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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2/3/25 19:45, Sean Christopherson wrote: > Unless there's a very, very good reason to support a use case that generates > ExtInts during boot, but _only_ during boot, and otherwise doesn't have any APICv > ihibits, I'm leaning towards making SVM's IRQ window inhibit sticky, i.e. never > clear it. BIOS tends to use PIT, so that may be too much. With respect to Naveen's report of contention on apicv_update_lock, I would go with the sticky-bit idea but apply it to APICV_INHIBIT_REASON_PIT_REINJ. Plus, to avoid crazy ExtINT configurations, something like this: diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 3ec6197b1386..3e358d55b676 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1295,6 +1295,11 @@ enum kvm_apicv_inhibit { */ APICV_INHIBIT_REASON_LOGICAL_ID_ALIASED, + /* + * AVIC is disabled because more than one vCPU has extint unmasked + */ + APICV_INHIBIT_REASON_EXTINT, + /*********************************************************/ /* INHIBITs that are relevant only to the Intel's APICv. */ /*********************************************************/ diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 71544b0f6301..33a5f4ef42bd 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -377,6 +377,7 @@ void kvm_recalculate_apic_map(struct kvm *kvm) struct kvm_apic_map *new, *old = NULL; struct kvm_vcpu *vcpu; unsigned long i; + int extint_cnt = 0; u32 max_id = 255; /* enough space for any xAPIC ID */ bool xapic_id_mismatch; int r; @@ -432,6 +433,8 @@ void kvm_recalculate_apic_map(struct kvm *kvm) if (!kvm_apic_present(vcpu)) continue; + extint_cnt += kvm_apic_accept_pic_intr(vcpu); + r = kvm_recalculate_phys_map(new, vcpu, &xapic_id_mismatch); if (r) { kvfree(new); @@ -457,6 +460,11 @@ void kvm_recalculate_apic_map(struct kvm *kvm) else kvm_clear_apicv_inhibit(kvm, APICV_INHIBIT_REASON_PHYSICAL_ID_ALIASED); + if (extint_cnt > 1) + kvm_set_apicv_inhibit(kvm, APICV_INHIBIT_REASON_EXTINT); + else + kvm_clear_apicv_inhibit(kvm, APICV_INHIBIT_REASON_EXTINT); + if (!new || new->logical_mode == KVM_APIC_MODE_MAP_DISABLED) kvm_set_apicv_inhibit(kvm, APICV_INHIBIT_REASON_LOGICAL_ID_ALIASED); else diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h index 57ff79bc02a4..ba2fc7dd8ca2 100644 --- a/arch/x86/kvm/svm/svm.h +++ b/arch/x86/kvm/svm/svm.h @@ -676,6 +676,7 @@ extern struct kvm_x86_nested_ops svm_nested_ops; BIT(APICV_INHIBIT_REASON_HYPERV) | \ BIT(APICV_INHIBIT_REASON_NESTED) | \ BIT(APICV_INHIBIT_REASON_IRQWIN) | \ + BIT(APICV_INHIBIT_REASON_EXTINT) | \ BIT(APICV_INHIBIT_REASON_PIT_REINJ) | \ BIT(APICV_INHIBIT_REASON_BLOCKIRQ) | \ BIT(APICV_INHIBIT_REASON_SEV) | \ I don't love adding another inhibit reason but, together, these two should remove the contention on apicv_update_lock. Another idea could be to move IRQWIN to per-vCPU reason but Maxim tells me that it's not so easy. Paolo