Re: [PATCH v8 09/20] KVM: nVMX: Propagate extended instruction information

["Chang S. Bae" <chang.seok.bae@intel.com>]

On 9/30/2026 2:52 PM, sashiko-bot@kernel.org wrote:
> 
>> @@ -4773,6 +4773,12 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
>>   		vmcs12->vm_exit_intr_info = exit_intr_info;
>>   		vmcs12->vm_exit_instruction_len = exit_insn_len;
>>   		vmcs12->vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
>> +		/*
>> +		 * The APX enumeration guarantees the presence of the extended
>> +		 * fields. This CPUID bit alone is sufficient to rely on it.
>> +		 */
>> +		if (guest_cpu_cap_has(vcpu, X86_FEATURE_APX))
>> +			vmcs12->extended_instruction_info = vmcs_read64(EXTENDED_INSTRUCTION_INFO);
> 
> [Severity: High]
> Does this unconditional read cause an issue when KVM is running as an L1
> hypervisor on top of Hyper-V?

When it is not ready, the hypervisor won't expose APX to the guest. So
this is not an unconditional read.

Thanks,
Chang