Messages in this thread | | | From | Like Xu <> | Subject | Re: [PATCH 3/5] KVM: VMX: RTIT_CTL_BRANCH_EN has no dependency on other CPUID bit | Date | Wed, 25 Aug 2021 11:30:49 +0800 |
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+Alexander
On 24/8/2021 7:07 pm, Xiaoyao Li wrote: > Per Intel SDM, RTIT_CTL_BRANCH_EN bit has no dependency on any CPUID > leaf 0x14. > > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com> > --- > arch/x86/kvm/vmx/vmx.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 7ed96c460661..4a70a6d2f442 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -7116,7 +7116,8 @@ static void update_intel_pt_cfg(struct kvm_vcpu *vcpu) > > /* Initialize and clear the no dependency bits */ > vmx->pt_desc.ctl_bitmask = ~(RTIT_CTL_TRACEEN | RTIT_CTL_OS | > - RTIT_CTL_USR | RTIT_CTL_TSC_EN | RTIT_CTL_DISRETC); > + RTIT_CTL_USR | RTIT_CTL_TSC_EN | RTIT_CTL_DISRETC | > + RTIT_CTL_BRANCH_EN); > > /* > * If CPUID.(EAX=14H,ECX=0):EBX[0]=1 CR3Filter can be set otherwise > @@ -7134,12 +7135,11 @@ static void update_intel_pt_cfg(struct kvm_vcpu *vcpu) > RTIT_CTL_CYC_THRESH | RTIT_CTL_PSB_FREQ); > > /* > - * If CPUID.(EAX=14H,ECX=0):EBX[3]=1 MTCEn BranchEn and > - * MTCFreq can be set > + * If CPUID.(EAX=14H,ECX=0):EBX[3]=1 MTCEn and MTCFreq can be set
If CPUID.(EAX=14H,ECX=0):EBX[3]=1,
"indicates support of MTC timing packet and suppression of COFI-based packets."
Per 31.2.5.4 Branch Enable (BranchEn),
"If BranchEn is not set, then relevant COFI packets (TNT, TIP*, FUP, MODE.*) are suppressed."
I think if the COFI capability is suppressed, the software can't set the BranchEn bit, right ?
> */ > if (intel_pt_validate_cap(vmx->pt_desc.caps, PT_CAP_mtc)) > vmx->pt_desc.ctl_bitmask &= ~(RTIT_CTL_MTC_EN | > - RTIT_CTL_BRANCH_EN | RTIT_CTL_MTC_RANGE); > + RTIT_CTL_MTC_RANGE); > > /* If CPUID.(EAX=14H,ECX=0):EBX[4]=1 FUPonPTW and PTWEn can be set */ > if (intel_pt_validate_cap(vmx->pt_desc.caps, PT_CAP_ptwrite)) >
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