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@xxxxxxxxxx>
---
include/uapi/linux/virtio_balloon.h | 11 +++++++++--
drivers/virtio/virtio_balloon.c | 29 +++++++++++++++++++++--------
2 files changed, 30 insertions(+), 10 deletions(-)
diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
index 4b0488f..71ef93b 100644
--- a/include/uapi/linux/virtio_balloon.h
+++ b/include/uapi/linux/virtio_balloon.h
@@ -38,9 +38,9 @@
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 +51,16 @@ struct virtio_balloon_config {
#define VIRTIO_BALLOON_S_MEMTOT 5 /* Total amount of memory */
#define VIRTIO_BALLOON_S_NR 6
+/* Legacy stat structure. We keep it around to avoid breaking old userspace. */
struct virtio_balloon_stat {
__u16 tag;
__u64 val;
} __attribute__((packed));
+struct virtio_balloon_stat_modern {
+ __u8 reserved[6];
+ __virtio16 tag;
+ __virtio64 val;
+};
+
#endif /* _LINUX_VIRTIO_BALLOON_H */
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 6a356e3..574267f 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -77,7 +77,7 @@ struct virtio_balloon {
/* Memory statistics */
int need_stats_update;
- struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
+ struct virtio_balloon_stat_modern stats[VIRTIO_BALLOON_S_NR];
/* To register callback in oom notifier call chain */
struct notifier_block nb;
@@ -269,7 +269,11 @@ 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));
+ if (virtio_has_feature(vdev, VIRTIO_F_VERSION_1))
+ sg_init_one(&sg, vb->stats, sizeof(vb->stats));
+ else
+ sg_init_one(&sg, &vb->stats->tag, sizeof(vb->stats) -
+ offsetof(typeof(*vb->stats, tag);
virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
virtqueue_kick(vq);
}
@@ -283,21 +287,30 @@ 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(num_pages);
- virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
- &actual);
+ virtio_cwrite(vb->vdev, struct virtio_balloon_config,
+ actual, &actual);
}
/*
--
MST
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