diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index aa75f21..4a390a4 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -635,6 +635,7 @@ enum emulation_result {
 	EMULATE_DONE,       /* no further processing */
 	EMULATE_DO_MMIO,      /* kvm_run filled with mmio request */
 	EMULATE_FAIL,         /* can't emulate this instruction */
+	EMULATE_USERSPACE_EXIT, /* we need exit to userspace */
 };
 
 #define EMULTYPE_NO_DECODE	    (1 << 0)
diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index f15501f..3a0d851 100644
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile
@@ -7,7 +7,7 @@ CFLAGS_vmx.o := -I.
 
 kvm-y			+= $(addprefix ../../../virt/kvm/, kvm_main.o ioapic.o \
 				coalesced_mmio.o irq_comm.o eventfd.o \
-				assigned-dev.o)
+				assigned-dev.o msix_mmio.o)
 kvm-$(CONFIG_IOMMU_API)	+= $(addprefix ../../../virt/kvm/, iommu.o)
 kvm-$(CONFIG_KVM_ASYNC_PF)	+= $(addprefix ../../../virt/kvm/, async_pf.o)
 
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 9cafbb4..912dca4 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3358,6 +3358,8 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code,
 	case EMULATE_DO_MMIO:
 		++vcpu->stat.mmio_exits;
 		/* fall through */
+	case EMULATE_USERSPACE_EXIT:
+		/* fall through */
 	case EMULATE_FAIL:
 		return 0;
 	default:
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 21b84e2..87308eb 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1966,6 +1966,7 @@ int kvm_dev_ioctl_check_extension(long ext)
 	case KVM_CAP_X86_ROBUST_SINGLESTEP:
 	case KVM_CAP_XSAVE:
 	case KVM_CAP_ASYNC_PF:
+	case KVM_CAP_MSIX_MMIO:
 		r = 1;
 		break;
 	case KVM_CAP_COALESCED_MMIO:
@@ -3809,6 +3810,7 @@ static int emulator_write_emulated_onepage(unsigned long addr,
 {
 	gpa_t                 gpa;
 	struct kvm_io_ext_data ext_data;
+	int r;
 
 	gpa = kvm_mmu_gva_to_gpa_write(vcpu, addr, exception);
 
@@ -3824,18 +3826,32 @@ static int emulator_write_emulated_onepage(unsigned long addr,
 
 mmio:
 	trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, bytes, gpa, *(u64 *)val);
+	r = vcpu_mmio_write(vcpu, gpa, bytes, val, &ext_data);
 	/*
 	 * Is this MMIO handled locally?
 	 */
-	if (!vcpu_mmio_write(vcpu, gpa, bytes, val, &ext_data))
+	if (!r)
 		return X86EMUL_CONTINUE;
 
-	vcpu->mmio_needed = 1;
-	vcpu->run->exit_reason = KVM_EXIT_MMIO;
-	vcpu->run->mmio.phys_addr = vcpu->mmio_phys_addr = gpa;
-	vcpu->run->mmio.len = vcpu->mmio_size = bytes;
-	vcpu->run->mmio.is_write = vcpu->mmio_is_write = 1;
-	memcpy(vcpu->run->mmio.data, val, bytes);
+	if (r == -ENOTSYNC) {
+		vcpu->userspace_exit_needed = 1;
+		vcpu->run->exit_reason = KVM_EXIT_MSIX_ROUTING_UPDATE;
+		vcpu->run->msix_routing.dev_id =
+			ext_data.msix_routing.dev_id;
+		vcpu->run->msix_routing.type =
+			ext_data.msix_routing.type;
+		vcpu->run->msix_routing.entry_idx =
+			ext_data.msix_routing.entry_idx;
+		vcpu->run->msix_routing.flags =
+			ext_data.msix_routing.flags;
+	} else  {
+		vcpu->mmio_needed = 1;
+		vcpu->run->exit_reason = KVM_EXIT_MMIO;
+		vcpu->run->mmio.phys_addr = vcpu->mmio_phys_addr = gpa;
+		vcpu->run->mmio.len = vcpu->mmio_size = bytes;
+		vcpu->run->mmio.is_write = vcpu->mmio_is_write = 1;
+		memcpy(vcpu->run->mmio.data, val, bytes);
+	}
 
 	return X86EMUL_CONTINUE;
 }
@@ -4469,6 +4485,8 @@ done:
 		r = EMULATE_DO_MMIO;
 	} else if (r == EMULATION_RESTART)
 		goto restart;
+	else if (vcpu->userspace_exit_needed)
+		r = EMULATE_USERSPACE_EXIT;
 	else
 		r = EMULATE_DONE;
 
