diff options
| author | Michael S. Tsirkin <mst@redhat.com> | 2015-04-15 02:47:43 +0200 |
|---|---|---|
| committer | Rusty Russell <rusty@rustcorp.com.au> | 2015-04-15 05:11:09 +0200 |
| commit | df81b29c7b81b9d70ee29b7a263dd5009daa0ce4 (patch) | |
| tree | a73a9ac6aa72aa32bd7e25a25148044025caa31f /include/uapi | |
| parent | virtio_ring: Update weak barriers to use dma_wmb/rmb (diff) | |
| download | linux-df81b29c7b81b9d70ee29b7a263dd5009daa0ce4.tar.xz linux-df81b29c7b81b9d70ee29b7a263dd5009daa0ce4.zip | |
virtio_balloon: transitional interface
Virtio 1.0 doesn't include a modern balloon device.
But it's not a big change to support a transitional
balloon device: this has the advantage of supporting
existing drivers, transparently.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'include/uapi')
| -rw-r--r-- | include/uapi/linux/virtio_balloon.h | 32 |
1 files changed, 28 insertions, 4 deletions
diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h index 4b0488f20b2e..984169a819ee 100644 --- a/include/uapi/linux/virtio_balloon.h +++ b/include/uapi/linux/virtio_balloon.h @@ -25,6 +25,7 @@ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ +#include <linux/types.h> #include <linux/virtio_ids.h> #include <linux/virtio_config.h> @@ -38,9 +39,9 @@ struct virtio_balloon_config { /* Number of pages host wants Guest to give up. */ - __le32 num_pages; + __u32 num_pages; /* Number of pages we've actually got in balloon. */ - __le32 actual; + __u32 actual; }; #define VIRTIO_BALLOON_S_SWAP_IN 0 /* Amount of memory swapped in */ @@ -51,9 +52,32 @@ struct virtio_balloon_config { #define VIRTIO_BALLOON_S_MEMTOT 5 /* Total amount of memory */ #define VIRTIO_BALLOON_S_NR 6 +/* + * Memory statistics structure. + * Driver fills an array of these structures and passes to device. + * + * NOTE: fields are laid out in a way that would make compiler add padding + * between and after fields, so we have to use compiler-specific attributes to + * pack it, to disable this padding. This also often causes compiler to + * generate suboptimal code. + * + * We maintain this statistics structure format for backwards compatibility, + * but don't follow this example. + * + * If implementing a similar structure, do something like the below instead: + * struct virtio_balloon_stat { + * __virtio16 tag; + * __u8 reserved[6]; + * __virtio64 val; + * }; + * + * In other words, add explicit reserved fields to align field and + * structure boundaries at field size, avoiding compiler padding + * without the packed attribute. + */ struct virtio_balloon_stat { - __u16 tag; - __u64 val; + __virtio16 tag; + __virtio64 val; } __attribute__((packed)); #endif /* _LINUX_VIRTIO_BALLOON_H */ |