444, d_spin_debug, |
| &spinlock_stats.contention_stats[RELEASED_SLOW]); |
| debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug, |
| &spinlock_stats.contention_stats[RELEASED_SLOW_KICKED]); |
| |
| debugfs_create_u64("time_blocked", 0444, d_spin_debug, |
| &spinlock_stats.time_blocked); |
| |
| debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug, |
| spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1); |
| |
| return 0; |
| } |
| fs_initcall(kvm_spinlock_debugfs); |
| #else /* !CONFIG_KVM_DEBUG_FS */ |
| static inline void add_stats(enum kvm_contention_stat var, u32 val) |
| { |
| } |
| |
| static inline u64 spin_time_start(void) |
| { |
| return 0; |
| } |
| |
| static inline void spin_time_accum_blocked(u64 start) |
| { |
| } |
| #endif /* CONFIG_KVM_DEBUG_FS */ |
| |
| struct kvm_lock_waiting { |
| struct arch_spinlock *lock; |
| __ticket_t want; |
| }; |
| |
| /* cpus 'waiting' on a spinlock to become available */ |
| static cpumask_t waiting_cpus; |
| |
| /* Track spinlock on which a cpu is waiting */ |
| static DEFINE_PER_CPU(struct kvm_lock_waiting, klock_waiting); |
| |
| __visible void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want) |
| { |
| struct kvm_lock_waiting *w; |
| int cpu; |
| u64 start; |
| unsigned long flags; |
| |
| if (in_nmi()) |
| return; |
| |
| w = this_cpu_ptr(&klock_waiting); |
| cpu = smp_processor_id(); |
| start = spin_time_start(); |
| |
| /* |
| * Make sure an interrupt handler can't upset things in a |
| * partially setup state. |
| */ |
| local_irq_save(flags); |
| |
| /* |
| * The ordering protocol on this is that the "lock" pointer |
| * may only be set non-NULL if the "want" ticket is correct. |
| * If we're updating "want", we must first clear "lock". |
| */ |
| w->lock = NULL; |
| smp_wmb(); |
| w->want = want; |
| smp_wmb(); |
| w->lock = lock; |
| |
| add_stats(TAKEN_SLOW, 1); |
| |
| /* |
| * This uses set_bit, which is atomic but we should not rely on its |
| * reordering gurantees. So barrier is needed after this call. |
| */ |
| cpumask_set_cpu(cpu, &waiting_cpus); |
| |
| barrier(); |
| |
| /* |
| * Mark entry to slowpath before doing the pickup test to make |
| * sure we don't deadlock with an unlocker. |
| */ |
| __ticket_enter_slowpath(lock); |
| |
| /* |
| * check again make sure it didn't become free while |
| * we weren't looking. |
| */ |
| if (ACCESS_ONCE(lock->tickets.head) == want) { |
| add_stats(TAKEN_SLOW_PICKUP, 1); |
| goto out; |
| } |
| |
| /* |
| * halt until it's our turn and kicked. Note that we do safe halt |
| * for irq enabled case to avoid hang when lock info is overwritten |
| * in irq spinlock slowpath and no spurious interrupt occur to save us. |
| */ |
| if (arch_irqs_disabled_flags(flags)) |
| halt(); |
| else |
| safe_halt(); |
| |
| out: |
| cpumask_clear_cpu(cpu, &waiting_cpus); |
| w->lock = NULL; |
| local_irq_restore(flags); |
| spin_time_accum_blocked(start); |
| } |
| PV_CALLEE_SAVE_REGS_THUNK(kvm_lock_spinning); |
| |
| /* Kick vcpu waiting on @lock->head to reach value @ticket */ |
| static void kvm_unlock_kick(struct arch_spinlock *lock, __ticket_t ticket) |
| { |
| int cpu; |
| |
| add_stats(RELEASED_SLOW, 1); |
| for_each_cpu(cpu, &waiting_cpus) { |
| const struct kvm_lock_waiting *w = &per_cpu(klock_waiting, cpu); |
| if (ACCESS_ONCE(w->lock) == lock && |
| ACCESS_ONCE(w->want) == ticket) { |
| add_stats(RELEASED_SLOW_KICKED, 1); |
| kvm_kick_cpu(cpu); |
| break; |
| } |
| } |
| } |
| |
| /* |
| * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present. |
| */ |
| void __init kvm_spinlock_init(void) |
| { |
| if (!kvm_para_available()) |
| return; |
| /* Does host kernel support KVM_FEATURE_PV_UNHALT? */ |
| if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT)) |
| return; |
| |
| pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning); |
| pv_lock_ops.unlock_kick = kvm_unlock_kick; |
| } |
| |
| static __init int kvm_spinlock_init_jump(void) |
| { |
| if (!kvm_para_available()) |
| return 0; |
| if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT)) |
| return 0; |
| |
| static_key_slow_inc(¶virt_ticketlocks_enabled); |
| printk(KERN_INFO "KVM setup paravirtual spinlock\n"); |
| |
| return 0; |
| } |
| early_initcall(kvm_spinlock_init_jump); |
| |
| #endif /* CONFIG_PARAVIRT_SPINLOCKS */ |