@@ -5397,12 +5415,18 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 		}
 	}
 
-	if (vcpu->arch.pio.count || vcpu->mmio_needed) {
+	if (vcpu->arch.pio.count || vcpu->mmio_needed ||
+			vcpu->userspace_exit_needed) {
 		if (vcpu->mmio_needed) {
 			memcpy(vcpu->mmio_data, kvm_run->mmio.data, 8);
 			vcpu->mmio_read_completed = 1;
 			vcpu->mmio_needed = 0;
 		}
+		if (vcpu->userspace_exit_needed) {
+			vcpu->userspace_exit_needed = 0;
+			r = 0;
+			goto out;
+		}
 		vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
 		r = emulate_instruction(vcpu, EMULTYPE_NO_DECODE);
 		srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index ea2dc1a..4393e4e 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -161,6 +161,7 @@ struct kvm_pit_config {
 #define KVM_EXIT_NMI              16
 #define KVM_EXIT_INTERNAL_ERROR   17
 #define KVM_EXIT_OSI              18
+#define KVM_EXIT_MSIX_ROUTING_UPDATE 19
 
 /* For KVM_EXIT_INTERNAL_ERROR */
 #define KVM_INTERNAL_ERROR_EMULATION 1
@@ -264,6 +265,13 @@ struct kvm_run {
 		struct {
 			__u64 gprs[32];
 		} osi;
+		/* KVM_EXIT_MSIX_ROUTING_UPDATE*/
+		struct {
+			__u32 dev_id;
+			__u16 type;
+			__u16 entry_idx;
+			__u64 flags;
+		} msix_routing;
 		/* Fix the size of the union. */
 		char padding[256];
 	};
@@ -541,6 +549,7 @@ struct kvm_ppc_pvinfo {
 #define KVM_CAP_PPC_GET_PVINFO 57
 #define KVM_CAP_PPC_IRQ_LEVEL 58
 #define KVM_CAP_ASYNC_PF 59
+#define KVM_CAP_MSIX_MMIO 60
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -672,6 +681,9 @@ struct kvm_clock_data {
 #define KVM_XEN_HVM_CONFIG        _IOW(KVMIO,  0x7a, struct kvm_xen_hvm_config)
 #define KVM_SET_CLOCK             _IOW(KVMIO,  0x7b, struct kvm_clock_data)
 #define KVM_GET_CLOCK             _IOR(KVMIO,  0x7c, struct kvm_clock_data)
+/* Available with KVM_CAP_MSIX_MMIO */
+#define KVM_REGISTER_MSIX_MMIO    _IOW(KVMIO,  0x7d, struct kvm_msix_mmio_user)
+#define KVM_UNREGISTER_MSIX_MMIO  _IOW(KVMIO,  0x7e, struct kvm_msix_mmio_user)
 /* Available with KVM_CAP_PIT_STATE2 */
 #define KVM_GET_PIT2              _IOR(KVMIO,  0x9f, struct kvm_pit_state2)
 #define KVM_SET_PIT2              _IOW(KVMIO,  0xa0, struct kvm_pit_state2)
@@ -795,4 +807,20 @@ struct kvm_assigned_msix_entry {
 	__u16 padding[3];
 };
 
+#define KVM_MSIX_MMIO_TYPE_ASSIGNED_DEV	    (1 << 0)
+
+#define KVM_MSIX_MMIO_TYPE_BASE_TABLE	    (1 << 8)
+
+#define KVM_MSIX_MMIO_TYPE_DEV_MASK	    0x00ff
+#define KVM_MSIX_MMIO_TYPE_BASE_MASK	    0xff00
+struct kvm_msix_mmio_user {
+	__u32 dev_id;
+	__u16 type;
+	__u16 max_entries_nr;
+	__u64 base_addr;
+	__u64 base_va;
+	__u64 flags;
+	__u64 reserved[4];
+};
+
 #endif /* __LINUX_KVM_H */
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 6bb211d..6aaf85e 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -68,9 +68,16 @@ enum kvm_bus {
 	KVM_NR_BUSES
 };
 
