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>

arch/x86/kvm/svm.c

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index ea41c55..ff28f65 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -715,6 +715,15 @@
 	svm->vmcb->control.tsc_offset = offset + g_tsc_offset;
 }
 
+static void svm_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment)
+{
+	struct vcpu_svm *svm = to_svm(vcpu);
+
+	svm->vmcb->control.tsc_offset += adjustment;
+	if (is_nested(svm))
+		svm->nested.hsave->control.tsc_offset += adjustment;
+}
+
 static void init_vmcb(struct vcpu_svm *svm)
 {
 	struct vmcb_control_area *control = &svm->vmcb->control;
@@ -961,20 +970,6 @@
 	int i;
 
 	if (unlikely(cpu != vcpu->cpu)) {
-		u64 delta;
-
-		if (check_tsc_unstable()) {
-			/*
-			 * Make sure that the guest sees a monotonically
-			 * increasing TSC.
-			 */
-			delta = vcpu->arch.host_tsc - native_read_tsc();
-			svm->vmcb->control.tsc_offset += delta;
-			if (is_nested(svm))
-				svm->nested.hsave->control.tsc_offset += delta;
-		}
-		vcpu->cpu = cpu;
-		kvm_migrate_timers(vcpu);
 		svm->asid_generation = 0;
 	}
 
@@ -990,8 +985,6 @@
 	++vcpu->stat.host_state_reload;
 	for (i = 0; i < NR_HOST_SAVE_USER_MSRS; i++)
 		wrmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
-
-	vcpu->arch.host_tsc = native_read_tsc();
 }
 
 static unsigned long svm_get_rflags(struct kvm_vcpu *vcpu)
@@ -3553,6 +3546,7 @@
 	.has_wbinvd_exit = svm_has_wbinvd_exit,
 
 	.write_tsc_offset = svm_write_tsc_offset,
+	.adjust_tsc_offset = svm_adjust_tsc_offset,
 };
 
 static int __init svm_init(void)