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block: pass size to bdrv_unregister_buf()

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The only implementor of bdrv_register_buf() is block/nvme.c, where the
size is not needed when unregistering a buffer. This is because
util/vfio-helpers.c can look up mappings by address.

Future block drivers that implement bdrv_register_buf() may not be able
to do their job given only the buffer address. Add a size argument to
bdrv_unregister_buf().

Also document the assumptions about
bdrv_register_buf()/bdrv_unregister_buf() calls. The same <host, size>
values that were given to bdrv_register_buf() must be given to
bdrv_unregister_buf().

gcc 11.2.1 emits a spurious warning that img_bench()'s buf_size local
variable might be uninitialized, so it's necessary to silence the
compiler.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20221013185908.1297568-5-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi
2022-10-13 14:58:59 -04:00
parent 1f0fea38f4
commit 4f384011c5
7 changed files with 14 additions and 11 deletions
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5
include/block/block-global-state.h
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@@ -243,9 +243,12 @@ void bdrv_del_child(BlockDriverState *parent, BdrvChild *child, Error **errp);
* Register/unregister a buffer for I/O. For example, VFIO drivers are
* interested to know the memory areas that would later be used for I/O, so
* that they can prepare IOMMU mapping etc., to get better performance.
*
* Buffers must not overlap and they must be unregistered with the same <host,
* size> values that they were registered with.
*/
void bdrv_register_buf(BlockDriverState *bs, void *host, size_t size);
void bdrv_unregister_buf(BlockDriverState *bs, void *host);
void bdrv_unregister_buf(BlockDriverState *bs, void *host, size_t size);
void bdrv_cancel_in_flight(BlockDriverState *bs);