If nested tsc scaling is disabled, MSR_AMD64_TSC_RATIO should never have non default value.
Due to way nested tsc scaling support was implmented in qemu, it would set this msr to 0 when nested tsc scaling was disabled. Ignore that value for now, as it causes no harm.
Fixes: 5228eb96a487 ("KVM: x86: nSVM: implement nested TSC scaling") Cc: stable@vger.kernel.org
Signed-off-by: Maxim Levitsky mlevitsk@redhat.com --- arch/x86/kvm/svm/svm.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 7038c76fa841..b80ad471776f 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -2705,8 +2705,23 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) u64 data = msr->data; switch (ecx) { case MSR_AMD64_TSC_RATIO: - if (!msr->host_initiated && !svm->tsc_scaling_enabled) - return 1; + + if (!svm->tsc_scaling_enabled) { + + if (!msr->host_initiated) + return 1; + /* + * In case TSC scaling is not enabled, always + * leave this MSR at the default value. + * + * Due to bug in qemu 6.2.0, it would try to set + * this msr to 0 if tsc scaling is not enabled. + * Ignore this value as well. + */ + if (data != 0 && data != svm->tsc_ratio_msr) + return 1; + break; + }
if (data & TSC_RATIO_RSVD) return 1;