Re: [PATCH 6/6] KVM: VMX: enable IPI virtualization

[Paolo Bonzini <pbonzini@redhat.com>]

On 17/07/21 05:55, Zeng Guang wrote:
>>>      if (_cpu_based_exec_control & 
>>> CPU_BASED_ACTIVATE_TERTIARY_CONTROLS) {
>>> -        u64 opt3 = 0;
>>> +        u64 opt3 = enable_ipiv ? TERTIARY_EXEC_IPI_VIRT : 0;
>>>          u64 min3 = 0;
>>
>> I like the idea of changing opt3, but it's different from how 
>> setup_vmcs_config works for the other execution controls.  Let me 
>> think if it makes sense to clean this up, and move the handling of 
>> other module parameters from hardware_setup() to setup_vmcs_config().
>>
> May be an exception for ipiv feature ?

Yes, possibly.  I'll look into using this idea for other parameters.

>>> +    if (vmx->ipiv_active)
>>> +        install_pid(vmx);
>>
>> This should be if (enable_ipiv) instead, I think.
>>
>> In fact, in all other places that are using vmx->ipiv_active, you can 
>> actually replace it with enable_ipiv; they are all reached only with 
>> kvm_vcpu_apicv_active(vcpu) == true.
>>
> enable_ipiv as a global variable indicates the hardware capability to 
> enable IPIv. Each VM may have different IPIv configuration according to 
> kvm_vcpu_apicv_active status. So we use ipiv_active per VM to enclose 
> IPIv related operations.

Understood, but in practice all uses of vmx->ipiv_active are guarded by 
kvm_vcpu_apicv_active so they are always reached with vmx->ipiv_active 
== enable_ipiv.

The one above instead seems wrong and should just use enable_ipiv.

Paolo