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SubjectRe: [PATCH 6/6] KVM: VMX: enable IPI virtualization
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On 7/19/2021 9:58 PM, Paolo Bonzini wrote:
> On 19/07/21 14:38, Zeng Guang wrote:
>>> 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.
> Right, kvm_vcpu_apicv_active *is* set in init_vmcs. But there's an
> "if (kvm_vcpu_apicv_active(&vmx->vcpu))" above. You can just stick
>
> if (enable_ipicv)
> install_pid(vmx);
Ok, got your point now. I will revise to remove vmx->ipiv_active. Thanks.
> inside there. As to the other occurrences of vmx->ipiv_active, look here:
>
>> + if (!kvm_vcpu_apicv_active(vcpu))
>> + return;
>> +
>> + if ((!kvm_arch_has_assigned_device(vcpu->kvm) ||
>> + !irq_remapping_cap(IRQ_POSTING_CAP)) &&
>> + !to_vmx(vcpu)->ipiv_active)
>> return;
>>
> This one can be enable_ipiv because APICv must be active.
>
>> + if (!kvm_vcpu_apicv_active(vcpu))
>> + return 0;
>> +
>> + /* Put vCPU into a list and set NV to wakeup vector if it is
>> + * one of the following cases:
>> + * 1. any assigned device is in use.
>> + * 2. IPI virtualization is enabled.
>> + */
>> + if ((!kvm_arch_has_assigned_device(vcpu->kvm) ||
>> + !irq_remapping_cap(IRQ_POSTING_CAP)) && !to_vmx(vcpu)->ipiv_active)
>> return 0;
> This one can be !enable_ipiv because APICv must be active.
>
>> @@ -3870,6 +3877,8 @@ static void vmx_update_msr_bitmap_x2apic(struct kvm_vcpu *vcpu, u8 mode)
>> vmx_enable_intercept_for_msr(vcpu, X2APIC_MSR(APIC_TMCCT), MSR_TYPE_RW);
>> vmx_disable_intercept_for_msr(vcpu, X2APIC_MSR(APIC_EOI), MSR_TYPE_W);
>> vmx_disable_intercept_for_msr(vcpu, X2APIC_MSR(APIC_SELF_IPI), MSR_TYPE_W);
>> + vmx_set_intercept_for_msr(vcpu, X2APIC_MSR(APIC_ICR),
>> + MSR_TYPE_RW, !to_vmx(vcpu)->ipiv_active);
>> }
>> }
> Is inside "if (mode & MSR_BITMAP_MODE_X2APIC_APICV)" so APICv must be
> activ; so it can be enable_ipiv as well.
>
> In conclusion, you do not need vmx->ipiv_active.
>
> Paolo
>

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