xen/irq: Add support to check if IRQ line is shared with other domains.

We do this via the PHYSDEVOP_irq_status_query support hypervisor call.
We will get a positive value if another domain has binded its
PIRQ to the specified GSI (IRQ line).

[v2: Deal with v2.6.37-rc1 rebase fallout]
[v3: Deal with stable/irq.cleanup fallout]
[v4: xen_ignore_irq->xen_test_irq_shared]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

2 files changed, 15 insertions, 0 deletions

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index ac0e22826357..0ac7a149e7f2 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -1508,6 +1508,18 @@ void xen_poll_irq(int irq)
         xen_poll_irq_timeout(irq, 0 /* no timeout */);
 }
 
+/* Check whether the IRQ line is shared with other guests. */
+int xen_test_irq_shared(int irq)
+{
+        struct irq_info *info = info_for_irq(irq);
+        struct physdev_irq_status_query irq_status = { .irq = info->u.pirq.pirq };
+
+        if (HYPERVISOR_physdev_op(PHYSDEVOP_irq_status_query, &irq_status))
+                return 0;
+        return !(irq_status.flags & XENIRQSTAT_shared);
+}
+EXPORT_SYMBOL_GPL(xen_test_irq_shared);
+
 void xen_irq_resume(void)
 {
         unsigned int cpu, evtchn;
diff --git a/include/xen/events.h b/include/xen/events.h
index 9aecc0b5a0e6..932e54051d3e 100644
--- a/include/xen/events.h
+++ b/include/xen/events.h
@@ -95,4 +95,7 @@ int xen_destroy_irq(int irq);
 /* Return irq from pirq */
 int xen_irq_from_pirq(unsigned pirq);
 
+/* Determine whether to ignore this IRQ if it is passed to a guest. */
+int xen_test_irq_shared(int irq);
+
 #endif  /* _XEN_EVENTS_H */