RE: [PATCH v15 5/5] virtio-balloon: VIRTIO_BALLOON_F_CTRL_VQ

From: Wang, Wei W
Date: Tue Sep 05 2017 - 07:57:24 EST

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Ping for comments if possible. Thanks.

On Monday, August 28, 2017 6:09 PM, Wang, Wei W wrote:
> [PATCH v15 5/5] virtio-balloon: VIRTIO_BALLOON_F_CTRL_VQ
>
> Add a new vq, ctrl_vq, to handle commands between the host and guest.
> With this feature, we will be able to have the control plane and data plane
> separated. In other words, the control related data of each feature will be sent
> via the ctrl_vq cmds, meanwhile each feature may have its own data plane vq.
>
> Free page report is the the first new feature controlled via ctrl_vq, and a new
> cmd class, VIRTIO_BALLOON_CTRLQ_CLASS_FREE_PAGE, is added.
> Currently, this feature has two cmds:
> VIRTIO_BALLOON_FREE_PAGE_F_START: This cmd is sent from host to guest to
> start the free page reporting work.
> VIRTIO_BALLOON_FREE_PAGE_F_STOP: This cmd is used bidirectionally. The
> guest would send the cmd to the host to indicate the reporting work is done.
> The host would send the cmd to the guest to actively request the stop of the
> reporting work.
>
> The free_page_vq is used to transmit the guest free page blocks to the host.
>
> Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
> Signed-off-by: Liang Li <liang.z.li@xxxxxxxxx>
> ---
> drivers/virtio/virtio_balloon.c | 247 +++++++++++++++++++++++++++++++++-
> --
> include/uapi/linux/virtio_balloon.h | 15 +++
> 2 files changed, 242 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index
> 8ecc1d4..1d384a4 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -55,7 +55,13 @@ static struct vfsmount *balloon_mnt;
>
> struct virtio_balloon {
> struct virtio_device *vdev;
> - struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
> + struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *ctrl_vq,
> + *free_page_vq;
> +
> + /* Balloon's own wq for cpu-intensive work items */
> + struct workqueue_struct *balloon_wq;
> + /* The work items submitted to the balloon wq are listed here */
> + struct work_struct report_free_page_work;
>
> /* The balloon servicing is delegated to a freezable workqueue. */
> struct work_struct update_balloon_stats_work; @@ -65,6 +71,9 @@
> struct virtio_balloon {
> spinlock_t stop_update_lock;
> bool stop_update;
>
> + /* Stop reporting free pages */
> + bool report_free_page_stop;
> +
> /* Waiting for host to ack the pages we released. */
> wait_queue_head_t acked;
>
> @@ -93,6 +102,11 @@ struct virtio_balloon {
>
> /* To register callback in oom notifier call chain */
> struct notifier_block nb;
> +
> + /* Host to guest ctrlq cmd buf for free page report */
> + struct virtio_balloon_ctrlq_cmd free_page_cmd_in;
> + /* Guest to Host ctrlq cmd buf for free page report */
> + struct virtio_balloon_ctrlq_cmd free_page_cmd_out;
> };
>
> static struct virtio_device_id id_table[] = { @@ -177,6 +191,26 @@ static void
> send_balloon_page_sg(struct virtio_balloon *vb,
> }
> }
>
> +static void send_free_page_sg(struct virtqueue *vq, void *addr,
> +uint32_t size) {
> + unsigned int len;
> + int err = -ENOSPC;
> +
> + do {
> + if (vq->num_free) {
> + err = add_one_sg(vq, addr, size);
> + /* Sanity check: this can't really happen */
> + WARN_ON(err);
> + if (!err)
> + virtqueue_kick(vq);
> + }
> +
> + /* Release entries if there are */
> + while (virtqueue_get_buf(vq, &len))
> + ;
> + } while (err == -ENOSPC && vq->num_free); }
> +
> /*
> * Send balloon pages in sgs to host. The balloon pages are recorded in the
> * page xbitmap. Each bit in the bitmap corresponds to a page of PAGE_SIZE.
