KVM: SVM: Handle tsc in svm_get_msr/svm_set_msr correctly

commit 20824f30 upstream.

When running nested we need to touch the l1 guests
tsc_offset. Otherwise changes will be lost or a wrong value
be read.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

arch/x86/kvm/svm.c

@@ -1956,10 +1956,14 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 *data)
 
 	switch (ecx) {
 	case MSR_IA32_TIME_STAMP_COUNTER: {
-		u64 tsc;
+		u64 tsc_offset;
 
-		rdtscll(tsc);
-		*data = svm->vmcb->control.tsc_offset + tsc;
+		if (is_nested(svm))
+			tsc_offset = svm->hsave->control.tsc_offset;
+		else
+			tsc_offset = svm->vmcb->control.tsc_offset;
+
+		*data = tsc_offset + native_read_tsc();
 		break;
 	}
 	case MSR_K6_STAR:
@@ -2046,10 +2050,17 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 data)
 
 	switch (ecx) {
 	case MSR_IA32_TIME_STAMP_COUNTER: {
-		u64 tsc;
+		u64 tsc_offset = data - native_read_tsc();
+		u64 g_tsc_offset = 0;
+
+		if (is_nested(svm)) {
+			g_tsc_offset = svm->vmcb->control.tsc_offset -
+				       svm->hsave->control.tsc_offset;
+			svm->hsave->control.tsc_offset = tsc_offset;
+		}
+
+		svm->vmcb->control.tsc_offset = tsc_offset + g_tsc_offset;
 
-		rdtscll(tsc);
-		svm->vmcb->control.tsc_offset = data - tsc;
 		break;
 	}
 	case MSR_K6_STAR: