KVM: SVM: Handle tsc in svm_get_msr/svm_set_msr correctly

When running nested we need to touch the l1 guests
tsc_offset. Otherwise changes will be lost or a wrong value
be read.

Cc: stable@kernel.org
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index bf5799d..c17404a 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2059,10 +2059,14 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 *data)
 
        switch (ecx) {
        case MSR_IA32_TSC: {
-               u64 tsc;
+               u64 tsc_offset;
 
-               rdtscll(tsc);
-               *data = svm->vmcb->control.tsc_offset + tsc;
+               if (is_nested(svm))
+                       tsc_offset = svm->nested.hsave->control.tsc_offset;
+               else
+                       tsc_offset = svm->vmcb->control.tsc_offset;
+
+               *data = tsc_offset + native_read_tsc();
                break;
        }
        case MSR_K6_STAR:
@@ -2148,10 +2152,17 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 data)
 
        switch (ecx) {
        case MSR_IA32_TSC: {
-               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->nested.hsave->control.tsc_offset;
+                       svm->nested.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: