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[Qemu-devel] [PULL v5 18/22] vhost: skip ROM sections

From: Michael S. Tsirkin
Subject: [Qemu-devel] [PULL v5 18/22] vhost: skip ROM sections
Date: Tue, 31 Jan 2017 22:19:58 +0200

vhost does not support RO protections on memory at the moment - adding
ROMs would mean that e.g. a buggy guest might change them in-memory - a
condition from which guest reset does not recover. Not nice.

We also definitely don't want to try logging writes into ROMs -
in particular guests set very high addresses for ROM BARs
so logging these writes would waste a lot of memory.

Maybe ROMs could be supported with the iotlb variant -
not sure, but there seems to be no good reason for virtio
to try to do DMA from ROM. So let's just skip ROM memory.

Suggested-by: Laurent Vivier <address@hidden>
Signed-off-by: Michael S. Tsirkin <address@hidden>
Reviewed-by: Laurent Vivier <address@hidden>
Tested-by: Laurent Vivier <address@hidden>
 hw/virtio/vhost.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index b124d97..febe519 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -612,7 +612,8 @@ static void vhost_set_memory(MemoryListener *listener,
 static bool vhost_section(MemoryRegionSection *section)
-    return memory_region_is_ram(section->mr);
+    return memory_region_is_ram(section->mr) &&
+        !memory_region_is_rom(section->mr);
 static void vhost_begin(MemoryListener *listener)

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