kvm: ioapic: Lazy update IOAPIC EOI

In-kernel IOAPIC does not receive EOI with AMD SVM AVIC
since the processor accelerate write to APIC EOI register and
does not trap if the interrupt is edge-triggered.

Workaround this by lazy check for pending APIC EOI at the time when
setting new IOPIC irq, and update IOAPIC EOI if no pending APIC EOI.
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/ioapic.c

@@ -49,6 +49,11 @@
 static int ioapic_service(struct kvm_ioapic *vioapic, int irq,
 		bool line_status);
 
+static void kvm_ioapic_update_eoi_one(struct kvm_vcpu *vcpu,
+				      struct kvm_ioapic *ioapic,
+				      int trigger_mode,
+				      int pin);
+
 static unsigned long ioapic_read_indirect(struct kvm_ioapic *ioapic,
 					  unsigned long addr,
 					  unsigned long length)
@@ -177,6 +182,31 @@ static bool rtc_irq_check_coalesced(struct kvm_ioapic *ioapic)
 	return false;
 }
 
+static void ioapic_lazy_update_eoi(struct kvm_ioapic *ioapic, int irq)
+{
+	int i;
+	struct kvm_vcpu *vcpu;
+	union kvm_ioapic_redirect_entry *entry = &ioapic->redirtbl[irq];
+
+	kvm_for_each_vcpu(i, vcpu, ioapic->kvm) {
+		if (!kvm_apic_match_dest(vcpu, NULL, APIC_DEST_NOSHORT,
+					 entry->fields.dest_id,
+					 entry->fields.dest_mode) ||
+		    kvm_apic_pending_eoi(vcpu, entry->fields.vector))
+			continue;
+
+		/*
+		 * If no longer has pending EOI in LAPICs, update
+		 * EOI for this vetor.
+		 */
+		rtc_irq_eoi(ioapic, vcpu, entry->fields.vector);
+		kvm_ioapic_update_eoi_one(vcpu, ioapic,
+					  entry->fields.trig_mode,
+					  irq);
+		break;
+	}
+}
+
 static int ioapic_set_irq(struct kvm_ioapic *ioapic, unsigned int irq,
 		int irq_level, bool line_status)
 {
@@ -194,6 +224,15 @@ static int ioapic_set_irq(struct kvm_ioapic *ioapic, unsigned int irq,
 		goto out;
 	}
 
+	/*
+	 * AMD SVM AVIC accelerate EOI write and do not trap,
+	 * in-kernel IOAPIC will not be able to receive the EOI.
+	 * In this case, we do lazy update of the pending EOI when
+	 * trying to set IOAPIC irq.
+	 */
+	if (kvm_apicv_activated(ioapic->kvm))
+		ioapic_lazy_update_eoi(ioapic, irq);
+
 	/*
 	 * Return 0 for coalesced interrupts; for edge-triggered interrupts,
 	 * this only happens if a previous edge has not been delivered due