[Qemu-devel] [PULL 21/31] xen-hvm: ignore background I/O sections

[Paolo Bonzini]

From: Paul Durrant <address@hidden>

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 <address@hidden>
Cc: Stefano Stabellini <address@hidden>
Cc: Anthony Perard <address@hidden>
Cc: Paolo Bonzini <address@hidden>
Message-Id: <address@hidden>
Acked-by: Anthony PERARD <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
 xen-hvm.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/xen-hvm.c b/xen-hvm.c
index c14e778..01ee25d 100644
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -511,8 +511,13 @@ 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);
 }
@@ -521,10 +526,15 @@ 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,
-- 
2.5.5