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KVM: x86: update masterclock values on TSC writes

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commit 7f187922dd upstream.

When the guest writes to the TSC, the masterclock TSC copy must be
updated as well along with the TSC_OFFSET update, otherwise a negative
tsc_timestamp is calculated at kvm_guest_time_update.

Once "if (!vcpus_matched && ka->use_master_clock)" is simplified to
"if (ka->use_master_clock)", the corresponding "if (!ka->use_master_clock)"
becomes redundant, so remove the do_request boolean and collapse
everything into a single condition.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Marcelo Tosatti 2014-11-04 21:30:44 -02:00 committed by Greg Kroah-Hartman
parent ef6bb317ad
commit b7e4884e64
1 changed files with 10 additions and 9 deletions
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19
arch/x86/kvm/x86.c
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@ -1182,21 +1182,22 @@ void kvm_track_tsc_matching(struct kvm_vcpu *vcpu)
{
#ifdef CONFIG_X86_64
bool vcpus_matched;
bool do_request = false;
struct kvm_arch *ka = &vcpu->kvm->arch;
struct pvclock_gtod_data *gtod = &pvclock_gtod_data;
vcpus_matched = (ka->nr_vcpus_matched_tsc + 1 ==
atomic_read(&vcpu->kvm->online_vcpus));
if (vcpus_matched && gtod->clock.vclock_mode == VCLOCK_TSC)
if (!ka->use_master_clock)
do_request = 1;
if (!vcpus_matched && ka->use_master_clock)
do_request = 1;
if (do_request)
/*
* Once the masterclock is enabled, always perform request in
* order to update it.
*
* In order to enable masterclock, the host clocksource must be TSC
* and the vcpus need to have matched TSCs. When that happens,
* perform request to enable masterclock.
*/
if (ka->use_master_clock ||
(gtod->clock.vclock_mode == VCLOCK_TSC && vcpus_matched))
kvm_make_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu);
trace_kvm_track_tsc(vcpu->vcpu_id, ka->nr_vcpus_matched_tsc,