On Wed, Jul 12, 2017 at 08:40:21PM +0800, Wei Wang wrote:
> Add a new vq, cmdq, to handle requests between the device and driver.
>
> This patch implements two commands sent from the device and handled in
> the driver.
> 1) VIRTIO_BALLOON_CMDQ_REPORT_STATS: this command is used to report
> the guest memory statistics to the host. The stats_vq mechanism is not
> used when the cmdq mechanism is enabled.
> 2) VIRTIO_BALLOON_CMDQ_REPORT_UNUSED_PAGES: this command is used to
> report the guest unused pages to the host.
>
> Since now we have a vq to handle multiple commands, we need to keep only
> one vq operation at a time. Here, we change the existing START_USE()
> and END_USE() to lock on each vq operation.
>
> Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
> Signed-off-by: Liang Li <liang.z.li@xxxxxxxxx>
> ---
> drivers/virtio/virtio_balloon.c | 245 ++++++++++++++++++++++++++++++++++--
> drivers/virtio/virtio_ring.c | 25 +++-
> include/linux/virtio.h | 2 +
> include/uapi/linux/virtio_balloon.h | 10 ++
> 4 files changed, 265 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index aa4e7ec..ae91fbf 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -54,11 +54,12 @@ 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, *cmd_vq;
>
> /* The balloon servicing is delegated to a freezable workqueue. */
> struct work_struct update_balloon_stats_work;
> struct work_struct update_balloon_size_work;
> + struct work_struct cmdq_handle_work;
>
> /* Prevent updating balloon when it is being canceled. */
> spinlock_t stop_update_lock;
> @@ -90,6 +91,12 @@ struct virtio_balloon {
> /* Memory statistics */
> struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
>
> + /* Cmdq msg buffer for memory statistics */
> + struct virtio_balloon_cmdq_hdr cmdq_stats_hdr;
> +
> + /* Cmdq msg buffer for reporting ununsed pages */
> + struct virtio_balloon_cmdq_hdr cmdq_unused_page_hdr;
> +
> /* To register callback in oom notifier call chain */
> struct notifier_block nb;
> };
> @@ -485,25 +492,214 @@ static void update_balloon_size_func(struct work_struct *work)
> queue_work(system_freezable_wq, work);
> }
>
> +static unsigned int cmdq_hdr_add(struct virtqueue *vq,
> + struct virtio_balloon_cmdq_hdr *hdr,
> + bool in)
> +{
> + unsigned int id = VIRTQUEUE_DESC_ID_INIT;
> + uint64_t hdr_pa = (uint64_t)virt_to_phys((void *)hdr);
> +
> + virtqueue_add_chain_desc(vq, hdr_pa, sizeof(*hdr), &id, &id, in);
> +
> + /* Deliver the hdr for the host to send commands. */
> + if (in) {
> + hdr->flags = 0;
> + virtqueue_add_chain(vq, id, 0, NULL, hdr, NULL);
> + virtqueue_kick(vq);
> + }
> +
> + return id;
> +}
> +
> +static void cmdq_add_chain_desc(struct virtio_balloon *vb,
> + struct virtio_balloon_cmdq_hdr *hdr,
> + uint64_t addr,
> + uint32_t len,
> + unsigned int *head_id,
> + unsigned int *prev_id)
> +{
> +retry:
> + if (*head_id == VIRTQUEUE_DESC_ID_INIT) {
> + *head_id = cmdq_hdr_add(vb->cmd_vq, hdr, 0);
> + *prev_id = *head_id;
> + }
> +
> + virtqueue_add_chain_desc(vb->cmd_vq, addr, len, head_id, prev_id, 0);
> + if (*head_id == *prev_id) {
That's an ugly way to detect ring full.
> + /*
> + * The VQ was full and kicked to release some descs. Now we
> + * will re-start to build the chain by using the hdr as the
> + * first desc, so we need to detach the desc that was just
> + * added, and re-start to add the hdr.
