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SubjectRe: [PATCH 6/6] KVM: VMX: enable IPI virtualization
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On 7/19/2021 4:32 AM, Paolo Bonzini wrote:
> On 17/07/21 05:55, Zeng Guang wrote:
>>>> +    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.

enable_ipiv associate with "IPI virtualization" setting in tertiary exec
controls and
enable_apicv which depends on cpu_has_vmx_apicv(). kvm_vcpu_apicv_active
still
can be false even if enable_ipiv is true, e.g. in case irqchip not
emulated in kernel.

It's ok to use enable_ipiv here. vmcs setup succeed for IPIv but it
won't take into effect as
false kvm_vcpu_apicv_active disable “IPI virtualization" in this case.

> Paolo
>

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