Messages in this thread | | | Date | Tue, 12 Jul 2022 11:23:33 +0800 | Subject | Re: [PATCH] KVM: VMX: Update PT MSR intercepts during filter change iff PT in host+guest | From | Xiaoyao Li <> |
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On 7/12/2022 9:58 AM, Sean Christopherson wrote: > Update the Processor Trace (PT) MSR intercepts during a filter change if > and only if PT may be exposed to the guest, i.e. only if KVM is operating > in the so called "host+guest" mode where PT can be used simultaneously by > both the host and guest. If PT is in system mode, the host is the sole > owner of PT and the MSRs should never be passed through to the guest. > > Luckily the missed check only results in unnecessary work, as select RTIT > MSRs are passed through only when RTIT tracing is enabled "in" the guest, > and tracing can't be enabled in the guest when KVM is in system mode > (writes to guest.MSR_IA32_RTIT_CTL are disallowed).
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
> Cc: Xiaoyao Li <xiaoyao.li@intel.com> > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- > arch/x86/kvm/vmx/vmx.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 74ca64e97643..e6ab2c2c4d3b 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -4004,7 +4004,9 @@ static void vmx_msr_filter_changed(struct kvm_vcpu *vcpu) > vmx_disable_intercept_for_msr(vcpu, msr, MSR_TYPE_W); > } > > - pt_update_intercept_for_msr(vcpu); > + /* PT MSRs can be passed through iff PT is exposed to the guest. */ > + if (vmx_pt_mode_is_host_guest()) > + pt_update_intercept_for_msr(vcpu); > } > > static inline void kvm_vcpu_trigger_posted_interrupt(struct kvm_vcpu *vcpu, > > base-commit: 5406e590ac8fa33e390616031370806cdbcc5791
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