+#define KVM_IO_EXT_DATA_TYPE_MSIX_ROUTING   1
 struct kvm_io_ext_data {
 	int type;
 	union {
+		struct {
+			u32 dev_id;
+			u16 type;
+			u16 entry_idx;
+			u64 flags;
+		} msix_routing;
 		char padding[256];
 	};
 };
@@ -168,6 +175,8 @@ struct kvm_vcpu {
 	} async_pf;
 #endif
 
+	int userspace_exit_needed;
+
 	struct kvm_vcpu_arch arch;
 };
 
@@ -241,6 +250,27 @@ struct kvm_memslots {
 					KVM_PRIVATE_MEM_SLOTS];
 };
 
+#define KVM_MSIX_MMIO_MAX    32
+
+struct kvm_msix_mmio {
+	u32 dev_id;
+	u16 type;
+	u16 max_entries_nr;
+	u64 flags;
+	gpa_t table_base_addr;
+	hva_t table_base_va;
+	gpa_t pba_base_addr;
+	hva_t pba_base_va;
+};
+
+struct kvm_msix_mmio_dev {
+	struct kvm *kvm;
+	struct kvm_io_device table_dev;
+	int mmio_nr;
+	struct kvm_msix_mmio mmio[KVM_MSIX_MMIO_MAX];
+	struct mutex lock;
+};
+
 struct kvm {
 	spinlock_t mmu_lock;
 	raw_spinlock_t requests_lock;
@@ -289,6 +319,7 @@ struct kvm {
 	long mmu_notifier_count;
 #endif
 	long tlbs_dirty;
+	struct kvm_msix_mmio_dev msix_mmio_dev;
 };
 
 /* The guest did something we don't support. */
@@ -561,6 +592,9 @@ void kvm_unregister_irq_ack_notifier(struct kvm *kvm,
 int kvm_request_irq_source_id(struct kvm *kvm);
 void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id);
 
+int kvm_assigned_device_update_msix_mask_bit(struct kvm *kvm,
+			int assigned_dev_id, int entry, bool mask);
+
 /* For vcpu->arch.iommu_flags */
 #define KVM_IOMMU_CACHE_COHERENCY	0x1
 
diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c
index ae72ae6..d1598a6 100644
--- a/virt/kvm/assigned-dev.c
+++ b/virt/kvm/assigned-dev.c
@@ -18,6 +18,7 @@
 #include <linux/interrupt.h>
 #include <linux/slab.h>
 #include "irq.h"
+#include "msix_mmio.h"
 
 static struct kvm_assigned_dev_kernel *kvm_find_assigned_dev(struct list_head *head,
 						      int assigned_dev_id)
@@ -191,12 +192,25 @@ static void kvm_free_assigned_irq(struct kvm *kvm,
 	kvm_deassign_irq(kvm, assigned_dev, assigned_dev->irq_requested_type);
 }
 
+static void assigned_device_free_msix_mmio(struct kvm *kvm,
+				struct kvm_assigned_dev_kernel *adev)
+{
+	struct kvm_msix_mmio mmio;
+
+	mmio.dev_id = adev->assigned_dev_id;
+	mmio.type = KVM_MSIX_MMIO_TYPE_ASSIGNED_DEV |
+		    KVM_MSIX_MMIO_TYPE_BASE_TABLE;
+	kvm_free_msix_mmio(kvm, &mmio);
+}
+
 static void kvm_free_assigned_device(struct kvm *kvm,
 				     struct kvm_assigned_dev_kernel
 				     *assigned_dev)
 {
 	kvm_free_assigned_irq(kvm, assigned_dev);
 
+	assigned_device_free_msix_mmio(kvm, assigned_dev);
+
 	__pci_reset_function(assigned_dev->dev);
 	pci_restore_state(assigned_dev->dev);
 
@@ -785,3 +799,33 @@ out:
 	return r;
 }
 
+/* The caller should hold kvm->lock */
+int kvm_assigned_device_update_msix_mask_bit(struct kvm *kvm,
+				int assigned_dev_id, int entry, bool mask)
+{
+	int r = -EFAULT;
+	struct kvm_assigned_dev_kernel *adev;
+	int i;
+
+	if (!irqchip_in_kernel(kvm))
+		return r;
+
+	adev = kvm_find_assigned_dev(&kvm->arch.assigned_dev_head,
+				      assigned_dev_id);
+	if (!adev)
+		goto out;
+
+	/* For non-MSIX enabled devices, entries_nr == 0 */
+	for (i = 0; i < adev->entries_nr; i++)
+		if (adev->host_msix_entries[i].entry == entry) {
+			if (mask)
+				disable_irq_nosync(
+					adev->host_msix_entries[i].vector);
+			else
+				enable_irq(adev->host_msix_entries[i].vector);
+			r = 0;
+			break;
+		}
+out:
+	return r;
+}
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index a61f90e..f211e49 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -56,6 +56,7 @@
 
