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SubjectRe: [PATCH v28 4/4] virtio-balloon: VIRTIO_BALLOON_F_PAGE_POISON
On Thu, Feb 08, 2018 at 05:50:20PM +0800, Wei Wang wrote:
> 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>

I'd reorder this before 2/4 this way host can always rely
on the poison feature being supported if free page
tracking is supported.

> ---
> 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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