| Message ID | 20250320142022.766201-3-seanjc@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | KVM: x86: Add a module param for device posted IRQs | expand |
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.
diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c index 65fd245a9953..901d8d2dc169 100644 --- a/arch/x86/kvm/svm/avic.c +++ b/arch/x86/kvm/svm/avic.c @@ -898,8 +898,7 @@ int avic_pi_update_irte(struct kvm *kvm, unsigned int host_irq, struct kvm_irq_routing_table *irq_rt; int idx, ret = 0; - if (!kvm_arch_has_assigned_device(kvm) || - !irq_remapping_cap(IRQ_POSTING_CAP)) + if (!kvm_arch_has_assigned_device(kvm) || !kvm_arch_has_irq_bypass()) return 0; pr_debug("SVM: %s: host_irq=%#x, guest_irq=%#x, set=%#x\n",
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> --- arch/x86/kvm/svm/avic.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)