Re: [PATCH v4 12/17] svm: Temporary deactivate AVIC during ExtINT handling

[Paolo Bonzini]

On 01/11/19 23:41, Suthikulpanit, Suravee wrote:
> +		/*
> +		 * IRQ window is not needed when AVIC is enabled,
> +		 * unless we have pending ExtINT since it cannot be injected
> +		 * via AVIC. In such case, we need to temporarily disable AVIC,
> +		 * and fallback to injecting IRQ via V_IRQ.
> +		 */
> +		if (kvm_vcpu_apicv_active(vcpu))
> +			svm_request_update_avic(vcpu, false);

This must be pretty heavy-weight on SMP VMs, even if most ExtINT guests
do not need SMP in the guest.  One alternative is to enable/disable
APICv when LVT or IOAPIC registers are written with ExtINT mode.  Not a
blocker, just an idea to consider.

Paolo