diff -r 5c379dcac105 xen/arch/x86/io_apic.c
--- a/xen/arch/x86/io_apic.c	Wed Mar 26 00:51:42 2008 +0800
+++ b/xen/arch/x86/io_apic.c	Wed Mar 26 01:00:18 2008 +0800
@@ -34,6 +34,7 @@
 #include <asm/desc.h>
 #include <mach_apic.h>
 #include <io_ports.h>
+#include <public/physdev.h>
 
 /* Different to Linux: our implementation can be simpler. */
 #define make_8259A_irq(irq) (io_apic_irqs &= ~(1<<(irq)))
@@ -724,6 +725,7 @@ next:
 
 static struct hw_interrupt_type ioapic_level_type;
 static struct hw_interrupt_type ioapic_edge_type;
+struct hw_interrupt_type msi_irq_type;
 
 #define IOAPIC_AUTO	-1
 #define IOAPIC_EDGE	0
@@ -1547,6 +1549,55 @@ static struct hw_interrupt_type ioapic_l
     .set_affinity 	= set_ioapic_affinity_vector,
 };
 
+static unsigned int startup_msi_vector(unsigned int vector)
+{
+    dprintk(XENLOG_INFO, "startup msi vector %x\n", vector);
+    return 0;
+}
+
+static void ack_msi_vector(unsigned int vector)
+{
+}
+
+static void end_msi_vector(unsigned int vector)
+{
+    ack_APIC_irq();
+}
+
+static void do_nothing(unsigned int vector)
+{
+}
+
+struct hw_interrupt_type msi_irq_type = {
+    .typename   = "msi-irq",
+    .startup    = startup_msi_vector,
+    .shutdown   = do_nothing,
+    .enable     = do_nothing,
+    .disable    = do_nothing,
+    .ack        = ack_msi_vector,
+    .end        = end_msi_vector,
+};
+
+/*
+ * just static value now!
+ */
+int msi_format_setup(struct physdev_msi_format *msi_format)
+{
+    if ( msi_format->vector > NR_IRQS )
+    {
+        gdprintk(XENLOG_G_ERR,
+                 "msi_format_setup vector %x\n", msi_format->vector);
+        return -EINVAL;
+    }
+    msi_format->delivery_mode = INT_DELIVERY_MODE;
+    msi_format->dest_mode = INT_DEST_MODE;
+    msi_format->dest_cpu = cpu_mask_to_apicid(TARGET_CPUS);
+    msi_format->rh = 0;
+    if ( INT_DELIVERY_MODE == dest_LowestPrio )
+        msi_format->rh = 1;
+    return 0;
+}
+
 static inline void init_IO_APIC_traps(void)
 {
     int irq;
diff -r 5c379dcac105 xen/arch/x86/irq.c
--- a/xen/arch/x86/irq.c	Wed Mar 26 00:51:42 2008 +0800
+++ b/xen/arch/x86/irq.c	Wed Mar 26 01:01:08 2008 +0800
@@ -404,7 +404,8 @@ int pirq_acktype(struct domain *d, int i
      * Level-triggered IO-APIC interrupts need to be acknowledged on the CPU
      * on which they were received. This is because we tickle the LAPIC to EOI.
      */
-    if ( !strcmp(desc->handler->typename, "IO-APIC-level") )
+    if ( !strcmp(desc->handler->typename, "IO-APIC-level") ||
+         !strcmp(desc->handler->typename, "msi-irq") )
         return ioapic_ack_new ? ACKTYPE_EOI : ACKTYPE_UNMASK;
 
     /* Legacy PIC interrupts can be acknowledged from any CPU. */
diff -r 5c379dcac105 xen/arch/x86/physdev.c
--- a/xen/arch/x86/physdev.c	Wed Mar 26 00:51:42 2008 +0800
+++ b/xen/arch/x86/physdev.c	Wed Mar 26 01:03:26 2008 +0800
@@ -25,6 +25,11 @@ ioapic_guest_write(
 ioapic_guest_write(
     unsigned long physbase, unsigned int reg, u32 pval);
 
