KVM: x86: Unify TSC logic

Move the TSC control logic from the vendor backends into x86.c
by adding adjust_tsc_offset to x86 ops.  Now all TSC decisions
can be done in one place.

Signed-off-by: Zachary Amsden <zamsden@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 14 insertions, 3 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a8dee58e8716..468fafaed1ae 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -973,9 +973,9 @@ static int kvm_write_guest_time(struct kvm_vcpu *v)
                 return 1;
         }
 
-        if (unlikely(vcpu->hv_clock_tsc_khz != this_tsc_khz)) {
+        if (unlikely(vcpu->hw_tsc_khz != this_tsc_khz)) {
                 kvm_set_time_scale(this_tsc_khz, &vcpu->hv_clock);
-                vcpu->hv_clock_tsc_khz = this_tsc_khz;
+                vcpu->hw_tsc_khz = this_tsc_khz;
         }
 
         /* With all the info we got, fill in the values */
@@ -1866,13 +1866,24 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
         }
 
         kvm_x86_ops->vcpu_load(vcpu, cpu);
-        kvm_request_guest_time_update(vcpu);
+        if (unlikely(vcpu->cpu != cpu)) {
+                /* Make sure TSC doesn't go backwards */
+                s64 tsc_delta = !vcpu->arch.last_host_tsc ? 0 :
+                                native_read_tsc() - vcpu->arch.last_host_tsc;
+                if (tsc_delta < 0)
+                        mark_tsc_unstable("KVM discovered backwards TSC");
+                if (check_tsc_unstable())
+                        kvm_x86_ops->adjust_tsc_offset(vcpu, -tsc_delta);
+                kvm_migrate_timers(vcpu);
+                vcpu->cpu = cpu;
+        }
 }
 
 void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 {
         kvm_x86_ops->vcpu_put(vcpu);
         kvm_put_guest_fpu(vcpu);
+        vcpu->arch.last_host_tsc = native_read_tsc();
 }
 
 static int is_efer_nx(void)