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Commit df81b29c authored by Michael S. Tsirkin's avatar Michael S. Tsirkin Committed by Rusty Russell
Browse files

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: default avatarMichael S. Tsirkin <mst@redhat.com>
Acked-by: default avatarCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 9e1a27ea

drivers/virtio/virtio_balloon.c

+15 −6
Original line number Diff line number Diff line
@@ -214,8 +214,8 @@ static inline void update_stat(struct virtio_balloon *vb, int idx, 
			       u16 tag, u64 val)

{

	BUG_ON(idx >= VIRTIO_BALLOON_S_NR);

	vb->stats[idx].tag = tag;

	vb->stats[idx].val = val;

	vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);

	vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);

}



#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
@@ -283,18 +283,27 @@ static void virtballoon_changed(struct virtio_device *vdev) 


static inline s64 towards_target(struct virtio_balloon *vb)

{

	__le32 v;

	s64 target;

	u32 num_pages;



	virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages, &v);

	virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,

		     &num_pages);



	target = le32_to_cpu(v);

	/* Legacy balloon config space is LE, unlike all other devices. */

	if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))

		num_pages = le32_to_cpu((__force __le32)num_pages);



	target = num_pages;

	return target - vb->num_pages;

}



static void update_balloon_size(struct virtio_balloon *vb)

{

	__le32 actual = cpu_to_le32(vb->num_pages);

	u32 actual = vb->num_pages;



	/* Legacy balloon config space is LE, unlike all other devices. */

	if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))

		actual = (__force u32)cpu_to_le32(actual);



	virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,

		      &actual);

include/uapi/linux/virtio_balloon.h

+28 −4
Original line number Diff line number Diff line
@@ -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 */