> + */
> + virtqueue_detach_buf(vb->cmd_vq, *head_id, NULL);
> + *head_id = VIRTQUEUE_DESC_ID_INIT;
> + *prev_id = VIRTQUEUE_DESC_ID_INIT;
> + goto retry;
> + }
> +}
> +
> +static void cmdq_handle_stats(struct virtio_balloon *vb)
> +{
> + unsigned int num_stats,
> + head_id = VIRTQUEUE_DESC_ID_INIT,
> + prev_id = VIRTQUEUE_DESC_ID_INIT;
> + uint64_t addr = (uint64_t)virt_to_phys((void *)vb->stats);
> + uint32_t len;
> +
> + spin_lock(&vb->stop_update_lock);
> + if (!vb->stop_update) {
> + num_stats = update_balloon_stats(vb);
> + len = sizeof(struct virtio_balloon_stat) * num_stats;
> + cmdq_add_chain_desc(vb, &vb->cmdq_stats_hdr, addr, len,
> + &head_id, &prev_id);
> + virtqueue_add_chain(vb->cmd_vq, head_id, 0, NULL, vb, NULL);
> + virtqueue_kick_sync(vb->cmd_vq);
> + }
> + spin_unlock(&vb->stop_update_lock);
> +}
> +
> +static void cmdq_add_unused_page(struct virtio_balloon *vb,
> + struct zone *zone,
> + unsigned int order,
> + unsigned int type,
> + struct page *page,
> + unsigned int *head_id,
> + unsigned int *prev_id)
> +{
> + uint64_t addr;
> + uint32_t len;
> +
> + while (!report_unused_page_block(zone, order, type, &page)) {
> + addr = (u64)page_to_pfn(page) << VIRTIO_BALLOON_PFN_SHIFT;
> + len = (u64)(1 << order) << VIRTIO_BALLOON_PFN_SHIFT;
> + cmdq_add_chain_desc(vb, &vb->cmdq_unused_page_hdr, addr, len,
> + head_id, prev_id);
> + }
> +}
> +
> +static void cmdq_handle_unused_pages(struct virtio_balloon *vb)
> +{
> + struct virtqueue *vq = vb->cmd_vq;
> + unsigned int order = 0, type = 0,
> + head_id = VIRTQUEUE_DESC_ID_INIT,
> + prev_id = VIRTQUEUE_DESC_ID_INIT;
> + struct zone *zone = NULL;
> + struct page *page = NULL;
> +
> + for_each_populated_zone(zone)
> + for_each_migratetype_order(order, type)
> + cmdq_add_unused_page(vb, zone, order, type, page,
> + &head_id, &prev_id);
> +
> + /* Set the cmd completion flag. */
> + vb->cmdq_unused_page_hdr.flags |=
> + cpu_to_le32(VIRTIO_BALLOON_CMDQ_F_COMPLETION);
> + virtqueue_add_chain(vq, head_id, 0, NULL, vb, NULL);
> + virtqueue_kick_sync(vb->cmd_vq);
> +}
> +
> +static void cmdq_handle(struct virtio_balloon *vb)
> +{
> + struct virtio_balloon_cmdq_hdr *hdr;
> + unsigned int len;
> +
> + while ((hdr = (struct virtio_balloon_cmdq_hdr *)
> + virtqueue_get_buf(vb->cmd_vq, &len)) != NULL) {
> + switch (__le32_to_cpu(hdr->cmd)) {
> + case VIRTIO_BALLOON_CMDQ_REPORT_STATS:
> + cmdq_handle_stats(vb);
> + break;
> + case VIRTIO_BALLOON_CMDQ_REPORT_UNUSED_PAGES:
> + cmdq_handle_unused_pages(vb);
> + break;
> + default:
> + dev_warn(&vb->vdev->dev, "%s: wrong cmd\n", __func__);
> + return;
> + }
> + /*
> + * Replenish all the command buffer to the device after a
> + * command is handled. This is for the convenience of the
> + * device to rewind the cmdq to get back all the command
> + * buffer after live migration.
> + */
> + cmdq_hdr_add(vb->cmd_vq, &vb->cmdq_stats_hdr, 1);
> + cmdq_hdr_add(vb->cmd_vq, &vb->cmdq_unused_page_hdr, 1);
> + }
> +}
> +
> +static void cmdq_handle_work_func(struct work_struct *work)
> +{
> + struct virtio_balloon *vb;
> +
> + vb = container_of(work, struct virtio_balloon,
> + cmdq_handle_work);
> + cmdq_handle(vb);
> +}
> +
> +static void cmdq_callback(struct virtqueue *vq)
> +{
> + struct virtio_balloon *vb = vq->vdev->priv;
> +
> + queue_work(system_freezable_wq, &vb->cmdq_handle_work);
> +}
> +
> static int init_vqs(struct virtio_balloon *vb)
> {
> - 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 virtqueue **vqs;
> + vq_callback_t **callbacks;
> + const char **names;
> + int err = -ENOMEM;
> + int nvqs;
> +
> + /* Inflateq and deflateq are used unconditionally */
> + nvqs = 2;
> +
> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_CMD_VQ) ||
> + virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ))
> + nvqs++;
> +
> + /* 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";
>
> /*
> - * We expect two virtqueues: inflate and deflate, and
> - * optionally stat.
