[PATCH 7/8] KVM: x86: avoid logical_map when it is invalid

["Radim Krčmář" <rkrcmar@redhat.com>]

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>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/lapic.c            | 16 ++++++++++++++++
 arch/x86/kvm/lapic.h            |  4 ++++
 3 files changed, 21 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 26d0f0f646d3..fec3188cabbb 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -554,6 +554,7 @@ struct kvm_arch_memory_slot {
 
 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 fab007509047..621d9df6ac63 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -162,16 +162,19 @@ 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 +204,13 @@ static void recalculate_apic_map(struct kvm *kvm)
 
 		if (aid < ARRAY_SIZE(new->phys_map))
 			new->phys_map[aid] = apic;
+
+		/* The logical map is definitely wrong if we have multiple
+		 * modes at the same time.  Physical is still right though.
+		 */
+		if (hweight8(new->mode) != 1)
+			continue;
+
 		if (lid && cid < ARRAY_SIZE(new->logical_map))
 			new->logical_map[cid][ffs(lid) - 1] = apic;
 	}
@@ -720,6 +730,12 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
 		if (cid >= ARRAY_SIZE(map->logical_map))
 			goto out;
 
+		if (hweight8(map->mode) != 1) {
+			/* Not deliverable with optimized map. */
+			ret = false;
+			goto out;
+		}
+
 		dst = map->logical_map[cid];
 
 		bitmap = apic_logical_id(map, mda);
diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index c1ef25c89508..fd0197a93862 100644
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -8,6 +8,10 @@
 #define KVM_APIC_INIT		0
 #define KVM_APIC_SIPI		1
 
+#define KVM_APIC_MODE_XAPIC_FLAT            (1 << 0)
+#define KVM_APIC_MODE_XAPIC_CLUSTER         (1 << 1)
+#define KVM_APIC_MODE_X2APIC                (1 << 2)
+
 struct kvm_timer {
 	struct hrtimer timer;
 	s64 period; 				/* unit: ns */
-- 
2.2.2