 #include "coalesced_mmio.h"
 #include "async_pf.h"
+#include "msix_mmio.h"
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/kvm.h>
@@ -509,6 +510,7 @@ static void kvm_destroy_vm(struct kvm *kvm)
 	struct mm_struct *mm = kvm->mm;
 
 	kvm_arch_sync_events(kvm);
+	kvm_unregister_msix_mmio_dev(kvm);
 	spin_lock(&kvm_lock);
 	list_del(&kvm->vm_list);
 	spin_unlock(&kvm_lock);
@@ -1877,6 +1879,24 @@ static long kvm_vm_ioctl(struct file *filp,
 		mutex_unlock(&kvm->lock);
 		break;
 #endif
+	case KVM_REGISTER_MSIX_MMIO: {
+		struct kvm_msix_mmio_user mmio_user;
+
+		r = -EFAULT;
+		if (copy_from_user(&mmio_user, argp, sizeof mmio_user))
+			goto out;
+		r = kvm_vm_ioctl_register_msix_mmio(kvm, &mmio_user);
+		break;
+	}
+	case KVM_UNREGISTER_MSIX_MMIO: {
+		struct kvm_msix_mmio_user mmio_user;
+
+		r = -EFAULT;
+		if (copy_from_user(&mmio_user, argp, sizeof mmio_user))
+			goto out;
+		r = kvm_vm_ioctl_unregister_msix_mmio(kvm, &mmio_user);
+		break;
+	}
 	default:
 		r = kvm_arch_vm_ioctl(filp, ioctl, arg);
 		if (r == -ENOTTY)
@@ -1988,6 +2008,12 @@ static int kvm_dev_ioctl_create_vm(void)
 		return r;
 	}
 #endif
+	r = kvm_register_msix_mmio_dev(kvm);
+	if (r < 0) {
+		kvm_put_kvm(kvm);
+		return r;
+	}
+
 	r = anon_inode_getfd("kvm-vm", &kvm_vm_fops, kvm, O_RDWR);
 	if (r < 0)
 		kvm_put_kvm(kvm);
@@ -2223,14 +2249,18 @@ static void kvm_io_bus_destroy(struct kvm_io_bus *bus)
 int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
 		     int len, const void *val, struct kvm_io_ext_data *ext_data)
 {
-	int i;
+	int i, r = -EOPNOTSUPP;
 	struct kvm_io_bus *bus;
 
 	bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
-	for (i = 0; i < bus->dev_count; i++)
-		if (!kvm_iodevice_write(bus->devs[i], addr, len, val, ext_data))
+	for (i = 0; i < bus->dev_count; i++) {
+		r = kvm_iodevice_write(bus->devs[i], addr, len, val, ext_data);
+		if (r == -ENOTSYNC)
+			break;
+		else if (!r)
 			return 0;
-	return -EOPNOTSUPP;
+	}
+	return r;
 }
 
