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virtio_balloon: transitional interface

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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>
This commit is contained in:
Michael S. Tsirkin 2015-04-15 10:17:43 +09:30 committed by Rusty Russell
parent 9e1a27ea42
commit df81b29c7b
2 changed files with 43 additions and 10 deletions
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21
drivers/virtio/virtio_balloon.c
View File

@ -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);

32
include/uapi/linux/virtio_balloon.h
View File

@ -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 */