--- 2006-04-21/linux-2.6-xen-sparse/kernel/irq/handle.c	2006-03-20 06:53:29.000000000 +0100
+++ 2006-04-21/linux-2.6-xen-sparse/kernel/irq/handle.c	2006-04-27 10:16:35.000000000 +0200
@@ -12,6 +12,10 @@
 #include <linux/interrupt.h>
 #include <linux/kernel_stat.h>
 
+#ifdef CONFIG_XEN
+#include <asm/hypervisor.h>
+#endif
+
 #include "internals.h"
 
 /*
@@ -76,10 +80,19 @@ irqreturn_t no_action(int cpl, void *dev
 /*
  * Have got an event to handle:
  */
-fastcall int handle_IRQ_event(unsigned int irq, struct pt_regs *regs,
+fastcall /*irqreturn_t*/int handle_IRQ_event(unsigned int irq, struct pt_regs *regs,
 				struct irqaction *action)
 {
-	int ret, retval = 0, status = 0;
+	irqreturn_t ret, retval = IRQ_NONE;
+	unsigned int status = 0;
+
+#ifdef CONFIG_XEN
+	unsigned int pirq = irq_to_pirq(irq);
+
+	BUILD_BUG_ON(BITS_TO_LONGS(NR_PIRQS) > sizeof(((shared_info_t *)0)->pirq_shared));
+	if (pirq < NR_PIRQS && test_bit(pirq, HYPERVISOR_shared_info->pirq_shared))
+		retval = IRQ_HANDLED;
+#endif
 
 	if (!(action->flags & SA_INTERRUPT))
 		local_irq_enable();
--- 2006-04-21/xen/arch/x86/irq.c.0	2006-04-24 10:56:27.000000000 +0200
+++ 2006-04-21/xen/arch/x86/irq.c	2006-04-27 09:54:43.000000000 +0200
@@ -200,7 +200,7 @@ static void __do_IRQ_guest(int vector)
         if ( (action->ack_type != ACKTYPE_NONE) &&
              !test_and_set_bit(irq, d->pirq_mask) )
             action->in_flight++;
-        send_guest_pirq(d, irq);
+        send_guest_pirq(d, irq, action->nr_guests > 1);
     }
 }
 
--- 2006-04-21/xen/arch/ia64/xen/irq.c.0	2006-04-06 17:50:25.000000000 +0200
+++ 2006-04-21/xen/arch/ia64/xen/irq.c	2006-04-27 09:54:32.000000000 +0200
@@ -411,7 +411,7 @@ static void __do_IRQ_guest(int irq)
         if ( (action->ack_type != ACKTYPE_NONE) &&
              !test_and_set_bit(irq, &d->pirq_mask) )
             action->in_flight++;
-        send_guest_pirq(d, irq);
+        send_guest_pirq(d, irq, action->nr_guests > 1);
     }
 }
 
--- 2006-04-21/xen/common/event_channel.c.0	2006-04-06 17:50:26.000000000 +0200
+++ 2006-04-21/xen/common/event_channel.c	2006-04-27 09:57:36.000000000 +0200
@@ -539,13 +539,20 @@ void send_guest_virq(struct vcpu *v, int
 }
 
 
-void send_guest_pirq(struct domain *d, int pirq)
+void send_guest_pirq(struct domain *d, int pirq, int shared)
 {
     int port = d->pirq_to_evtchn[pirq];
     struct evtchn *chn;
+    shared_info_t *s = d->shared_info;
 
     ASSERT(port != 0);
 
+    BUILD_BUG_ON(BITS_TO_LONGS(NR_PIRQS) > sizeof(((shared_info_t *)0)->pirq_shared));
+    if (shared)
+        set_bit(pirq, s->pirq_shared);
+    else
+        clear_bit(pirq, s->pirq_shared);
+
     chn = evtchn_from_port(d, port);
     evtchn_set_pending(d->vcpu[chn->notify_vcpu_id], port);
 }
--- 2006-04-21/xen/include/public/xen.h.0	2006-04-07 10:05:06.000000000 +0200
+++ 2006-04-21/xen/include/public/xen.h	2006-04-27 11:36:53.000000000 +0200
@@ -408,6 +408,14 @@ typedef struct shared_info {
 
     struct arch_shared_info arch;
 
+    /*
+     * Indicator which PIRQs are shared with other domains, allowing the guest
+     * to not consider respective interrupts spurious even if no handler claims
+     * them, while still being able to detect spurious occurrences of un-shared
+     * interrupts.
+     */
+    unsigned long pirq_shared[256 / (8 * sizeof(unsigned long))];
+
 };
 typedef struct shared_info shared_info_t;
 
--- 2006-04-21/xen/include/xen/event.h.0	2006-04-06 17:50:27.000000000 +0200
+++ 2006-04-21/xen/include/xen/event.h	2006-04-27 09:54:21.000000000 +0200
@@ -35,8 +35,9 @@ extern void send_guest_virq(struct vcpu 
  * send_guest_pirq:
  *  @d:        Domain to which physical IRQ should be sent
  *  @pirq:     Physical IRQ number
+ *  @shared:   Indicator whether IRQ is shared with other domain(s)
  */
-extern void send_guest_pirq(struct domain *d, int pirq);
+extern void send_guest_pirq(struct domain *d, int pirq, int shared);
 
 #define evtchn_pending(d, p)                    \
     (test_bit((p), &(d)->shared_info->evtchn_pending[0]))