KVM: x86: fix mixed APIC mode broadcast

Broadcast allowed only one global APIC mode, but mixed modes are
theoretically possible.  x2APIC IPI doesn't mean 0xff as broadcast,
the rest does.

x2APIC broadcasts are accepted by xAPIC.  If we take SDM to be logical,
even addreses beginning with 0xff should be accepted, but real hardware
disagrees.  This patch aims for simple code by considering most of real
behavior as undefined.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Message-Id: <1423766494-26150-3-git-send-email-rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -552,7 +552,7 @@ struct kvm_apic_map {
 	struct rcu_head rcu;
 	u8 ldr_bits;
 	/* fields bellow are used to decode ldr values in different modes */
-	u32 cid_shift, cid_mask, lid_mask, broadcast;
+	u32 cid_shift, cid_mask, lid_mask;
 	struct kvm_lapic *phys_map[256];
 	/* first index is cluster id second is cpu id in a cluster */
 	struct kvm_lapic *logical_map[16][16];

arch/x86/kvm/lapic.c

@@ -151,7 +151,6 @@ static void recalculate_apic_map(struct kvm *kvm)
 	new->cid_shift = 8;
 	new->cid_mask = 0;
 	new->lid_mask = 0xff;
-	new->broadcast = APIC_BROADCAST;
 
 	kvm_for_each_vcpu(i, vcpu, kvm) {
 		struct kvm_lapic *apic = vcpu->arch.apic;
@@ -163,7 +162,6 @@ static void recalculate_apic_map(struct kvm *kvm)
 			new->ldr_bits = 32;
 			new->cid_shift = 16;
 			new->cid_mask = new->lid_mask = 0xffff;
-			new->broadcast = X2APIC_BROADCAST;
 		} else if (kvm_apic_get_reg(apic, APIC_LDR)) {
 			if (kvm_apic_get_reg(apic, APIC_DFR) ==
 							APIC_DFR_CLUSTER) {
@@ -690,6 +688,7 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
 	struct kvm_lapic **dst;
 	int i;
 	bool ret = false;
+	bool x2apic_ipi = src && apic_x2apic_mode(src);
 
 	*r = -1;
 
@@ -701,15 +700,15 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
 	if (irq->shorthand)
 		return false;
 
+	if (irq->dest_id == (x2apic_ipi ? X2APIC_BROADCAST : APIC_BROADCAST))
+		return false;
+
 	rcu_read_lock();
 	map = rcu_dereference(kvm->arch.apic_map);
 
 	if (!map)
 		goto out;
 
-	if (irq->dest_id == map->broadcast)
-		goto out;
-
 	ret = true;
 
 	if (irq->dest_mode == APIC_DEST_PHYSICAL) {