[PATCH v3] xen-hvm: ignore background I/O sections

* [PATCH v3] xen-hvm: ignore background I/O sections
@ 2016-05-09 16:31 Paul Durrant
  2016-05-25 15:52 ` [Qemu-devel] " Anthony PERARD
  2016-05-25 15:52 ` Anthony PERARD
  0 siblings, 2 replies; 7+ messages in thread
From: Paul Durrant @ 2016-05-09 16:31 UTC (permalink / raw)
  To: qemu-devel, xen-devel
  Cc: Anthony Perard, Paolo Bonzini, Paul Durrant, Stefano Stabellini

Since Xen will correctly handle accesses to unimplemented I/O ports (by
returning all 1's for reads and ignoring writes) there is no need for
QEMU to register backgroud I/O sections.

This patch therefore adds checks to xen_io_add/del so that sections with
memory-region ops pointing at 'unassigned_io_ops' are ignored.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
---

v3:
 - Really add missing braces.

v2:
 - Add missing braces
---
 xen-hvm.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/xen-hvm.c b/xen-hvm.c
index 039680a..e394407 100644
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -510,8 +510,13 @@ static void xen_io_add(MemoryListener *listener,
                        MemoryRegionSection *section)
 {
     XenIOState *state = container_of(listener, XenIOState, io_listener);
+    MemoryRegion *mr = section->mr;
 
-    memory_region_ref(section->mr);
+    if (mr->ops == &unassigned_io_ops) {
+        return;
+    }
+
+    memory_region_ref(mr);
 
     xen_map_io_section(xen_xc, xen_domid, state->ioservid, section);
 }
@@ -520,10 +525,15 @@ static void xen_io_del(MemoryListener *listener,
                        MemoryRegionSection *section)
 {
     XenIOState *state = container_of(listener, XenIOState, io_listener);
+    MemoryRegion *mr = section->mr;
+
+    if (mr->ops == &unassigned_io_ops) {
+        return;
+    }
 
     xen_unmap_io_section(xen_xc, xen_domid, state->ioservid, section);
 
-    memory_region_unref(section->mr);
+    memory_region_unref(mr);
 }
 
 static void xen_device_realize(DeviceListener *listener,
-- 
2.1.4


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel

^ permalink raw reply related	[flat|nested] 7+ messages in thread