 /* kvm_io_bus_read - called under kvm->slots_lock */
diff --git a/virt/kvm/msix_mmio.c b/virt/kvm/msix_mmio.c
new file mode 100644
index 0000000..4a9cf15
--- /dev/null
+++ b/virt/kvm/msix_mmio.c
@@ -0,0 +1,302 @@
+/*
+ * MSI-X MMIO emulation
+ *
+ * Copyright (c) 2010 Intel Corporation
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ * Author:
+ *   Sheng Yang <sheng.yang@intel.com>
+ */
+
+#include <linux/kvm_host.h>
+#include <linux/kvm.h>
+
+#include "msix_mmio.h"
+#include "iodev.h"
+
+static int update_msix_mask_bit(struct kvm *kvm, struct kvm_msix_mmio *mmio,
+				int entry, u32 flag)
+{
+	if (mmio->type & KVM_MSIX_MMIO_TYPE_ASSIGNED_DEV)
+		return kvm_assigned_device_update_msix_mask_bit(kvm,
+				mmio->dev_id, entry, flag);
+	return -EFAULT;
+}
+
+/* Caller must hold dev->lock */
+static int get_mmio_table_index(struct kvm_msix_mmio_dev *dev,
+				gpa_t addr, int len)
+{
+	gpa_t start, end;
+	int i, r = -EINVAL;
+
+	for (i = 0; i < dev->mmio_nr; i++) {
+		start = dev->mmio[i].table_base_addr;
+		end = dev->mmio[i].table_base_addr + PCI_MSIX_ENTRY_SIZE *
+			dev->mmio[i].max_entries_nr;
+		if (addr >= start && addr + len <= end) {
+			r = i;
+			break;
+		}
+	}
+
+	return r;
+}
+
+static int msix_table_mmio_read(struct kvm_io_device *this, gpa_t addr, int len,
+				void *val)
+{
+	/*TODO: Add big endian support */
+	struct kvm_msix_mmio_dev *mmio_dev =
+		container_of(this, struct kvm_msix_mmio_dev, table_dev);
+	struct kvm_msix_mmio *mmio;
+	int idx, ret = 0, entry, offset, r;
+
+	mutex_lock(&mmio_dev->lock);
+	idx = get_mmio_table_index(mmio_dev, addr, len);
+	if (idx < 0) {
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+	if (!(len == 4 || len == 8) || addr & (len - 1))
+		goto out;
+
+	offset = addr % PCI_MSIX_ENTRY_SIZE;
+	mmio = &mmio_dev->mmio[idx];
+	entry = (addr - mmio->table_base_addr) / PCI_MSIX_ENTRY_SIZE;
+	r = copy_from_user(val, (void __user *)(mmio->table_base_va +
+			entry * PCI_MSIX_ENTRY_SIZE + offset), len);
+	if (r)
+		goto out;
+out:
+	mutex_unlock(&mmio_dev->lock);
+	return ret;
+}
+
+static int msix_table_mmio_write(struct kvm_io_device *this, gpa_t addr,
+				int len, const void *val,
+				struct kvm_io_ext_data *ext_data)
+{
+	/*TODO: Add big endian support */
+	struct kvm_msix_mmio_dev *mmio_dev =
+		container_of(this, struct kvm_msix_mmio_dev, table_dev);
+	struct kvm_msix_mmio *mmio;
+	int idx, entry, offset, ret = 0, r = 0;
+	void __user *entry_base;
+	u32 __user *ctrl_pos;
+	u32 old_ctrl, new_ctrl;
+
+	mutex_lock(&mmio_dev->kvm->lock);
+	mutex_lock(&mmio_dev->lock);
+	idx = get_mmio_table_index(mmio_dev, addr, len);
+	if (idx < 0) {
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+	if (!(len == 4 || len == 8) || addr & (len - 1))
+		goto out;
+
+	offset = addr % PCI_MSIX_ENTRY_SIZE;
+
+	mmio = &mmio_dev->mmio[idx];
+	entry = (addr - mmio->table_base_addr) / PCI_MSIX_ENTRY_SIZE;
+	entry_base = (void __user *)(mmio->table_base_va +
+			entry * PCI_MSIX_ENTRY_SIZE);
+	ctrl_pos = entry_base +
