KVM: x86: avoid logical_map when it is invalid

We want to support mixed modes and the easiest solution is to avoid
optimizing those weird and unlikely scenarios.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Message-Id: <1423766494-26150-4-git-send-email-rkrcmar@redhat.com>
[Add comment above KVM_APIC_MODE_* defines. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 23 insertions, 1 deletions

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index d45f00ba7440..fa4bd89ea381 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -133,6 +133,14 @@ static inline int kvm_apic_id(struct kvm_lapic *apic)
         return (kvm_apic_get_reg(apic, APIC_ID) >> 24) & 0xff;
 }
 
+/* The logical map is definitely wrong if we have multiple
+ * modes at the same time.  (Physical map is always right.)
+ */
+static inline bool kvm_apic_logical_map_valid(struct kvm_apic_map *map)
+{
+        return !(map->mode & (map->mode - 1));
+}
+
 static void recalculate_apic_map(struct kvm *kvm)
 {
         struct kvm_apic_map *new, *old = NULL;
@@ -162,16 +170,19 @@ static void recalculate_apic_map(struct kvm *kvm)
                         new->ldr_bits = 32;
                         new->cid_shift = 16;
                         new->cid_mask = new->lid_mask = 0xffff;
+                        new->mode |= KVM_APIC_MODE_X2APIC;
                 } else if (kvm_apic_get_reg(apic, APIC_LDR)) {
                         if (kvm_apic_get_reg(apic, APIC_DFR) ==
                                                         APIC_DFR_CLUSTER) {
                                 new->cid_shift = 4;
                                 new->cid_mask = 0xf;
                                 new->lid_mask = 0xf;
+                                new->mode |= KVM_APIC_MODE_XAPIC_CLUSTER;
                         } else {
                                 new->cid_shift = 8;
                                 new->cid_mask = 0;
                                 new->lid_mask = 0xff;
+                                new->mode |= KVM_APIC_MODE_XAPIC_FLAT;
                         }
                 }
 
@@ -201,6 +212,10 @@ static void recalculate_apic_map(struct kvm *kvm)
 
                 if (aid < ARRAY_SIZE(new->phys_map))
                         new->phys_map[aid] = apic;
+
+                if (!kvm_apic_logical_map_valid(new));
+                        continue;
+
                 if (lid && cid < ARRAY_SIZE(new->logical_map))
                         new->logical_map[cid][ffs(lid) - 1] = apic;
         }
@@ -718,7 +733,14 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
                 dst = &map->phys_map[irq->dest_id];
         } else {
                 u32 mda = irq->dest_id << (32 - map->ldr_bits);
-                u16 cid = apic_cluster_id(map, mda);
+                u16 cid;
+
+                if (!kvm_apic_logical_map_valid(map)) {
+                        ret = false;
+                        goto out;
+                }
+
+                cid = apic_cluster_id(map, mda);
 
                 if (cid >= ARRAY_SIZE(map->logical_map))
                         goto out;