xen: support pirq_eoi_map

The pirq_eoi_map is a bitmap offered by Xen to check which pirqs need to
be EOI'd without having to issue an hypercall every time.
We use PHYSDEVOP_pirq_eoi_gmfn_v2 to map the bitmap, then if we
succeed we use pirq_eoi_map to check whether pirqs need eoi.

Changes in v3:

- explicitly use PHYSDEVOP_pirq_eoi_gmfn_v2 rather than
PHYSDEVOP_pirq_eoi_gmfn;

- introduce pirq_check_eoi_map, a function to check if a pirq needs an
eoi using the map;

-rename pirq_needs_eoi into pirq_needs_eoi_flag;

- introduce a function pointer called pirq_needs_eoi that is going to be
set to the right implementation depending on the availability of
PHYSDEVOP_pirq_eoi_gmfn_v2.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

include/xen/interface/physdev.h

@@ -38,6 +38,27 @@ struct physdev_eoi {
 	uint32_t irq;
 };
 
+/*
+ * Register a shared page for the hypervisor to indicate whether the guest
+ * must issue PHYSDEVOP_eoi. The semantics of PHYSDEVOP_eoi change slightly
+ * once the guest used this function in that the associated event channel
+ * will automatically get unmasked. The page registered is used as a bit
+ * array indexed by Xen's PIRQ value.
+ */
+#define PHYSDEVOP_pirq_eoi_gmfn_v1       17
+/*
+ * Register a shared page for the hypervisor to indicate whether the
+ * guest must issue PHYSDEVOP_eoi. This hypercall is very similar to
+ * PHYSDEVOP_pirq_eoi_gmfn_v1 but it doesn't change the semantics of
+ * PHYSDEVOP_eoi. The page registered is used as a bit array indexed by
+ * Xen's PIRQ value.
+ */
+#define PHYSDEVOP_pirq_eoi_gmfn_v2       28
+struct physdev_pirq_eoi_gmfn {
+    /* IN */
+    unsigned long gmfn;
+};
+
 /*
  * Query the status of an IRQ line.
  * @arg == pointer to physdev_irq_status_query structure.