KVM: x86: Move TSC reset out of vmcb_init

commit 47008cd887c1836bcadda123ba73e1863de7a6c4 upstream.

The VMCB is reset whenever we receive a startup IPI, so Linux is setting
TSC back to zero happens very late in the boot process and destabilizing
the TSC.  Instead, just set TSC to zero once at VCPU creation time.

Why the separate patch?  So git-bisect is your friend.

Signed-off-by: Zachary Amsden <zamsden@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index b15fab64ebd779f6ba6dd6f2845eb675993f1c77..6a2321136f28d6edf1ed1e4af19d857ca1e50288 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -621,7 +621,6 @@ static void init_vmcb(struct vcpu_svm *svm)
 
        control->iopm_base_pa = iopm_base;
        control->msrpm_base_pa = __pa(svm->msrpm);
-       control->tsc_offset = 0-native_read_tsc();
        control->int_ctl = V_INTR_MASKING_MASK;
 
        init_seg(&save->es);
@@ -754,6 +753,7 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
        svm->vmcb_pa = page_to_pfn(page) << PAGE_SHIFT;
        svm->asid_generation = 0;
        init_vmcb(svm);
+       svm->vmcb->control.tsc_offset = 0-native_read_tsc();
 
        fx_init(&svm->vcpu);
        svm->vcpu.fpu_active = 1;