Commit 8b953440 authored by Paolo Bonzini's avatar Paolo Bonzini Committed by Radim Krčmář

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: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
parent e5dbc4bf
...@@ -1724,18 +1724,23 @@ static void kvm_gen_update_masterclock(struct kvm *kvm) ...@@ -1724,18 +1724,23 @@ static void kvm_gen_update_masterclock(struct kvm *kvm)
static u64 __get_kvmclock_ns(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; 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) { spin_lock(&ka->pvclock_gtod_sync_lock);
u64 tsc = kvm_read_l1_tsc(vcpu, rdtsc()); if (!ka->use_master_clock) {
ns = __pvclock_read_cycles(&vcpu->arch.hv_clock, tsc); spin_unlock(&ka->pvclock_gtod_sync_lock);
} else { return ktime_get_boot_ns() + ka->kvmclock_offset;
ns = 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) u64 get_kvmclock_ns(struct kvm *kvm)
......
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