[Qemu-devel] [PATCH] virtio: Remove unneeded memcpy

[Qemu-devel] [PATCH] virtio: Remove unneeded memcpy

[Stefan Weil]

Report from valgrind:

==19521== Source and destination overlap in memcpy(0x31d38938, 0x31d38938, 64)
==19521==    at 0x4A0A343: memcpy@@GLIBC_2.14 (in
/usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==19521==    by 0x42774E: virtio_blk_device_init (virtio-blk.c:686)
==19521==    by 0x46EE9E: virtio_device_init (virtio.c:1158)
==19521==    by 0x25405E: device_realize (qdev.c:178)
==19521==    by 0x2559B5: device_set_realized (qdev.c:699)
==19521==    by 0x3A819B: property_set_bool (object.c:1315)
==19521==    by 0x3A6CE0: object_property_set (object.c:803)

Valgrind is right: blk == &s->blks, so it is a memcpy of 64 byte with
source == destination which can be removed.

Reported-by: Dave Airlie <airlied@gmail.com>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
---
 hw/block/virtio-blk.c |    1 -
 1 file changed, 1 deletion(-)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 49a23c3..13f6d82 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -703,7 +703,6 @@ static int virtio_blk_device_init(VirtIODevice *vdev)
 
     s->bs = blk->conf.bs;
     s->conf = &blk->conf;
-    memcpy(&(s->blk), blk, sizeof(struct VirtIOBlkConf));
     s->rq = NULL;
     s->sector_mask = (s->conf->logical_block_size / BDRV_SECTOR_SIZE) - 1;
 
-- 
1.7.9.5

Re: [Qemu-devel] [PATCH] virtio: Remove unneeded memcpy

[Peter Maydell]

On 17 October 2013 20:23, Stefan Weil <sw@weilnetz.de> wrote:
> Report from valgrind:
>
> ==19521== Source and destination overlap in memcpy(0x31d38938, 0x31d38938, 64)
> ==19521==    at 0x4A0A343: memcpy@@GLIBC_2.14 (in
> /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==19521==    by 0x42774E: virtio_blk_device_init (virtio-blk.c:686)
> ==19521==    by 0x46EE9E: virtio_device_init (virtio.c:1158)
> ==19521==    by 0x25405E: device_realize (qdev.c:178)
> ==19521==    by 0x2559B5: device_set_realized (qdev.c:699)
> ==19521==    by 0x3A819B: property_set_bool (object.c:1315)
> ==19521==    by 0x3A6CE0: object_property_set (object.c:803)
>
> Valgrind is right: blk == &s->blks, so it is a memcpy of 64 byte with
> source == destination which can be removed.
>
> Reported-by: Dave Airlie <airlied@gmail.com>
> Signed-off-by: Stefan Weil <sw@weilnetz.de>

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

I did a quick eyeball of the other memcpy()s in hw/*/*virtio*
and I think this is the only one with this problem.

-- PMM

Re: [Qemu-devel] [PATCH] virtio: Remove unneeded memcpy

[Stefan Hajnoczi]

On Thu, Oct 17, 2013 at 09:23:26PM +0200, Stefan Weil wrote:
> Report from valgrind:
> 
> ==19521== Source and destination overlap in memcpy(0x31d38938, 0x31d38938, 64)
> ==19521==    at 0x4A0A343: memcpy@@GLIBC_2.14 (in
> /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==19521==    by 0x42774E: virtio_blk_device_init (virtio-blk.c:686)
> ==19521==    by 0x46EE9E: virtio_device_init (virtio.c:1158)
> ==19521==    by 0x25405E: device_realize (qdev.c:178)
> ==19521==    by 0x2559B5: device_set_realized (qdev.c:699)
> ==19521==    by 0x3A819B: property_set_bool (object.c:1315)
> ==19521==    by 0x3A6CE0: object_property_set (object.c:803)
> 
> Valgrind is right: blk == &s->blks, so it is a memcpy of 64 byte with
> source == destination which can be removed.
> 
> Reported-by: Dave Airlie <airlied@gmail.com>
> Signed-off-by: Stefan Weil <sw@weilnetz.de>
> ---
>  hw/block/virtio-blk.c |    1 -
>  1 file changed, 1 deletion(-)

Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan