diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 09efa9eb3926..e34e51fa28b0 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1482,6 +1482,11 @@ struct kvm_irq_routing_msi {
 	__u32 pad;
 };
 
+On x86, address_hi is ignored unless the KVM_X2APIC_API_USE_32BIT_IDS
+feature of KVM_CAP_X2APIC_API capability is enabled.  If it is enabled,
+address_hi bits 31-8 provide bits 31-8 of the destination id.  Bits 7-0 of
+address_hi must be zero.
+
 struct kvm_irq_routing_s390_adapter {
 	__u64 ind_addr;
 	__u64 summary_addr;
@@ -1583,6 +1588,17 @@ struct kvm_lapic_state {
 Reads the Local APIC registers and copies them into the input argument.  The
 data format and layout are the same as documented in the architecture manual.
 
+If KVM_X2APIC_API_USE_32BIT_IDS feature of KVM_CAP_X2APIC_API is
+enabled, then the format of APIC_ID register depends on the APIC mode
+(reported by MSR_IA32_APICBASE) of its VCPU.  x2APIC stores APIC ID in
+the APIC_ID register (bytes 32-35).  xAPIC only allows an 8-bit APIC ID
+which is stored in bits 31-24 of the APIC register, or equivalently in
+byte 35 of struct kvm_lapic_state's regs field.  KVM_GET_LAPIC must then
+be called after MSR_IA32_APICBASE has been set with KVM_SET_MSR.
+
+If KVM_X2APIC_API_USE_32BIT_IDS feature is disabled, struct kvm_lapic_state
+always uses xAPIC format.
+
 
 4.58 KVM_SET_LAPIC
 
@@ -1600,6 +1616,10 @@ struct kvm_lapic_state {
 Copies the input argument into the Local APIC registers.  The data format
 and layout are the same as documented in the architecture manual.
 
+The format of the APIC ID register (bytes 32-35 of struct kvm_lapic_state's
+regs field) depends on the state of the KVM_CAP_X2APIC_API capability.
+See the note in KVM_GET_LAPIC.
+
 
 4.59 KVM_IOEVENTFD
 
@@ -2180,6 +2200,10 @@ struct kvm_msi {
 
 No flags are defined so far. The corresponding field must be 0.
 
+On x86, address_hi is ignored unless the KVM_CAP_X2APIC_API capability is
+enabled.  If it is enabled, address_hi bits 31-8 provide bits 31-8 of the
+destination id.  Bits 7-0 of address_hi must be zero.
+
 
 4.71 KVM_CREATE_PIT2
 
@@ -3811,6 +3835,23 @@ Allows use of runtime-instrumentation introduced with zEC12 processor.
 Will return -EINVAL if the machine does not support runtime-instrumentation.
 Will return -EBUSY if a VCPU has already been created.
 
+7.7 KVM_CAP_X2APIC_API
+
+Architectures: x86
+Parameters: args[0] - features that should be enabled
+Returns: 0 on success, -EINVAL when args[0] contains invalid features
+
+Valid feature flags in args[0] are
+
+#define KVM_X2APIC_API_USE_32BIT_IDS            (1ULL << 0)
+
+Enabling KVM_X2APIC_API_USE_32BIT_IDS changes the behavior of
+KVM_SET_GSI_ROUTING, KVM_SIGNAL_MSI, KVM_SET_LAPIC, and KVM_GET_LAPIC,
+allowing the use of 32-bit APIC IDs.  See KVM_CAP_X2APIC_API in their
+respective sections.
+
+
+
 8. Other capabilities.
 ----------------------
 
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index a2832cc3cb81..7c00ba3242d7 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -782,6 +782,8 @@ struct kvm_arch {
 	u32 ldr_mode;
 	struct page *avic_logical_id_table_page;
 	struct page *avic_physical_id_table_page;
+
+	bool x2apic_format;
 };
 
 struct kvm_vm_stat {
@@ -1364,7 +1366,7 @@ bool kvm_vcpu_is_bsp(struct kvm_vcpu *vcpu);
 bool kvm_intr_is_single_vcpu(struct kvm *kvm, struct kvm_lapic_irq *irq,
 			     struct kvm_vcpu **dest_vcpu);
 
