Re: [PATCH 2/7] KVM: SVM: Disable interception of FRED MSRs for FRED supported guests

[Shivansh Dhiman]

On 07-03-2026 07:40, Sean Christopherson wrote:
> On Thu, Jan 29, 2026, Shivansh Dhiman wrote:
>> +static void svm_recalc_fred_msr_intercepts(struct kvm_vcpu *vcpu)
>> +{
>> +	struct vcpu_svm *svm = to_svm(vcpu);
>> +	bool fred_enabled = svm->vmcb->control.virt_ext & FRED_VIRT_ENABLE_MASK;
> 
> Please use guest_cpu_cap_has().  The VMCB enable bit is a reflection of the
> guest's capabilities, not the other way around.

That makes sense. Will do.

> 
> And s/fred_enabled/intercept.

Ack.

- Shivansh

> 
>> +
>> +	svm_set_intercept_for_msr(vcpu, MSR_IA32_FRED_RSP0, MSR_TYPE_RW, !fred_enabled);
>> +	svm_set_intercept_for_msr(vcpu, MSR_IA32_FRED_RSP1, MSR_TYPE_RW, !fred_enabled);
>> +	svm_set_intercept_for_msr(vcpu, MSR_IA32_FRED_RSP2, MSR_TYPE_RW, !fred_enabled);
>> +	svm_set_intercept_for_msr(vcpu, MSR_IA32_FRED_RSP3, MSR_TYPE_RW, !fred_enabled);
>> +	svm_set_intercept_for_msr(vcpu, MSR_IA32_FRED_STKLVLS, MSR_TYPE_RW, !fred_enabled);
>> +	svm_set_intercept_for_msr(vcpu, MSR_IA32_FRED_SSP1, MSR_TYPE_RW, !fred_enabled);
>> +	svm_set_intercept_for_msr(vcpu, MSR_IA32_FRED_SSP2, MSR_TYPE_RW, !fred_enabled);
>> +	svm_set_intercept_for_msr(vcpu, MSR_IA32_FRED_SSP3, MSR_TYPE_RW, !fred_enabled);
>> +	svm_set_intercept_for_msr(vcpu, MSR_IA32_FRED_CONFIG, MSR_TYPE_RW, !fred_enabled);
>> +}
>> +
>>  static void svm_recalc_msr_intercepts(struct kvm_vcpu *vcpu)
>>  {
>>  	struct vcpu_svm *svm = to_svm(vcpu);
>> @@ -795,6 +811,8 @@ static void svm_recalc_msr_intercepts(struct kvm_vcpu *vcpu)
>>  	if (sev_es_guest(vcpu->kvm))
>>  		sev_es_recalc_msr_intercepts(vcpu);
>>  
>> +	svm_recalc_fred_msr_intercepts(vcpu);
>> +
>>  	/*
>>  	 * x2APIC intercepts are modified on-demand and cannot be filtered by
>>  	 * userspace.
>> -- 
>> 2.43.0
>>