linux-kernel - RE: [PATCH v2 07/25] KVM: VMX: Set intercept for FRED MSRs

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Date: Fri, 19 Apr 2024 17:06:49 +0000
From: "Li, Xin3" <xin3.li@...el.com>
To: "Gao, Chao" <chao.gao@...el.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "linux-doc@...r.kernel.org"
	<linux-doc@...r.kernel.org>, "linux-kselftest@...r.kernel.org"
	<linux-kselftest@...r.kernel.org>, "seanjc@...gle.com" <seanjc@...gle.com>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "corbet@....net"
	<corbet@....net>, "tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>, "bp@...en8.de" <bp@...en8.de>,
	"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>, "x86@...nel.org"
	<x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>, "shuah@...nel.org"
	<shuah@...nel.org>, "vkuznets@...hat.com" <vkuznets@...hat.com>,
	"peterz@...radead.org" <peterz@...radead.org>, "Shankar, Ravi V"
	<ravi.v.shankar@...el.com>, "xin@...or.com" <xin@...or.com>
Subject: RE: [PATCH v2 07/25] KVM: VMX: Set intercept for FRED MSRs

> >+	case MSR_IA32_FRED_RSP0 ... MSR_IA32_FRED_CONFIG:
> >+		/* FRED MSRs should be passthrough to FRED guests only */
> 
> This comment sounds weird. It sounds like the code will be something like:
> 		if guest supports FRED
> 			return true
> 		else
> 			return false
> 
> how about "FRED MSRs are pass-thru'd to guests which enumerate FRED"?
> 
> Or to align with above comment for LBR MSRs, just say
> 
> /* FRED MSRs. These are handled in vmx_vcpu_config_fred_after_set_cpuid() */
> 

Maybe both to not confuse people at all 😊

> >+		return true;
> > 	}
> >
> > 	r = possible_passthrough_msr_slot(msr) != -ENOENT; @@ -7774,10
> >+7777,12 @@ static void update_intel_pt_cfg(struct kvm_vcpu *vcpu)
> >static void vmx_vcpu_config_fred_after_set_cpuid(struct kvm_vcpu *vcpu)
> >{
> > 	struct vcpu_vmx *vmx = to_vmx(vcpu);
> >+	bool fred_enumerated;
> >
> > 	kvm_governed_feature_check_and_set(vcpu, X86_FEATURE_FRED);
> >+	fred_enumerated = guest_can_use(vcpu, X86_FEATURE_FRED);
> >
> >-	if (guest_can_use(vcpu, X86_FEATURE_FRED)) {
> >+	if (fred_enumerated) {
> > 		vm_entry_controls_setbit(vmx, VM_ENTRY_LOAD_IA32_FRED);
> > 		secondary_vm_exit_controls_setbit(vmx,
> >
> SECONDARY_VM_EXIT_SAVE_IA32_FRED | @@ -7788,6 +7793,16 @@
> >static void vmx_vcpu_config_fred_after_set_cpuid(struct kvm_vcpu *vcpu)
> >
> SECONDARY_VM_EXIT_SAVE_IA32_FRED |
> >
> SECONDARY_VM_EXIT_LOAD_IA32_FRED);
> > 	}
> >+
> >+	vmx_set_intercept_for_msr(vcpu, MSR_IA32_FRED_RSP0,
> MSR_TYPE_RW, !fred_enumerated);
> >+	vmx_set_intercept_for_msr(vcpu, MSR_IA32_FRED_RSP1,
> MSR_TYPE_RW, !fred_enumerated);
> >+	vmx_set_intercept_for_msr(vcpu, MSR_IA32_FRED_RSP2,
> MSR_TYPE_RW, !fred_enumerated);
> >+	vmx_set_intercept_for_msr(vcpu, MSR_IA32_FRED_RSP3,
> MSR_TYPE_RW, !fred_enumerated);
> >+	vmx_set_intercept_for_msr(vcpu, MSR_IA32_FRED_STKLVLS,
> MSR_TYPE_RW, !fred_enumerated);
> >+	vmx_set_intercept_for_msr(vcpu, MSR_IA32_FRED_SSP1,
> MSR_TYPE_RW, !fred_enumerated);
> >+	vmx_set_intercept_for_msr(vcpu, MSR_IA32_FRED_SSP2,
> MSR_TYPE_RW, !fred_enumerated);
> >+	vmx_set_intercept_for_msr(vcpu, MSR_IA32_FRED_SSP3,
> MSR_TYPE_RW, !fred_enumerated);
> >+	vmx_set_intercept_for_msr(vcpu, MSR_IA32_FRED_CONFIG, MSR_TYPE_RW,
> >+!fred_enumerated);
> 
> Use a for-loop here? e.g.,
> 	for (i = MSR_IA32_FRED_RSP0; i <= MSR_IA32_FRED_CONFIG; i++)
> > }

Yeah, let me try.