+
+extern struct hw_interrupt_type msi_irq_type;
+
+extern int msi_format_setup(struct physdev_msi_format *msi_format);
+
 static int get_free_pirq(struct domain *d, int type, int index)
 {
     int i;
@@ -95,6 +100,21 @@ static int map_domain_irq(struct domain 
         goto done;
     }
 
+    if ( MAP_IRQ_TYPE_MSI == type )
+    {
+        irq_desc_t         *desc;
+        unsigned long flags;
+
+        desc = &irq_desc[vector];
+
+        spin_lock_irqsave(&desc->lock, flags);
+        if ( desc->handler != &no_irq_type )
+            gdprintk(XENLOG_G_ERR, "Map vector %x to msi while it is in use\n",
+                     vector);
+        desc->handler = &msi_irq_type;
+        spin_unlock_irqrestore(&desc->lock, flags);
+    }
+
     d->arch.pirq_vector[pirq] = vector;
     d->arch.vector_pirq[vector] = pirq;
 
@@ -127,7 +147,23 @@ static int unmap_domain_irq(struct domai
         ret = -EINVAL;
     }
     else
+    {
+        unsigned long flags;
+        irq_desc_t         *desc;
+
+        desc = &irq_desc[vector];
+        spin_lock_irqsave(&desc->lock, flags);
+        if ( desc->handler == &msi_irq_type )
+        {
+            /* MSI is not shared, so should be released already */
+            BUG_ON(desc->status & IRQ_GUEST);
+            irq_desc[vector].handler = &no_irq_type;
+        }
+        spin_unlock_irqrestore(&desc->lock, flags);
+
         d->arch.pirq_vector[pirq] = d->arch.vector_pirq[vector] = 0;
+    }
+
     ret = irq_deny_access(d, pirq);
 
     if ( ret )
@@ -387,7 +423,7 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_H
 
         irq = irq_op.irq;
         ret = -EINVAL;
-        if ( (irq < 0) || (irq >= NR_IRQS) )
+        if ( ((irq < 0) && (irq != AUTO_ASSIGN)) || (irq >= NR_IRQS) )
             break;
 
         irq_op.vector = assign_irq_vector(irq);
@@ -406,6 +442,22 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_H
         break;
     }
 
+    case PHYSDEVOP_msi_format:
+    {
+        struct physdev_msi_format msi_format;
+
+        ret = -EFAULT;
+
+        if ( copy_from_guest(&msi_format, arg, 1) != 0 )
+            break;
+
+        ret = msi_format_setup(&msi_format);
+
+        if ( copy_to_guest(arg, &msi_format, 1) != 0 )
+            ret = -EFAULT;
+        break;
+    }
+
     case PHYSDEVOP_set_iopl: {
         struct physdev_set_iopl set_iopl;
         ret = -EFAULT;
diff -r 5c379dcac105 xen/include/public/physdev.h
--- a/xen/include/public/physdev.h	Wed Mar 26 00:51:42 2008 +0800
+++ b/xen/include/public/physdev.h	Wed Mar 26 00:52:22 2008 +0800
@@ -149,6 +149,20 @@ typedef struct physdev_unmap_irq physdev
 typedef struct physdev_unmap_irq physdev_unmap_irq_t;
 DEFINE_XEN_GUEST_HANDLE(physdev_unmap_irq_t);
 
+#define PHYSDEVOP_msi_format            15
+struct physdev_msi_format
+{
+    /* IN */
+    uint32_t vector;
+    /* OUT */
+    uint32_t delivery_mode;
+    uint32_t dest_mode;
+    uint32_t dest_cpu;
+    uint32_t rh;
+};
+typedef struct physdev_msi_format physdev_msi_format_t;
+DEFINE_XEN_GUEST_HANDLE(physdev_msi_format_t);
+
 /*
  * Argument to physdev_op_compat() hypercall. Superceded by new physdev_op()
  * hypercall since 0x00030202.