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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>
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@ -214,8 +214,8 @@ static inline void update_stat(struct virtio_balloon *vb, int idx,
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u16 tag, u64 val)
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{
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BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
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vb->stats[idx].tag = tag;
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vb->stats[idx].val = val;
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vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
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vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
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}
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#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
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@ -283,18 +283,27 @@ static void virtballoon_changed(struct virtio_device *vdev)
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static inline s64 towards_target(struct virtio_balloon *vb)
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{
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__le32 v;
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s64 target;
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u32 num_pages;
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virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages, &v);
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virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
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&num_pages);
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target = le32_to_cpu(v);
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/* Legacy balloon config space is LE, unlike all other devices. */
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if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
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num_pages = le32_to_cpu((__force __le32)num_pages);
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target = num_pages;
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return target - vb->num_pages;
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}
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static void update_balloon_size(struct virtio_balloon *vb)
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{
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__le32 actual = cpu_to_le32(vb->num_pages);
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u32 actual = vb->num_pages;
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/* Legacy balloon config space is LE, unlike all other devices. */
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if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
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actual = (__force u32)cpu_to_le32(actual);
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virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
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&actual);
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@ -25,6 +25,7 @@
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE. */
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#include <linux/types.h>
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#include <linux/virtio_ids.h>
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#include <linux/virtio_config.h>
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@ -38,9 +39,9 @@
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struct virtio_balloon_config {
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/* Number of pages host wants Guest to give up. */
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__le32 num_pages;
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__u32 num_pages;
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/* Number of pages we've actually got in balloon. */
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__le32 actual;
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__u32 actual;
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};
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#define VIRTIO_BALLOON_S_SWAP_IN 0 /* Amount of memory swapped in */
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@ -51,9 +52,32 @@ struct virtio_balloon_config {
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#define VIRTIO_BALLOON_S_MEMTOT 5 /* Total amount of memory */
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#define VIRTIO_BALLOON_S_NR 6
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/*
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* Memory statistics structure.
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* Driver fills an array of these structures and passes to device.
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*
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* NOTE: fields are laid out in a way that would make compiler add padding
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* between and after fields, so we have to use compiler-specific attributes to
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* pack it, to disable this padding. This also often causes compiler to
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* generate suboptimal code.
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*
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* We maintain this statistics structure format for backwards compatibility,
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* but don't follow this example.
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*
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* If implementing a similar structure, do something like the below instead:
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* struct virtio_balloon_stat {
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* __virtio16 tag;
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* __u8 reserved[6];
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* __virtio64 val;
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* };
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*
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* In other words, add explicit reserved fields to align field and
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* structure boundaries at field size, avoiding compiler padding
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* without the packed attribute.
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*/
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struct virtio_balloon_stat {
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__u16 tag;
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__u64 val;
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__virtio16 tag;
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__virtio64 val;
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} __attribute__((packed));
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#endif /* _LINUX_VIRTIO_BALLOON_H */
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