kvm: x86: Deliver MSI IRQ to only lowest prio cpu if msi_redir_hint is true

An MSI interrupt should only be delivered to the lowest priority CPU
when it has RH=1, regardless of the delivery mode. Modified
kvm_is_dm_lowest_prio() to check for either irq->delivery_mode == APIC_DM_LOWPRI
or irq->msi_redir_hint.

Moved kvm_is_dm_lowest_prio() into lapic.h and renamed to
kvm_lowest_prio_delivery().

Changed a check in kvm_irq_delivery_to_apic_fast() from
irq->delivery_mode == APIC_DM_LOWPRI to kvm_is_dm_lowest_prio().

Signed-off-by: James Sullivan <sullivan.james.f@gmail.com>
Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/irq_comm.c

@@ -31,6 +31,8 @@
 
 #include "ioapic.h"
 
+#include "lapic.h"
+
 static int kvm_set_pic_irq(struct kvm_kernel_irq_routing_entry *e,
 			   struct kvm *kvm, int irq_source_id, int level,
 			   bool line_status)
@@ -48,11 +50,6 @@ static int kvm_set_ioapic_irq(struct kvm_kernel_irq_routing_entry *e,
 				line_status);
 }
 
-inline static bool kvm_is_dm_lowest_prio(struct kvm_lapic_irq *irq)
-{
-	return irq->delivery_mode == APIC_DM_LOWEST;
-}
-
 int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
 		struct kvm_lapic_irq *irq, unsigned long *dest_map)
 {
@@ -60,7 +57,7 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
 	struct kvm_vcpu *vcpu, *lowest = NULL;
 
 	if (irq->dest_mode == 0 && irq->dest_id == 0xff &&
-			kvm_is_dm_lowest_prio(irq)) {
+			kvm_lowest_prio_delivery(irq)) {
 		printk(KERN_INFO "kvm: apic: phys broadcast and lowest prio\n");
 		irq->delivery_mode = APIC_DM_FIXED;
 	}
@@ -76,7 +73,7 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
 					irq->dest_id, irq->dest_mode))
 			continue;
 
-		if (!kvm_is_dm_lowest_prio(irq)) {
+		if (!kvm_lowest_prio_delivery(irq)) {
 			if (r < 0)
 				r = 0;
 			r += kvm_apic_set_irq(vcpu, irq, dest_map);

arch/x86/kvm/lapic.c

@@ -728,7 +728,7 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
 
 		dst = map->logical_map[cid];
 
-		if (irq->delivery_mode == APIC_DM_LOWEST) {
+		if (kvm_lowest_prio_delivery(irq)) {
 			int l = -1;
 			for_each_set_bit(i, &bitmap, 16) {
 				if (!dst[i])

arch/x86/kvm/lapic.h

@@ -153,6 +153,12 @@ static inline bool kvm_apic_has_events(struct kvm_vcpu *vcpu)
 	return vcpu->arch.apic->pending_events;
 }
 
+static inline bool kvm_lowest_prio_delivery(struct kvm_lapic_irq *irq)
+{
+	return (irq->delivery_mode == APIC_DM_LOWEST ||
+			irq->msi_redir_hint);
+}
+
 bool kvm_apic_pending_eoi(struct kvm_vcpu *vcpu, int vector);
 
 void wait_lapic_expire(struct kvm_vcpu *vcpu);