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    Subject[PATCH v28 4/4] virtio-balloon: VIRTIO_BALLOON_F_PAGE_POISON
    Date
    The VIRTIO_BALLOON_F_PAGE_POISON feature bit is used to indicate if the
    guest is using page poisoning. Guest writes to the poison_val config
    field to tell host about the page poisoning value in use.

    Signed-off-by: Wei Wang <wei.w.wang@intel.com>
    Suggested-by: Michael S. Tsirkin <mst@redhat.com>
    Cc: Michael S. Tsirkin <mst@redhat.com>
    Cc: Michal Hocko <mhocko@suse.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    ---
    drivers/virtio/virtio_balloon.c | 13 +++++++++++++
    include/uapi/linux/virtio_balloon.h | 3 +++
    2 files changed, 16 insertions(+)

    diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
    index 39ecce3..9fa7fcf 100644
    --- a/drivers/virtio/virtio_balloon.c
    +++ b/drivers/virtio/virtio_balloon.c
    @@ -685,6 +685,7 @@ static struct file_system_type balloon_fs = {
    static int virtballoon_probe(struct virtio_device *vdev)
    {
    struct virtio_balloon *vb;
    + __u32 poison_val;
    int err;

    if (!vdev->config->get) {
    @@ -728,6 +729,12 @@ static int virtballoon_probe(struct virtio_device *vdev)
    goto out_del_vqs;
    }
    INIT_WORK(&vb->report_free_page_work, report_free_page_func);
    + if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
    + page_poison_val_get((u8 *)&poison_val);
    + memset(&poison_val, poison_val, sizeof(poison_val));
    + virtio_cwrite(vb->vdev, struct virtio_balloon_config,
    + poison_val, &poison_val);
    + }
    }

    vb->nb.notifier_call = virtballoon_oom_notify;
    @@ -846,6 +853,11 @@ static int virtballoon_restore(struct virtio_device *vdev)

    static int virtballoon_validate(struct virtio_device *vdev)
    {
    + uint8_t unused;
    +
    + if (!page_poison_val_get(&unused))
    + __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
    +
    __virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM);
    return 0;
    }
    @@ -855,6 +867,7 @@ static unsigned int features[] = {
    VIRTIO_BALLOON_F_STATS_VQ,
    VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
    VIRTIO_BALLOON_F_FREE_PAGE_HINT,
    + VIRTIO_BALLOON_F_PAGE_POISON,
    };

    static struct virtio_driver virtio_balloon_driver = {
    diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
    index 0c654db..3f97067 100644
    --- a/include/uapi/linux/virtio_balloon.h
    +++ b/include/uapi/linux/virtio_balloon.h
    @@ -35,6 +35,7 @@
    #define VIRTIO_BALLOON_F_STATS_VQ 1 /* Memory Stats virtqueue */
    #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM 2 /* Deflate balloon on OOM */
    #define VIRTIO_BALLOON_F_FREE_PAGE_HINT 3 /* VQ to report free pages */
    +#define VIRTIO_BALLOON_F_PAGE_POISON 4 /* Guest is using page poisoning */

    /* Size of a PFN in the balloon interface. */
    #define VIRTIO_BALLOON_PFN_SHIFT 12
    @@ -47,6 +48,8 @@ struct virtio_balloon_config {
    __u32 actual;
    /* Free page report command id, readonly by guest */
    __u32 free_page_report_cmd_id;
    + /* Stores PAGE_POISON if page poisoning is in use */
    + __u32 poison_val;
    };

    #define VIRTIO_BALLOON_S_SWAP_IN 0 /* Amount of memory swapped in */
    --
    2.7.4
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