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authorPaolo Bonzini <pbonzini@redhat.com>2016-11-16 18:31:30 +0100
committerRadim Krčmář <rkrcmar@redhat.com>2016-11-19 18:03:03 +0100
commit8b9534406456313beb7bf9051150b50c63049ab7 (patch)
tree029c08e8e130130e8e59331f8b15560a7e119c66
parente5dbc4bf0b8c9ab50cc5699214240e84515be6eb (diff)
KVM: x86: do not go through vcpu in __get_kvmclock_ns
Going through the first VCPU is wrong if you follow a KVM_SET_CLOCK with a KVM_GET_CLOCK immediately after, without letting the VCPU run and call kvm_guest_time_update. To fix this, compute the kvmclock value ourselves, using the master clock (tsc, nsec) pair as the base and the host CPU frequency as the scale. Reported-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
-rw-r--r--arch/x86/kvm/x86.c21
1 files changed, 13 insertions, 8 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3017de0431bd..7d3d9d4d6124 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1724,18 +1724,23 @@ static void kvm_gen_update_masterclock(struct kvm *kvm)
static u64 __get_kvmclock_ns(struct kvm *kvm)
{
- struct kvm_vcpu *vcpu = kvm_get_vcpu(kvm, 0);
struct kvm_arch *ka = &kvm->arch;
- s64 ns;
+ struct pvclock_vcpu_time_info hv_clock;
- if (vcpu->arch.hv_clock.flags & PVCLOCK_TSC_STABLE_BIT) {
- u64 tsc = kvm_read_l1_tsc(vcpu, rdtsc());
- ns = __pvclock_read_cycles(&vcpu->arch.hv_clock, tsc);
- } else {
- ns = ktime_get_boot_ns() + ka->kvmclock_offset;
+ spin_lock(&ka->pvclock_gtod_sync_lock);
+ if (!ka->use_master_clock) {
+ spin_unlock(&ka->pvclock_gtod_sync_lock);
+ return ktime_get_boot_ns() + ka->kvmclock_offset;
}
- return ns;
+ hv_clock.tsc_timestamp = ka->master_cycle_now;
+ hv_clock.system_time = ka->master_kernel_ns + ka->kvmclock_offset;
+ spin_unlock(&ka->pvclock_gtod_sync_lock);
+
+ kvm_get_time_scale(NSEC_PER_SEC, __this_cpu_read(cpu_tsc_khz) * 1000LL,
+ &hv_clock.tsc_shift,
+ &hv_clock.tsc_to_system_mul);
+ return __pvclock_read_cycles(&hv_clock, rdtsc());
}
u64 get_kvmclock_ns(struct kvm *kvm)