[PATCH v2 2/2] linux/xen: support pirq_eoi_map

[Stefano Stabellini <stefano.stabellini@eu.citrix.com>]

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.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
 drivers/xen/events.c            |   17 ++++++++++++++++-
 include/xen/interface/physdev.h |   12 ++++++++++++
 2 files changed, 28 insertions(+), 1 deletions(-)

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 6e075cd..7fdc738 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -37,6 +37,7 @@
 #include <asm/idle.h>
 #include <asm/io_apic.h>
 #include <asm/sync_bitops.h>
+#include <asm/xen/page.h>
 #include <asm/xen/pci.h>
 #include <asm/xen/hypercall.h>
 #include <asm/xen/hypervisor.h>
@@ -108,6 +109,7 @@ struct irq_info {
 #define PIRQ_SHAREABLE	(1 << 1)
 
 static int *evtchn_to_irq;
+static unsigned long *pirq_eoi_map;
 
 static DEFINE_PER_CPU(unsigned long [NR_EVENT_CHANNELS/BITS_PER_LONG],
 		      cpu_evtchn_mask);
@@ -274,6 +276,9 @@ static bool pirq_needs_eoi(unsigned irq)
 
 	BUG_ON(info->type != IRQT_PIRQ);
 
+	if (pirq_eoi_map != NULL)
+		return test_bit(irq, pirq_eoi_map);
+
 	return info->u.pirq.flags & PIRQ_NEEDS_EOI;
 }
 
@@ -1693,7 +1698,7 @@ void xen_callback_vector(void) {}
 
 void __init xen_init_IRQ(void)
 {
-	int i;
+	int i, rc;
 
 	evtchn_to_irq = kcalloc(NR_EVENT_CHANNELS, sizeof(*evtchn_to_irq),
 				    GFP_KERNEL);
@@ -1714,8 +1719,18 @@ void __init xen_init_IRQ(void)
 		 * __acpi_register_gsi can point at the right function */
 		pci_xen_hvm_init();
 	} else {
+		struct physdev_pirq_eoi_gmfn eoi_gmfn;
+
 		irq_ctx_init(smp_processor_id());
 		if (xen_initial_domain())
 			pci_xen_initial_domain();
+
+		pirq_eoi_map = (void *)__get_free_page(GFP_KERNEL|__GFP_ZERO);
+		eoi_gmfn.gmfn = virt_to_mfn(pirq_eoi_map);
+		rc = HYPERVISOR_physdev_op(PHYSDEVOP_pirq_eoi_gmfn, &eoi_gmfn);
+		if (rc != 0) {
+			free_page((unsigned long) pirq_eoi_map);
+			pirq_eoi_map = NULL;
+		}
 	}
 }
diff --git a/include/xen/interface/physdev.h b/include/xen/interface/physdev.h
index c1080d9..132c61f 100644
--- a/include/xen/interface/physdev.h
+++ b/include/xen/interface/physdev.h
@@ -39,6 +39,18 @@ struct physdev_eoi {
 };
 
 /*
+ * Register a shared page for the hypervisor to indicate whether the
+ * guest must issue PHYSDEVOP_eoi. The page registered is used as a bit
+ * array indexed by Xen's PIRQ value.
+ */
+#define PHYSDEVOP_pirq_eoi_gmfn      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.
  */
-- 
1.7.2.5