From 057aa61bc992f2d27218b6558b0115d5623f1a7b Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 8 Oct 2021 19:12:13 -0700 Subject: [PATCH] KVM: VMX: Skip Posted Interrupt updates if APICv is hard disabled Explicitly skip posted interrupt updates if APICv is disabled in all of KVM, or if the guest doesn't have an in-kernel APIC. The PI descriptor is kept up-to-date if APICv is inhibited, e.g. so that re-enabling APICv doesn't require a bunch of updates, but neither the module param nor the APIC type can be changed on-the-fly. Signed-off-by: Sean Christopherson Message-Id: <20211009021236.4122790-21-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/posted_intr.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c index 41f946e2123e..ee4ddc6e268b 100644 --- a/arch/x86/kvm/vmx/posted_intr.c +++ b/arch/x86/kvm/vmx/posted_intr.c @@ -29,11 +29,14 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu) unsigned int dest; /* - * In case of hot-plug or hot-unplug, we may have to undo - * vmx_vcpu_pi_put even if there is no assigned device. And we - * always keep PI.NDST up to date for simplicity: it makes the - * code easier, and CPU migration is not a fast path. + * To simplify hot-plug and dynamic toggling of APICv, keep PI.NDST and + * PI.SN up-to-date even if there is no assigned device or if APICv is + * deactivated due to a dynamic inhibit bit, e.g. for Hyper-V's SyncIC. */ + if (!enable_apicv || !lapic_in_kernel(vcpu)) + return; + + /* Nothing to do if PI.SN and PI.NDST both have the desired value. */ if (!pi_test_sn(pi_desc) && vcpu->cpu == cpu) return; -- 2.25.1