Messages in this thread | | | Date | Thu, 24 Feb 2022 15:22:41 +0100 | Subject | Re: [PATCH] KVM: x86: nSVM: disallow userspace setting of MSR_AMD64_TSC_RATIO to non default value when tsc scaling disabled | From | Paolo Bonzini <> |
| |
On 2/23/22 12:56, Maxim Levitsky wrote: > 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(-)
Queued, thanks.
Paolo
> 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;
| |