-void kvm_set_msi_irq(struct kvm_kernel_irq_routing_entry *e,
+void kvm_set_msi_irq(struct kvm *kvm, struct kvm_kernel_irq_routing_entry *e,
 		     struct kvm_lapic_irq *irq);
 
 static inline void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
index 889563d50c55..25810b144b58 100644
--- a/arch/x86/kvm/irq_comm.c
+++ b/arch/x86/kvm/irq_comm.c
@@ -110,13 +110,17 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
 	return r;
 }
 
-void kvm_set_msi_irq(struct kvm_kernel_irq_routing_entry *e,
+void kvm_set_msi_irq(struct kvm *kvm, struct kvm_kernel_irq_routing_entry *e,
 		     struct kvm_lapic_irq *irq)
 {
-	trace_kvm_msi_set_irq(e->msi.address_lo, e->msi.data);
+	trace_kvm_msi_set_irq(e->msi.address_lo | (kvm->arch.x2apic_format ?
+	                                     (u64)e->msi.address_hi << 32 : 0),
+	                      e->msi.data);
 
 	irq->dest_id = (e->msi.address_lo &
 			MSI_ADDR_DEST_ID_MASK) >> MSI_ADDR_DEST_ID_SHIFT;
+	if (kvm->arch.x2apic_format)
+		irq->dest_id |= MSI_ADDR_EXT_DEST_ID(e->msi.address_hi);
 	irq->vector = (e->msi.data &
 			MSI_DATA_VECTOR_MASK) >> MSI_DATA_VECTOR_SHIFT;
 	irq->dest_mode = (1 << MSI_ADDR_DEST_MODE_SHIFT) & e->msi.address_lo;
@@ -129,15 +133,24 @@ void kvm_set_msi_irq(struct kvm_kernel_irq_routing_entry *e,
 }
 EXPORT_SYMBOL_GPL(kvm_set_msi_irq);
 
+static inline bool kvm_msi_route_invalid(struct kvm *kvm,
+		struct kvm_kernel_irq_routing_entry *e)
+{
+	return kvm->arch.x2apic_format && (e->msi.address_hi & 0xff);
+}
+
 int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
 		struct kvm *kvm, int irq_source_id, int level, bool line_status)
 {
 	struct kvm_lapic_irq irq;
 
+	if (kvm_msi_route_invalid(kvm, e))
+		return -EINVAL;
+
 	if (!level)
 		return -1;
 
-	kvm_set_msi_irq(e, &irq);
+	kvm_set_msi_irq(kvm, e, &irq);
 
 	return kvm_irq_delivery_to_apic(kvm, NULL, &irq, NULL);
 }
@@ -153,7 +166,10 @@ int kvm_arch_set_irq_inatomic(struct kvm_kernel_irq_routing_entry *e,
 	if (unlikely(e->type != KVM_IRQ_ROUTING_MSI))
 		return -EWOULDBLOCK;
 
-	kvm_set_msi_irq(e, &irq);
+	if (kvm_msi_route_invalid(kvm, e))
+		return -EINVAL;
+
+	kvm_set_msi_irq(kvm, e, &irq);
 
 	if (kvm_irq_delivery_to_apic_fast(kvm, NULL, &irq, &r, NULL))
 		return r;
@@ -286,6 +302,9 @@ int kvm_set_routing_entry(struct kvm *kvm,
 		e->msi.address_lo = ue->u.msi.address_lo;
 		e->msi.address_hi = ue->u.msi.address_hi;
 		e->msi.data = ue->u.msi.data;
+
+		if (kvm_msi_route_invalid(kvm, e))
+			goto out;
 		break;
 	case KVM_IRQ_ROUTING_HV_SINT:
 		e->set = kvm_hv_set_sint;
@@ -394,7 +413,7 @@ void kvm_scan_ioapic_routes(struct kvm_vcpu *vcpu,
 			if (entry->type != KVM_IRQ_ROUTING_MSI)
 				continue;
 
-			kvm_set_msi_irq(entry, &irq);
+			kvm_set_msi_irq(vcpu->kvm, entry, &irq);
 
 			if (irq.level && kvm_apic_match_dest(vcpu, NULL, 0,
 						irq.dest_id, irq.dest_mode))
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 3c2a8c113054..d27a7829a4ce 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1991,10 +1991,15 @@ static int kvm_apic_state_fixup(struct kvm_vcpu *vcpu,
 	if (apic_x2apic_mode(vcpu->arch.apic)) {
 		u32 *id = (u32 *)(s->regs + APIC_ID);
 
