In pt_irq_time_out() the following code loops through all used
guest_gsi:

    list_for_each_entry ( digl, &irq_map->digl_list, list )
    {
        guest_gsi = digl->gsi;
        machine_gsi = dpci->girq[guest_gsi].machine_gsi;
	...
    }

And a little later on machine_gsi is used.
That is the last machine_gsi found is used,
rather than all of the machine_gsi that are found.

This seems to be incorrect to me,
but I am unsure of how to test this.

This code appears to have been introduced in
"vt-d: Support intra-domain shared interrupt" by Weidong Han.

Cc: Weidong Han <weidong.han@intel.com>
Cc: Yuji Shimada <shimada-yxb@necst.nec.co.jp>
Signed-off-by: Simon Horman <horms@verge.net.au>

Index: xen-unstable.hg/xen/drivers/passthrough/io.c
===================================================================
--- xen-unstable.hg.orig/xen/drivers/passthrough/io.c	2009-03-09 12:44:48.000000000 +1100
+++ xen-unstable.hg/xen/drivers/passthrough/io.c	2009-03-09 12:58:28.000000000 +1100
@@ -37,6 +37,9 @@ static void pt_irq_time_out(void *data)
     struct hvm_irq_dpci *dpci = NULL;
     struct dev_intx_gsi_link *digl;
     uint32_t device, intx;
+    DECLARE_BITMAP(machine_gsi_map, NR_IRQS);
+
+    bitmap_zero(machine_gsi_map, NR_IRQS);
 
     spin_lock(&irq_map->dom->event_lock);
 
@@ -46,16 +49,31 @@ static void pt_irq_time_out(void *data)
     {
         guest_gsi = digl->gsi;
         machine_gsi = dpci->girq[guest_gsi].machine_gsi;
+        set_bit(machine_gsi, machine_gsi_map);
         device = digl->device;
         intx = digl->intx;
         hvm_pci_intx_deassert(irq_map->dom, device, intx);
     }
 
-    clear_bit(machine_gsi, dpci->dirq_mask);
-    vector = domain_irq_to_vector(irq_map->dom, machine_gsi);
-    dpci->mirq[machine_gsi].pending = 0;
+    for ( machine_gsi = find_first_bit(machine_gsi_map, NR_IRQS);
+          machine_gsi < NR_IRQS;
+          machine_gsi = find_next_bit(machine_gsi_map, NR_IRQS,
+                                      machine_gsi + 1) )
+    {
+        clear_bit(machine_gsi, dpci->dirq_mask);
+        vector = domain_irq_to_vector(irq_map->dom, machine_gsi);
+        dpci->mirq[machine_gsi].pending = 0;
+    }
+
     spin_unlock(&irq_map->dom->event_lock);
-    pirq_guest_eoi(irq_map->dom, machine_gsi);
+
+    for ( machine_gsi = find_first_bit(machine_gsi_map, NR_IRQS);
+          machine_gsi < NR_IRQS;
+          machine_gsi = find_next_bit(machine_gsi_map, NR_IRQS,
+                                      machine_gsi + 1) )
+    {
+        pirq_guest_eoi(irq_map->dom, machine_gsi);
+    }
 }
 
 int pt_irq_create_bind_vtd(

-- 

-- 
Simon Horman
  VA Linux Systems Japan K.K., Sydney, Australia Satellite Office
  H: www.vergenet.net/~horms/             W: www.valinux.co.jp/en