KVM: x86: ioapic: Fix level-triggered EOI and userspace I/OAPIC reconfigure race

When scanning userspace I/OAPIC entries, intercept EOI for level-triggered
IRQs if the current vCPU has a pending and/or in-service IRQ for the
vector in its local API, even if the vCPU doesn't match the new entry's
destination.  This fixes a race between userspace I/OAPIC reconfiguration
and IRQ delivery that results in the vector's bit being left set in the
remote IRR due to the eventual EOI not being forwarded to the userspace
I/OAPIC.

Commit 0fc5a36dd6b3 ("KVM: x86: ioapic: Fix level-triggered EOI and IOAPIC
reconfigure race") fixed the in-kernel IOAPIC, but not the userspace
IOAPIC configuration, which has a similar race.

Fixes: 0fc5a36dd6b3 ("KVM: x86: ioapic: Fix level-triggered EOI and IOAPIC reconfigure race")
Signed-off-by: Adamos Ttofari <attofari@amazon.de>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20221208094415.12723-1-attofari@amazon.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
index 0687162c4f227d8ee9bfd45c70d2d5f7e3c70535..3742d9adacfc1a7b01b2b0f5431953ba16fb43ca 100644 (file)
--- a/arch/x86/kvm/irq_comm.c
+++ b/arch/x86/kvm/irq_comm.c
@@ -426,8 +426,9 @@ void kvm_scan_ioapic_routes(struct kvm_vcpu *vcpu,
                        kvm_set_msi_irq(vcpu->kvm, entry, &irq);
 
                        if (irq.trig_mode &&
-                           kvm_apic_match_dest(vcpu, NULL, APIC_DEST_NOSHORT,
-                                               irq.dest_id, irq.dest_mode))
+                           (kvm_apic_match_dest(vcpu, NULL, APIC_DEST_NOSHORT,
+                                                irq.dest_id, irq.dest_mode) ||
+                            kvm_apic_pending_eoi(vcpu, irq.vector)))
                                __set_bit(irq.vector, ioapic_handled_vectors);
                }
        }