> @@ -525,42 +559,206 @@ static void update_balloon_size_func(struct
> work_struct *work)
> queue_work(system_freezable_wq, work); }
>
> -static int init_vqs(struct virtio_balloon *vb)
> +static bool virtio_balloon_send_free_pages(void *opaque, unsigned long pfn,
> + unsigned long nr_pages)
> +{
> + struct virtio_balloon *vb = (struct virtio_balloon *)opaque;
> + void *addr = (void *)pfn_to_kaddr(pfn);
> + uint32_t len = nr_pages << PAGE_SHIFT;
> +
> + if (vb->report_free_page_stop)
> + return 1;
> +
> + send_free_page_sg(vb->free_page_vq, addr, len);
> +
> + return 0;
> +}
> +
> +static void ctrlq_add_cmd(struct virtqueue *vq,
> + struct virtio_balloon_ctrlq_cmd *cmd,
> + bool inbuf)
> {
> - struct virtqueue *vqs[3];
> - vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
> - static const char * const names[] = { "inflate", "deflate", "stats" };
> - int err, nvqs;
> + struct scatterlist sg;
> + int err;
> +
> + sg_init_one(&sg, cmd, sizeof(struct virtio_balloon_ctrlq_cmd));
> + if (inbuf)
> + err = virtqueue_add_inbuf(vq, &sg, 1, cmd, GFP_KERNEL);
> + else
> + err = virtqueue_add_outbuf(vq, &sg, 1, cmd, GFP_KERNEL);
> +
> + /* Sanity check: this can't really happen */
> + WARN_ON(err);
> +}
>
> +static void ctrlq_send_cmd(struct virtio_balloon *vb,
> + struct virtio_balloon_ctrlq_cmd *cmd,
> + bool inbuf)
> +{
> + struct virtqueue *vq = vb->ctrl_vq;
> +
> + ctrlq_add_cmd(vq, cmd, inbuf);
> + if (!inbuf) {
> + /*
> + * All the input cmd buffers are replenished here.
> + * This is necessary because the input cmd buffers are lost
> + * after live migration. The device needs to rewind all of
> + * them from the ctrl_vq.
> + */
> + ctrlq_add_cmd(vq, &vb->free_page_cmd_in, true);
> + }
> + virtqueue_kick(vq);
> +}
> +
> +static void report_free_page_end(struct virtio_balloon *vb) {
> /*
> - * We expect two virtqueues: inflate and deflate, and
> - * optionally stat.
> + * The host may have already requested to stop the reporting before we
> + * finish, so no need to notify the host in this case.
> */
> - nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ?
> 3 : 2;
> - err = virtio_find_vqs(vb->vdev, nvqs, vqs, callbacks, names, NULL);
> + if (vb->report_free_page_stop)
> + return;
> +
> + vb->free_page_cmd_out.class =
> VIRTIO_BALLOON_CTRLQ_CLASS_FREE_PAGE;
> + vb->free_page_cmd_out.cmd = VIRTIO_BALLOON_FREE_PAGE_F_STOP;
> + ctrlq_send_cmd(vb, &vb->free_page_cmd_out, false);
> + vb->report_free_page_stop = true;
> +}
> +
> +static void report_free_page(struct work_struct *work) {
> + struct virtio_balloon *vb;
> +
> + vb = container_of(work, struct virtio_balloon, report_free_page_work);
> + walk_free_mem_block(vb, 0, &virtio_balloon_send_free_pages);
> + report_free_page_end(vb);
> +}
> +
> +static void ctrlq_handle(struct virtqueue *vq) {
> + struct virtio_balloon *vb = vq->vdev->priv;
> + struct virtio_balloon_ctrlq_cmd *cmd;
> + unsigned int len;
> +
> + cmd = (struct virtio_balloon_ctrlq_cmd *)virtqueue_get_buf(vq, &len);
> +
> + if (unlikely(!cmd))
> + return;
> +
> + /* The outbuf is sent by the host for recycling, so just return. */
> + if (cmd == &vb->free_page_cmd_out)
> + return;
> +
> + switch (cmd->class) {
> + case VIRTIO_BALLOON_CTRLQ_CLASS_FREE_PAGE:
> + if (cmd->cmd == VIRTIO_BALLOON_FREE_PAGE_F_STOP) {
> + vb->report_free_page_stop = true;
> + } else if (cmd->cmd == VIRTIO_BALLOON_FREE_PAGE_F_START)
> {
> + vb->report_free_page_stop = false;
> + queue_work(vb->balloon_wq, &vb-
> >report_free_page_work);
> + }
> + vb->free_page_cmd_in.class =
> +
> VIRTIO_BALLOON_CTRLQ_CLASS_FREE_PAGE;
> + ctrlq_send_cmd(vb, &vb->free_page_cmd_in, true);
> + break;
> + default:
> + dev_warn(&vb->vdev->dev, "%s: cmd class not supported\n",
> + __func__);
> + }
> +}
> +
> +static int init_vqs(struct virtio_balloon *vb) {
> + struct virtqueue **vqs;
> + vq_callback_t **callbacks;
> + const char **names;
> + struct scatterlist sg;
> + int i, nvqs, err = -ENOMEM;
> +
> + /* Inflateq and deflateq are used unconditionally */
> + nvqs = 2;
> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ))
> + nvqs++;
> + /* If ctrlq is enabled, the free page vq will also be created */
> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_CTRL_VQ))
> + nvqs += 2;
> +
> + /* Allocate space for find_vqs parameters */
> + vqs = kcalloc(nvqs, sizeof(*vqs), GFP_KERNEL);
> + if (!vqs)
> + goto err_vq;
> + callbacks = kmalloc_array(nvqs, sizeof(*callbacks), GFP_KERNEL);
> + if (!callbacks)
> + goto err_callback;
> + names = kmalloc_array(nvqs, sizeof(*names), GFP_KERNEL);
> + if (!names)
> + goto err_names;
> +
> + callbacks[0] = balloon_ack;
> + names[0] = "inflate";
> + callbacks[1] = balloon_ack;
> + names[1] = "deflate";
> +
> + i = 2;
> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
> + callbacks[i] = stats_request;
> + names[i] = "stats";
> + i++;
> + }
> +
> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_CTRL_VQ)) {
> + callbacks[i] = ctrlq_handle;
> + names[i++] = "ctrlq";
> + callbacks[i] = NULL;
> + names[i] = "free_page_vq";
> + }
> +
> + err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names,
> + NULL, NULL);
> if (err)
> - return err;
> + goto err_find;
>
> vb->inflate_vq = vqs[0];
> vb->deflate_vq = vqs[1];
> + i = 2;
> if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
> - struct scatterlist sg;
> - unsigned int num_stats;
> - vb->stats_vq = vqs[2];
> -
> + vb->stats_vq = vqs[i++];
> /*
> * Prime this virtqueue with one buffer so the hypervisor can
> * use it to signal us later (it can't be broken yet!).
> */
> - num_stats = update_balloon_stats(vb);
> -
> - sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
> + sg_init_one(&sg, vb->stats, sizeof(vb->stats));
> if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
> - < 0)
> - BUG();
> + < 0) {
> + dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
> + __func__);
> + goto err_find;
> + }
> virtqueue_kick(vb->stats_vq);
> }
> +
> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_CTRL_VQ)) {
> + vb->ctrl_vq = vqs[i++];
> + vb->free_page_vq = vqs[i];
> + /* Prime the ctrlq with an inbuf for the host to send a cmd */
> + vb->free_page_cmd_in.class =
> +
> VIRTIO_BALLOON_CTRLQ_CLASS_FREE_PAGE;
> + ctrlq_send_cmd(vb, &vb->free_page_cmd_in, true);
> + }
> +
> + kfree(names);
> + kfree(callbacks);
> + kfree(vqs);
> return 0;
> +
> +err_find:
> + kfree(names);
> +err_names:
> + kfree(callbacks);
> +err_callback:
> + kfree(vqs);
> +err_vq:
> + return err;
> }
>
> #ifdef CONFIG_BALLOON_COMPACTION
> @@ -689,6 +887,13 @@ static int virtballoon_probe(struct virtio_device *vdev)
> if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_SG))
> xb_init(&vb->page_xb);
>
> + if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_CTRL_VQ)) {
> + vb->balloon_wq = alloc_workqueue("balloon-wq",
> + WQ_FREEZABLE |
> WQ_CPU_INTENSIVE, 0);
> + INIT_WORK(&vb->report_free_page_work, report_free_page);
> + vb->report_free_page_stop = true;
> + }
> +
> vb->nb.notifier_call = virtballoon_oom_notify;
> vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
> err = register_oom_notifier(&vb->nb);
> @@ -753,6 +958,7 @@ static void virtballoon_remove(struct virtio_device
> *vdev)
> spin_unlock_irq(&vb->stop_update_lock);
> cancel_work_sync(&vb->update_balloon_size_work);
> cancel_work_sync(&vb->update_balloon_stats_work);
> + cancel_work_sync(&vb->report_free_page_work);
>
> remove_common(vb);
> #ifdef CONFIG_BALLOON_COMPACTION
> @@ -806,6 +1012,7 @@ static unsigned int features[] = {
> VIRTIO_BALLOON_F_STATS_VQ,
> VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
> VIRTIO_BALLOON_F_SG,
> + VIRTIO_BALLOON_F_CTRL_VQ,
> };
>
> static struct virtio_driver virtio_balloon_driver = { diff --git
> a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
> index 37780a7..dbf0616 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_SG 3 /* Use sg instead of PFN lists
> */
> +#define VIRTIO_BALLOON_F_CTRL_VQ 4 /* Control Virtqueue */
>
> /* Size of a PFN in the balloon interface. */ #define
> VIRTIO_BALLOON_PFN_SHIFT 12 @@ -83,4 +84,18 @@ struct
> virtio_balloon_stat {
> __virtio64 val;
> } __attribute__((packed));
>
> +enum {
> + VIRTIO_BALLOON_CTRLQ_CLASS_FREE_PAGE = 0,
> + VIRTIO_BALLOON_CTRLQ_CLASS_MAX,
> +};
> +
> +struct virtio_balloon_ctrlq_cmd {
> + __virtio32 class;
> + __virtio32 cmd;
> +};
> +
> +/* Ctrlq commands related to VIRTIO_BALLOON_CTRLQ_CLASS_FREE_PAGE */
> +#define VIRTIO_BALLOON_FREE_PAGE_F_STOP 0
> +#define VIRTIO_BALLOON_FREE_PAGE_F_START 1
> +
> #endif /* _LINUX_VIRTIO_BALLOON_H */
> --
> 2.7.4

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