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Commit c8076604 authored by Gerd Hoffmann's avatar Gerd Hoffmann Committed by Avi Kivity
Browse files

KVM: Fix kvmclock on !constant_tsc boxes 



kvmclock currently falls apart on machines without constant tsc.
This patch fixes it.  Changes:

  * keep tsc frequency in a per-cpu variable.
  * handle kvmclock update using a new request flag, thus checking
    whenever we need an update each time we enter guest context.
  * use a cpufreq notifier to track frequency changes and force
    kvmclock updates.
  * send ipis to kick cpu out of guest context if needed to make
    sure the guest doesn't see stale values.

Signed-off-by: default avatarGerd Hoffmann <kraxel@redhat.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 49cd7d22

arch/x86/kvm/x86.c

+94 −9
Original line number Original line Diff line number Diff line
@@ -36,6 +36,7 @@ 
#include <linux/highmem.h>

#include <linux/highmem.h>

#include <linux/iommu.h>

#include <linux/iommu.h>

#include <linux/intel-iommu.h>

#include <linux/intel-iommu.h>

#include <linux/cpufreq.h>





#include <asm/uaccess.h>

#include <asm/uaccess.h>

#include <asm/msr.h>

#include <asm/msr.h>
@@ -617,6 +618,8 @@ static void kvm_set_time_scale(uint32_t tsc_khz, struct pvclock_vcpu_time_info * 
		 hv_clock->tsc_to_system_mul);

		 hv_clock->tsc_to_system_mul);

}

}





static DEFINE_PER_CPU(unsigned long, cpu_tsc_khz);



static void kvm_write_guest_time(struct kvm_vcpu *v)

static void kvm_write_guest_time(struct kvm_vcpu *v)

{

{

	struct timespec ts;

	struct timespec ts;
@@ -627,9 +630,9 @@ static void kvm_write_guest_time(struct kvm_vcpu *v) 
	if ((!vcpu->time_page))

	if ((!vcpu->time_page))

		return;

		return;





	if (unlikely(vcpu->hv_clock_tsc_khz != tsc_khz)) {

	if (unlikely(vcpu->hv_clock_tsc_khz != __get_cpu_var(cpu_tsc_khz))) {

		kvm_set_time_scale(tsc_khz, &vcpu->hv_clock);

		kvm_set_time_scale(__get_cpu_var(cpu_tsc_khz), &vcpu->hv_clock);

		vcpu->hv_clock_tsc_khz = tsc_khz;

		vcpu->hv_clock_tsc_khz = __get_cpu_var(cpu_tsc_khz);

	}

	}





	/* Keep irq disabled to prevent changes to the clock */

	/* Keep irq disabled to prevent changes to the clock */
@@ -660,6 +663,16 @@ static void kvm_write_guest_time(struct kvm_vcpu *v) 
	mark_page_dirty(v->kvm, vcpu->time >> PAGE_SHIFT);

	mark_page_dirty(v->kvm, vcpu->time >> PAGE_SHIFT);

}

}





static int kvm_request_guest_time_update(struct kvm_vcpu *v)

{

	struct kvm_vcpu_arch *vcpu = &v->arch;



	if (!vcpu->time_page)

		return 0;

	set_bit(KVM_REQ_KVMCLOCK_UPDATE, &v->requests);

	return 1;

}



static bool msr_mtrr_valid(unsigned msr)

static bool msr_mtrr_valid(unsigned msr)

{

{

	switch (msr) {

	switch (msr) {
@@ -790,7 +803,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data) 
			vcpu->arch.time_page = NULL;

			vcpu->arch.time_page = NULL;

		}

		}





		kvm_write_guest_time(vcpu);

		kvm_request_guest_time_update(vcpu);

		break;

		break;

	}

	}

	default:

	default:
@@ -1000,6 +1013,7 @@ int kvm_dev_ioctl_check_extension(long ext) 
	case KVM_CAP_MMU_SHADOW_CACHE_CONTROL:

	case KVM_CAP_MMU_SHADOW_CACHE_CONTROL:

	case KVM_CAP_SET_TSS_ADDR:

	case KVM_CAP_SET_TSS_ADDR:

	case KVM_CAP_EXT_CPUID:

	case KVM_CAP_EXT_CPUID:

	case KVM_CAP_CLOCKSOURCE:

	case KVM_CAP_PIT:

	case KVM_CAP_PIT:

	case KVM_CAP_NOP_IO_DELAY:

	case KVM_CAP_NOP_IO_DELAY:

	case KVM_CAP_MP_STATE:

	case KVM_CAP_MP_STATE:
@@ -1025,9 +1039,6 @@ int kvm_dev_ioctl_check_extension(long ext) 
	case KVM_CAP_IOMMU:

	case KVM_CAP_IOMMU:

		r = iommu_found();

		r = iommu_found();

		break;

		break;

	case KVM_CAP_CLOCKSOURCE:

		r = boot_cpu_has(X86_FEATURE_CONSTANT_TSC);

		break;

	default:

	default:

		r = 0;

		r = 0;

		break;

		break;
@@ -1098,7 +1109,7 @@ long kvm_arch_dev_ioctl(struct file *filp, 
void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)

void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)

{

{

	kvm_x86_ops->vcpu_load(vcpu, cpu);

	kvm_x86_ops->vcpu_load(vcpu, cpu);

	kvm_write_guest_time(vcpu);

	kvm_request_guest_time_update(vcpu);

