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authorMarcelo Tosatti <mtosatti@redhat.com>2014-11-04 21:30:44 -0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-03-06 14:40:52 -0800
commitb7e4884e64bcfefd359812a96505ecfa67c3ce8d (patch)
treeee063ddaa97f09329506f06e9c00defc53501e25 /arch
parentef6bb317ad2f9fc585fcb87e6393763ea9850265 (diff)
downloadlinux-linaro-stable-b7e4884e64bcfefd359812a96505ecfa67c3ce8d.tar.gz
KVM: x86: update masterclock values on TSC writes
commit 7f187922ddf6b67f2999a76dcb71663097b75497 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>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/x86.c19
1 files changed, 10 insertions, 9 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index adfc30d9f9f4..41ba726c1ce2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -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,