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>

1 files changed, 4 insertions, 5 deletions

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 69569744745d..d45f00ba7440 100644
--- a/arch/x86/kvm/lapic.c
+++ b/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) {