+			PCI_MSIX_ENTRY_VECTOR_CTRL;
+
+	if (get_user(old_ctrl, ctrl_pos))
+		goto out;
+
+	/* Don't allow writing to other fields when entry is unmasked */
+	if (!(old_ctrl & PCI_MSIX_ENTRY_CTRL_MASKBIT) &&
+	    offset != PCI_MSIX_ENTRY_VECTOR_CTRL)
+		goto out;
+
+	if (copy_to_user((void __user *)(entry_base + offset), val, len))
+		goto out;
+
+	ext_data->type = KVM_IO_EXT_DATA_TYPE_MSIX_ROUTING;
+	ext_data->msix_routing.dev_id = mmio->dev_id;
+	ext_data->msix_routing.type = mmio->type;
+	ext_data->msix_routing.entry_idx = entry;
+	ext_data->msix_routing.flags = 0;
+
+	if (offset + len < PCI_MSIX_ENTRY_VECTOR_CTRL) {
+		ret = -ENOTSYNC;
+		goto out;
+	}
+
+	if (get_user(new_ctrl, ctrl_pos))
+		goto out;
+
+	if (old_ctrl == new_ctrl) {
+		if (offset == PCI_MSIX_ENTRY_DATA && len == 8)
+			ret = -ENOTSYNC;
+		goto out;
+	}
+	if ((old_ctrl & PCI_MSIX_ENTRY_CTRL_MASKBIT) ^
+			(new_ctrl & PCI_MSIX_ENTRY_CTRL_MASKBIT))
+		r = update_msix_mask_bit(mmio_dev->kvm, mmio, entry,
+				!!(new_ctrl & PCI_MSIX_ENTRY_CTRL_MASKBIT));
+	if (r)
+		ret = -ENOTSYNC;
+out:
+	mutex_unlock(&mmio_dev->lock);
+	mutex_unlock(&mmio_dev->kvm->lock);
+	return ret;
+}
+
+static const struct kvm_io_device_ops msix_mmio_table_ops = {
+	.read     = msix_table_mmio_read,
+	.write    = msix_table_mmio_write,
+};
+
+int kvm_register_msix_mmio_dev(struct kvm *kvm)
+{
+	int ret;
+
+	kvm_iodevice_init(&kvm->msix_mmio_dev.table_dev, &msix_mmio_table_ops);
+	mutex_init(&kvm->msix_mmio_dev.lock);
+	kvm->msix_mmio_dev.kvm = kvm;
+	mutex_lock(&kvm->slots_lock);
+	ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS,
+				      &kvm->msix_mmio_dev.table_dev);
+	mutex_unlock(&kvm->slots_lock);
+	return ret;
+}
+
+int kvm_unregister_msix_mmio_dev(struct kvm *kvm)
+{
+	int ret;
+
+	mutex_lock(&kvm->slots_lock);
+	ret = kvm_io_bus_unregister_dev(kvm, KVM_MMIO_BUS,
+				      &kvm->msix_mmio_dev.table_dev);
+	mutex_unlock(&kvm->slots_lock);
+	return ret;
+}
+
+int kvm_vm_ioctl_register_msix_mmio(struct kvm *kvm,
+				    struct kvm_msix_mmio_user *mmio_user)
+{
+	struct kvm_msix_mmio_dev *mmio_dev = &kvm->msix_mmio_dev;
+	struct kvm_msix_mmio *mmio = NULL;
+	int r = 0, i;
+
+	mutex_lock(&mmio_dev->lock);
+	for (i = 0; i < mmio_dev->mmio_nr; i++) {
+		if (mmio_dev->mmio[i].dev_id == mmio_user->dev_id &&
+		    (mmio_dev->mmio[i].type & KVM_MSIX_MMIO_TYPE_DEV_MASK) ==
+		    (mmio_user->type & KVM_MSIX_MMIO_TYPE_DEV_MASK)) {
+			mmio = &mmio_dev->mmio[i];
+			if (mmio->max_entries_nr != mmio_user->max_entries_nr) {
+				r = -EINVAL;
+				goto out;
+			}
+			break;
+		}
+	}
+	if (mmio_user->max_entries_nr > KVM_MAX_MSIX_PER_DEV) {
+		r = -EINVAL;
+		goto out;
+	}
+	/* All reserved currently */
+	if (mmio_user->flags) {
+		r = -EINVAL;
+		goto out;
+	}
+
+	if ((mmio_user->type & KVM_MSIX_MMIO_TYPE_DEV_MASK) !=
+			KVM_MSIX_MMIO_TYPE_ASSIGNED_DEV) {
+		r = -EINVAL;
+		goto out;
+	}
+	if ((mmio_user->type & KVM_MSIX_MMIO_TYPE_BASE_MASK) !=
+			KVM_MSIX_MMIO_TYPE_BASE_TABLE) {
+		r = -EINVAL;
