Re: [PATCH v2 2/3] KVM: SVM: Don't update IRTEs if APICv/AVIC is disable

Jim Mattson
2025-03-20T16:08:44Z

On Thu, Mar 20, 2025 at 7:31 AM Sean Christopherson <seanjc@google.com> wrote:
>
> Skip IRTE updates if AVIC is disabled/unsupported, as forcing the IRTE
> into remapped mode (kvm_vcpu_apicv_active() will never be true) is
> unnecessary and wasteful. The IOMMU driver is responsible for putting
> IRTEs into remapped mode when an IRQ is allocated by a device, long before
> that device is assigned to a VM. I.e. the kernel as a whole has major
> issues if the IRTE isn't already in remapped mode.
>
> Opportunsitically kvm_arch_has_irq_bypass() to query for APICv/AVIC, so
> so that all checks in KVM x86 incorporate the same information.
>
> Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Nit: "disable" -> "disabled" in the shortlog.