-		if (set)
-			*id >>= 24;
-		else
-			*id <<= 24;
+		if (vcpu->kvm->arch.x2apic_format) {
+			if (*id != vcpu->vcpu_id)
+				return -EINVAL;
+		} else {
+			if (set)
+				*id >>= 24;
+			else
+				*id <<= 24;
+		}
 	}
 
 	return 0;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 7bdd6b1a2373..b61cdadf8623 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -11104,7 +11104,7 @@ static int vmx_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
 		 * We will support full lowest-priority interrupt later.
 		 */
 
-		kvm_set_msi_irq(e, &irq);
+		kvm_set_msi_irq(kvm, e, &irq);
 		if (!kvm_intr_is_single_vcpu(kvm, &irq, &vcpu)) {
 			/*
 			 * Make sure the IRTE is in remapped mode if
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b6e402d16e0c..d86f563a6896 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -90,6 +90,8 @@ static u64 __read_mostly efer_reserved_bits = ~((u64)EFER_SCE);
 #define VM_STAT(x) offsetof(struct kvm, stat.x), KVM_STAT_VM
 #define VCPU_STAT(x) offsetof(struct kvm_vcpu, stat.x), KVM_STAT_VCPU
 
+#define KVM_X2APIC_API_VALID_FLAGS (KVM_X2APIC_API_USE_32BIT_IDS)
+
 static void update_cr8_intercept(struct kvm_vcpu *vcpu);
 static void process_nmi(struct kvm_vcpu *vcpu);
 static void enter_smm(struct kvm_vcpu *vcpu);
@@ -2625,6 +2627,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_TSC_CONTROL:
 		r = kvm_has_tsc_control;
 		break;
+	case KVM_CAP_X2APIC_API:
+		r = KVM_X2APIC_API_VALID_FLAGS;
+		break;
 	default:
 		r = 0;
 		break;
@@ -3799,6 +3804,16 @@ split_irqchip_unlock:
 		mutex_unlock(&kvm->lock);
 		break;
 	}
+	case KVM_CAP_X2APIC_API:
+		r = -EINVAL;
+		if (cap->args[0] & ~KVM_X2APIC_API_VALID_FLAGS)
+			break;
+
+		if (cap->args[0] & KVM_X2APIC_API_USE_32BIT_IDS)
+			kvm->arch.x2apic_format = true;
+
+		r = 0;
+		break;
 	default:
 		r = -EINVAL;
 		break;
diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
index f28292d73ddb..8ade3eb6c640 100644
--- a/include/trace/events/kvm.h
+++ b/include/trace/events/kvm.h
@@ -151,8 +151,9 @@ TRACE_EVENT(kvm_msi_set_irq,
 		__entry->data		= data;
 	),
 
-	TP_printk("dst %u vec %u (%s|%s|%s%s)",
-		  (u8)(__entry->address >> 12), (u8)__entry->data,
+	TP_printk("dst %llx vec %u (%s|%s|%s%s)",
+		  (u8)(__entry->address >> 12) | ((__entry->address >> 32) & 0xffffff00),
+		  (u8)__entry->data,
 		  __print_symbolic((__entry->data >> 8 & 0x7), kvm_deliver_mode),
 		  (__entry->address & (1<<2)) ? "logical" : "physical",
 		  (__entry->data & (1<<15)) ? "level" : "edge",
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 05ebf475104c..f704403e19a0 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -866,6 +866,7 @@ struct kvm_ppc_smmu_info {
 #define KVM_CAP_ARM_PMU_V3 126
 #define KVM_CAP_VCPU_ATTRIBUTES 127
 #define KVM_CAP_MAX_VCPU_ID 128
+#define KVM_CAP_X2APIC_API 129
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -1313,4 +1314,6 @@ struct kvm_assigned_msix_entry {
 	__u16 padding[3];
 };
 
+#define KVM_X2APIC_API_USE_32BIT_IDS            (1ULL << 0)
+
 #endif /* __LINUX_KVM_H */