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>
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 5b1bc97..9477b27 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -548,8 +548,20 @@
struct kvm_lpage_info *lpage_info[KVM_NR_PAGE_SIZES - 1];
};
+/*
+ * We use as the mode the number of bits allocated in the LDR for the
+ * logical processor ID. It happens that these are all powers of two.
+ * This makes it is very easy to detect cases where the APICs are
+ * configured for multiple modes; in that case, we cannot use the map and
+ * hence cannot use kvm_irq_delivery_to_apic_fast either.
+ */
+#define KVM_APIC_MODE_XAPIC_CLUSTER 4
+#define KVM_APIC_MODE_XAPIC_FLAT 8
+#define KVM_APIC_MODE_X2APIC 16
+
struct kvm_apic_map {
struct rcu_head rcu;
+ u8 mode;
u8 ldr_bits;
/* fields bellow are used to decode ldr values in different modes */
u32 cid_shift, cid_mask, lid_mask;
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index d45f00b..fa4bd89 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -133,6 +133,14 @@
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 @@
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 @@
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 @@
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;