diff -r ec6d1ed854fb xen/arch/x86/hvm/vlapic.c
--- a/xen/arch/x86/hvm/vlapic.c	Thu Jul 03 10:47:27 2008 +0800
+++ b/xen/arch/x86/hvm/vlapic.c	Thu Jul 03 11:26:54 2008 +0800
@@ -413,9 +413,8 @@
 
     if ( vlapic_test_and_clear_vector(vector, &vlapic->regs->data[APIC_TMR]) )
         vioapic_update_EOI(vlapic_domain(vlapic), vector);
-	
-    if ( iommu_enabled )
-        hvm_dpci_msi_eoi(current->domain, vector);
+
+    hvm_dpci_msi_eoi(current->domain, vector);
 }
 
 static int vlapic_ipi(
diff -r ec6d1ed854fb xen/arch/x86/irq.c
--- a/xen/arch/x86/irq.c	Thu Jul 03 10:47:27 2008 +0800
+++ b/xen/arch/x86/irq.c	Thu Jul 03 11:26:54 2008 +0800
@@ -48,6 +48,20 @@
     end_none
 };
 
+static void irq_timer_fn(void *data)
+{
+    irq_desc_t *desc = data;
+    unsigned vector = desc - irq_desc;
+    unsigned long flags;
+
+    spin_lock_irqsave(&desc->lock, flags);
+
+    desc->status &= ~IRQ_INPROGRESS;
+    desc->handler->enable(vector);
+
+    spin_unlock_irqrestore(&desc->lock, flags);
+}
+
 atomic_t irq_err_count;
 
 asmlinkage void do_IRQ(struct cpu_user_regs *regs)
@@ -59,6 +73,21 @@
     perfc_incr(irqs);
 
     spin_lock(&desc->lock);
+
+    if ( unlikely(desc->status & IRQ_INPROGRESS) )
+    {
+        desc->handler->disable(vector);
+        desc->handler->ack(vector);
+        if ( !desc->timer )
+        {
+            desc->timer = xmalloc(struct timer);
+            init_timer(desc->timer, irq_timer_fn, desc, smp_processor_id());
+        }
+        set_timer(desc->timer, NOW() + MILLISECS(1));
+        spin_unlock(&desc->lock);
+        return;
+    }
+
     desc->handler->ack(vector);
 
     if ( likely(desc->status & IRQ_GUEST) )
@@ -206,8 +235,11 @@
     irq_desc_t         *desc = &irq_desc[vector];
     irq_guest_action_t *action = (irq_guest_action_t *)desc->action;
     struct domain      *d;
-    int                 i, sp;
+    int                 i, sp, is_hvm_edge_irq = 0;
     struct pending_eoi *peoi = this_cpu(pending_eoi);
+
+    if ( action->ack_type == ACKTYPE_NONE )
+        desc->status |= IRQ_INPROGRESS;
 
     if ( unlikely(action->nr_guests == 0) )
     {
@@ -239,8 +271,12 @@
             action->in_flight++;
         if (!hvm_do_IRQ_dpci(d, irq))
             send_guest_pirq(d, irq);
+        else
+            is_hvm_edge_irq = action->ack_type == ACKTYPE_NONE;
+    }
 
-    }
+    if ( !is_hvm_edge_irq )
+        desc->status &= ~IRQ_INPROGRESS;
 }
 
 /* Flush all ready EOIs from the top of this CPU's pending-EOI stack. */
diff -r ec6d1ed854fb xen/drivers/passthrough/io.c
--- a/xen/drivers/passthrough/io.c	Thu Jul 03 10:47:27 2008 +0800
+++ b/xen/drivers/passthrough/io.c	Thu Jul 03 11:26:54 2008 +0800
@@ -220,15 +220,26 @@
 {
     struct hvm_irq_dpci *hvm_irq_dpci = d->arch.hvm_domain.irq.dpci;
     int pirq;
+    unsigned long flags;
+    irq_desc_t *desc;
 
     if ( !iommu_enabled || (hvm_irq_dpci == NULL) )
        return;
 
     pirq = hvm_irq_dpci->msi_gvec_pirq[vector];
+
     if ( ( pirq >= 0 ) && (pirq < NR_PIRQS) &&
          (hvm_irq_dpci->mirq[pirq].flags & HVM_IRQ_DPCI_VALID) &&
          (hvm_irq_dpci->mirq[pirq].flags & HVM_IRQ_DPCI_MSI) )
-         pirq_guest_eoi(d, pirq);
+    {
+        int vec;
+        vec = domain_irq_to_vector(d, pirq);
+        desc = &irq_desc[vec];
+
+        spin_lock_irqsave(&desc->lock, flags);
+        desc->status &= ~IRQ_INPROGRESS;
+        spin_unlock_irqrestore(&desc->lock, flags);
+    }
 }
 
 void hvm_dpci_eoi(struct domain *d, unsigned int guest_gsi,
diff -r ec6d1ed854fb xen/include/xen/irq.h
--- a/xen/include/xen/irq.h	Thu Jul 03 10:47:27 2008 +0800
+++ b/xen/include/xen/irq.h	Thu Jul 03 11:26:54 2008 +0800
@@ -56,6 +56,7 @@
     unsigned int status;		/* IRQ status */
     hw_irq_controller *handler;
     struct msi_desc   *msi_desc;
+    struct timer      *timer;
     struct irqaction *action;	/* IRQ action list */
     unsigned int depth;		/* nested irq disables */
     spinlock_t lock;