Re: [PATCH v2 07/25] KVM: VMX: Set intercept for FRED MSRs

On Wed, Feb 07, 2024, Xin Li wrote:

@@ -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);

"enumerated" isn't correct. Userspace can enumerate FRED to the guest even if FRED is unsupported in KVM.

Planning for a future where this becomes guest_cpu_cap_has(), maybe "has_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);

} static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) -- 2.43.0