}

}





void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)

void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
@@ -2642,9 +2653,72 @@ int kvm_emulate_pio_string(struct kvm_vcpu *vcpu, struct kvm_run *run, int in, 
}

}

EXPORT_SYMBOL_GPL(kvm_emulate_pio_string);

EXPORT_SYMBOL_GPL(kvm_emulate_pio_string);





static void bounce_off(void *info)

{

	/* nothing */

}



static unsigned int  ref_freq;

static unsigned long tsc_khz_ref;



static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long val,

				     void *data)

{

	struct cpufreq_freqs *freq = data;

	struct kvm *kvm;

	struct kvm_vcpu *vcpu;

	int i, send_ipi = 0;



	if (!ref_freq)

		ref_freq = freq->old;



	if (val == CPUFREQ_PRECHANGE && freq->old > freq->new)

		return 0;

	if (val == CPUFREQ_POSTCHANGE && freq->old < freq->new)

		return 0;

	per_cpu(cpu_tsc_khz, freq->cpu) = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new);



	spin_lock(&kvm_lock);

	list_for_each_entry(kvm, &vm_list, vm_list) {

		for (i = 0; i < KVM_MAX_VCPUS; ++i) {

			vcpu = kvm->vcpus[i];

			if (!vcpu)

				continue;

			if (vcpu->cpu != freq->cpu)

				continue;

			if (!kvm_request_guest_time_update(vcpu))

				continue;

			if (vcpu->cpu != smp_processor_id())

				send_ipi++;

		}

	}

	spin_unlock(&kvm_lock);



	if (freq->old < freq->new && send_ipi) {

		/*

		 * We upscale the frequency.  Must make the guest

		 * doesn't see old kvmclock values while running with

		 * the new frequency, otherwise we risk the guest sees

		 * time go backwards.

		 *

		 * In case we update the frequency for another cpu

		 * (which might be in guest context) send an interrupt

		 * to kick the cpu out of guest context.  Next time

		 * guest context is entered kvmclock will be updated,

		 * so the guest will not see stale values.

		 */

		smp_call_function_single(freq->cpu, bounce_off, NULL, 1);

	}

	return 0;

}



static struct notifier_block kvmclock_cpufreq_notifier_block = {

        .notifier_call  = kvmclock_cpufreq_notifier

};



int kvm_arch_init(void *opaque)

int kvm_arch_init(void *opaque)

{

{

	int r;

	int r, cpu;

	struct kvm_x86_ops *ops = (struct kvm_x86_ops *)opaque;

	struct kvm_x86_ops *ops = (struct kvm_x86_ops *)opaque;





	if (kvm_x86_ops) {

	if (kvm_x86_ops) {
@@ -2675,6 +2749,15 @@ int kvm_arch_init(void *opaque) 
	kvm_mmu_set_base_ptes(PT_PRESENT_MASK);

	kvm_mmu_set_base_ptes(PT_PRESENT_MASK);

	kvm_mmu_set_mask_ptes(PT_USER_MASK, PT_ACCESSED_MASK,

	kvm_mmu_set_mask_ptes(PT_USER_MASK, PT_ACCESSED_MASK,

			PT_DIRTY_MASK, PT64_NX_MASK, 0, 0);

			PT_DIRTY_MASK, PT64_NX_MASK, 0, 0);



	for_each_possible_cpu(cpu)

		per_cpu(cpu_tsc_khz, cpu) = tsc_khz;

	if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) {

		tsc_khz_ref = tsc_khz;

		cpufreq_register_notifier(&kvmclock_cpufreq_notifier_block,

					  CPUFREQ_TRANSITION_NOTIFIER);

	}



	return 0;

	return 0;





out:

out:
@@ -3010,6 +3093,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) 
	if (vcpu->requests) {

	if (vcpu->requests) {

		if (test_and_clear_bit(KVM_REQ_MIGRATE_TIMER, &vcpu->requests))

		if (test_and_clear_bit(KVM_REQ_MIGRATE_TIMER, &vcpu->requests))

			__kvm_migrate_timers(vcpu);

			__kvm_migrate_timers(vcpu);

		if (test_and_clear_bit(KVM_REQ_KVMCLOCK_UPDATE, &vcpu->requests))

			kvm_write_guest_time(vcpu);

		if (test_and_clear_bit(KVM_REQ_MMU_SYNC, &vcpu->requests))

		if (test_and_clear_bit(KVM_REQ_MMU_SYNC, &vcpu->requests))

			kvm_mmu_sync_roots(vcpu);

			kvm_mmu_sync_roots(vcpu);

		if (test_and_clear_bit(KVM_REQ_TLB_FLUSH, &vcpu->requests))

		if (test_and_clear_bit(KVM_REQ_TLB_FLUSH, &vcpu->requests))

include/linux/kvm_host.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -37,6 +37,7 @@ 
#define KVM_REQ_PENDING_TIMER      5

#define KVM_REQ_PENDING_TIMER      5

#define KVM_REQ_UNHALT             6

#define KVM_REQ_UNHALT             6

#define KVM_REQ_MMU_SYNC           7

#define KVM_REQ_MMU_SYNC           7

#define KVM_REQ_KVMCLOCK_UPDATE    8





#define KVM_USERSPACE_IRQ_SOURCE_ID	0

#define KVM_USERSPACE_IRQ_SOURCE_ID	0