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Subject[PATCH v3 1/6] 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>
---
include/uapi/linux/virtio_balloon.h | 11 ++++++++--
drivers/virtio/virtio_balloon.c | 43 +++++++++++++++++++++++++++++--------
2 files changed, 43 insertions(+), 11 deletions(-)

diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
index 4b0488f..f81b220 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 */
@@ -56,4 +57,10 @@ struct virtio_balloon_stat {
__u64 val;
} __attribute__((packed));

+struct virtio_balloon_stat_modern {
+ __le16 tag;
+ __u8 reserved[6];
+ __le64 val;
+};
+
#endif /* _LINUX_VIRTIO_BALLOON_H */
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 6a356e3..0583720 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -77,7 +77,10 @@ struct virtio_balloon {

/* Memory statistics */
int need_stats_update;
- struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
+ union {
+ struct virtio_balloon_stat_modern stats[VIRTIO_BALLOON_S_NR];
+ struct virtio_balloon_stat legacy_stats[VIRTIO_BALLOON_S_NR];
+ };

/* To register callback in oom notifier call chain */
struct notifier_block nb;
@@ -88,6 +91,14 @@ static struct virtio_device_id id_table[] = {
{ 0 },
};

+static void stats_sg_init(struct virtio_balloon *vb, struct scatterlist *sg)
+{
+ if (virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
+ sg_init_one(sg, vb->stats, sizeof(vb->stats));
+ else
+ sg_init_one(sg, vb->legacy_stats, sizeof(vb->legacy_stats));
+}
+
static u32 page_to_balloon_pfn(struct page *page)
{
unsigned long pfn = page_to_pfn(page);
@@ -214,8 +225,13 @@ 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;
+ if (virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1)) {
+ vb->stats[idx].tag = cpu_to_le32(tag);
+ vb->stats[idx].val = cpu_to_le64(val);
+ } else {
+ vb->legacy_stats[idx].tag = tag;
+ vb->legacy_stats[idx].val = val;
+ }
}

#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
@@ -269,7 +285,7 @@ static void stats_handle_request(struct virtio_balloon *vb)
vq = vb->stats_vq;
if (!virtqueue_get_buf(vq, &len))
return;
- sg_init_one(&sg, vb->stats, sizeof(vb->stats));
+ stats_sg_init(vb, &sg);
virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
virtqueue_kick(vq);
}
@@ -283,18 +299,27 @@ 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,
+ &num_pages);

- virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages, &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 = le32_to_cpu(v);
+ 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);
@@ -397,7 +422,7 @@ static int init_vqs(struct virtio_balloon *vb)
* Prime this virtqueue with one buffer so the hypervisor can
* use it to signal us later (it can't be broken yet!).
*/
- sg_init_one(&sg, vb->stats, sizeof vb->stats);
+ stats_sg_init(vb, &sg);
if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
< 0)
BUG();
--
MST


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