+		goto out;
+	}
+
+#ifndef CONFIG_64BIT
+	if (mmio_user->base_va >= 0xffffffff ||
+	    mmio_user->base_addr >= 0xffffffff) {
+		r = -EINVAL;
+		goto out;
+	}
+#endif
+
+	/* Check alignment and accessibility */
+	if ((mmio_user->base_va % PCI_MSIX_ENTRY_SIZE) ||
+	    !access_ok(VERIFY_WRITE, (void __user *)mmio_user->base_va,
+			mmio_user->max_entries_nr * PCI_MSIX_ENTRY_SIZE)) {
+		r = -EINVAL;
+		goto out;
+	}
+	if (!mmio) {
+		if (mmio_dev->mmio_nr == KVM_MSIX_MMIO_MAX) {
+			r = -ENOSPC;
+			goto out;
+		}
+		mmio = &mmio_dev->mmio[mmio_dev->mmio_nr];
+		mmio_dev->mmio_nr++;
+	}
+
+	mmio->max_entries_nr = mmio_user->max_entries_nr;
+	mmio->dev_id = mmio_user->dev_id;
+	mmio->flags = mmio_user->flags;
+
+	if ((mmio_user->type & KVM_MSIX_MMIO_TYPE_DEV_MASK) ==
+			KVM_MSIX_MMIO_TYPE_ASSIGNED_DEV)
+		mmio->type = KVM_MSIX_MMIO_TYPE_ASSIGNED_DEV;
+	if ((mmio_user->type & KVM_MSIX_MMIO_TYPE_BASE_MASK) ==
+			KVM_MSIX_MMIO_TYPE_BASE_TABLE) {
+		mmio->type |= KVM_MSIX_MMIO_TYPE_BASE_TABLE;
+		mmio->table_base_addr = mmio_user->base_addr;
+		mmio->table_base_va = mmio_user->base_va;
+	}
+out:
+	mutex_unlock(&mmio_dev->lock);
+	return r;
+}
+
+int kvm_free_msix_mmio(struct kvm *kvm, struct kvm_msix_mmio *mmio)
+{
+	struct kvm_msix_mmio_dev *mmio_dev = &kvm->msix_mmio_dev;
+	int r = -EINVAL, i, j;
+
+	if (!mmio)
+		return 0;
+
+	mutex_lock(&mmio_dev->lock);
+	BUG_ON(mmio_dev->mmio_nr > KVM_MSIX_MMIO_MAX);
+	for (i = 0; i < mmio_dev->mmio_nr; i++) {
+		if (mmio_dev->mmio[i].dev_id == mmio->dev_id &&
+		    mmio_dev->mmio[i].type == mmio->type) {
+			r = 0;
+			for (j = i; j < mmio_dev->mmio_nr - 1; j++)
+				mmio_dev->mmio[j] = mmio_dev->mmio[j + 1];
+			mmio_dev->mmio[mmio_dev->mmio_nr].max_entries_nr = 0;
+			mmio_dev->mmio[mmio_dev->mmio_nr].dev_id = 0;
+			mmio_dev->mmio[mmio_dev->mmio_nr].type = 0;
+			mmio_dev->mmio_nr--;
+			break;
+		}
+	}
+	mutex_unlock(&mmio_dev->lock);
+	return r;
+}
+
+int kvm_vm_ioctl_unregister_msix_mmio(struct kvm *kvm,
+				      struct kvm_msix_mmio_user *mmio_user)
+{
+	struct kvm_msix_mmio mmio;
+
+	mmio.dev_id = mmio_user->dev_id;
+	mmio.type = mmio_user->type;
+
+	return kvm_free_msix_mmio(kvm, &mmio);
+}
+
diff --git a/virt/kvm/msix_mmio.h b/virt/kvm/msix_mmio.h
new file mode 100644
index 0000000..01b6587
--- /dev/null
+++ b/virt/kvm/msix_mmio.h
@@ -0,0 +1,25 @@
+#ifndef __KVM_MSIX_MMIO_H__
+#define __KVM_MSIX_MMIO_H__
+/*
+ * MSI-X MMIO emulation
+ *
+ * Copyright (c) 2010 Intel Corporation
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ * Author:
+ *   Sheng Yang <sheng.yang@intel.com>
+ */
+
+#include <linux/pci.h>
+
+int kvm_register_msix_mmio_dev(struct kvm *kvm);
+int kvm_unregister_msix_mmio_dev(struct kvm *kvm);
+int kvm_vm_ioctl_register_msix_mmio(struct kvm *kvm,
+				    struct kvm_msix_mmio_user *mmio_user);
+int kvm_vm_ioctl_unregister_msix_mmio(struct kvm *kvm,
+				      struct kvm_msix_mmio_user *mmio_user);
+int kvm_free_msix_mmio(struct kvm *kvm, struct kvm_msix_mmio *mmio_user);
+
+#endif
