[Devel] [PATCH RHEL7 COMMIT] ms/KVM: x86: Use the correct vcpu's TSC rate to compute time scale

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-327.36.1.vz7.19.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.36.1.vz7.19.9
------>
commit 939914a76b621345a6ac65ee6c8de8a3bae03078
Author: Haozhong Zhang <haozhong.zhang at intel.com>
Date:   Wed Nov 16 16:45:59 2016 +0400

    ms/KVM: x86: Use the correct vcpu's TSC rate to compute time scale
    
    This patch makes KVM use virtual_tsc_khz rather than the host TSC rate
    as vcpu's TSC rate to compute the time scale if TSC scaling is enabled.
    
    Signed-off-by: Haozhong Zhang <haozhong.zhang at intel.com>
    Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
    (cherry-picked from commit 27cca94e032c1749825fdd9b6b379e4235cd52e1)
    Signed-off-by: Denis Plotnikov <dplotnikov at virtuozzo.com>
    Signed-off-by: Roman Kagan <rkagan at virtuozzo.com>
---
 arch/x86/kvm/x86.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3913a62..7fcb155 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1780,7 +1780,7 @@ static void kvm_setup_pvclock_page(struct kvm_vcpu *v)
 
 static int kvm_guest_time_update(struct kvm_vcpu *v)
 {
-	unsigned long flags, this_tsc_khz;
+	unsigned long flags, this_tsc_khz, tgt_tsc_khz;
 	struct kvm_vcpu_arch *vcpu = &v->arch;
 	struct kvm_arch *ka = &v->kvm->arch;
 	s64 kernel_ns;
@@ -1841,7 +1841,9 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
 	/* With all the info we got, fill in the values */
 
 	if (unlikely(vcpu->hw_tsc_khz != this_tsc_khz)) {
-		kvm_get_time_scale(NSEC_PER_SEC / 1000, this_tsc_khz,
+		tgt_tsc_khz = kvm_has_tsc_control ?
+			vcpu->virtual_tsc_khz : this_tsc_khz;
+		kvm_get_time_scale(NSEC_PER_SEC / 1000, tgt_tsc_khz,
 				   &vcpu->hv_clock.tsc_shift,
 				   &vcpu->hv_clock.tsc_to_system_mul);
 		vcpu->hw_tsc_khz = this_tsc_khz;