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| author |   Paolo Bonzini <pbonzini@redhat.com> | 2016-11-16 18:31:30 +0100 |
|---|---|---|
| committer |   Radim Krčmář <rkrcmar@redhat.com> | 2016-11-19 18:03:03 +0100 |
| commit | 8b9534406456313beb7bf9051150b50c63049ab7 (patch) | |
| tree | 029c08e8e130130e8e59331f8b15560a7e119c66 /arch/x86/kvm/x86.c | |
| parent | Merge tag 'kvm-arm-for-4.9-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm (diff) | |
| download | linux-dev-8b9534406456313beb7bf9051150b50c63049ab7.tar.xz linux-dev-8b9534406456313beb7bf9051150b50c63049ab7.zip | |
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>
Diffstat (limited to '')
| -rw-r--r-- | arch/x86/kvm/x86.c | 21 |
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) |