> + * The stats_vq is used only when cmdq is not supported (or disabled)
> + * by the device.
> */
> - 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 (err)
> - return err;
> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_CMD_VQ)) {
> + callbacks[2] = cmdq_callback;
> + names[2] = "cmdq";
> + } else if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
> + callbacks[2] = stats_request;
> + names[2] = "stats";
> + }
>
> + err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks,
> + names, NULL, NULL);
> + if (err)
> + goto err_find;
> vb->inflate_vq = vqs[0];
> vb->deflate_vq = vqs[1];
> - if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
> +
> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_CMD_VQ)) {
> + vb->cmd_vq = vqs[2];
> + /* Prime the cmdq with the header buffer. */
> + cmdq_hdr_add(vb->cmd_vq, &vb->cmdq_stats_hdr, 1);
> + cmdq_hdr_add(vb->cmd_vq, &vb->cmdq_unused_page_hdr, 1);
> + } else if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
> struct scatterlist sg;
> unsigned int num_stats;
> vb->stats_vq = vqs[2];
> @@ -520,6 +716,16 @@ static int init_vqs(struct virtio_balloon *vb)
> BUG();
> virtqueue_kick(vb->stats_vq);
> }
> +
> +err_find:
> + kfree(names);
> +err_names:
> + kfree(callbacks);
> +err_callback:
> + kfree(vqs);
> +err_vq:
> + return err;
> +
> return 0;
> }
>
> @@ -640,7 +846,18 @@ static int virtballoon_probe(struct virtio_device *vdev)
> goto out;
> }
>
> - INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
> + if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_CMD_VQ)) {
> + vb->cmdq_stats_hdr.cmd =
> + cpu_to_le32(VIRTIO_BALLOON_CMDQ_REPORT_STATS);
> + vb->cmdq_stats_hdr.flags = 0;
> + vb->cmdq_unused_page_hdr.cmd =
> + cpu_to_le32(VIRTIO_BALLOON_CMDQ_REPORT_UNUSED_PAGES);
> + vb->cmdq_unused_page_hdr.flags = 0;
> + INIT_WORK(&vb->cmdq_handle_work, cmdq_handle_work_func);
> + } else if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
> + INIT_WORK(&vb->update_balloon_stats_work,
> + update_balloon_stats_func);
> + }
> INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
> spin_lock_init(&vb->stop_update_lock);
> vb->stop_update = false;
> @@ -722,6 +939,7 @@ 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->cmdq_handle_work);
>
> xb_empty(&vb->page_xb);
> remove_common(vb);
> @@ -776,6 +994,7 @@ static unsigned int features[] = {
> VIRTIO_BALLOON_F_STATS_VQ,
> VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
> VIRTIO_BALLOON_F_SG,
> + VIRTIO_BALLOON_F_CMD_VQ,
> };
>
> static struct virtio_driver virtio_balloon_driver = {
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index b9d7e10..793de12 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -52,8 +52,13 @@
> "%s:"fmt, (_vq)->vq.name, ##args); \
> (_vq)->broken = true; \
> } while (0)
> -#define START_USE(vq)
> -#define END_USE(vq)
> +#define START_USE(_vq) \
> + do { \
> + while ((_vq)->in_use) \
> + cpu_relax(); \
> + (_vq)->in_use = __LINE__; \
> + } while (0)
> +#define END_USE(_vq) ((_vq)->in_use = 0)
> #endif
>
> struct vring_desc_state {
> @@ -101,9 +106,9 @@ struct vring_virtqueue {
> size_t queue_size_in_bytes;
> dma_addr_t queue_dma_addr;
>
> -#ifdef DEBUG
> /* They're supposed to lock for us. */
> unsigned int in_use;
> +#ifdef DEBUG
>
> /* Figure out if their kicks are too delayed. */
> bool last_add_time_valid;
> @@ -845,6 +850,18 @@ static void detach_buf(struct vring_virtqueue *vq, unsigned int head,
> }
> }
>
> +void virtqueue_detach_buf(struct virtqueue *_vq, unsigned int head, void **ctx)
> +{
> + struct vring_virtqueue *vq = to_vvq(_vq);
> +
> + START_USE(vq);
> +
> + detach_buf(vq, head, ctx);
> +
> + END_USE(vq);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_detach_buf);
> +
> static inline bool more_used(const struct vring_virtqueue *vq)
> {
> return vq->last_used_idx != virtio16_to_cpu(vq->vq.vdev, vq->vring.used->idx);
> @@ -1158,8 +1175,8 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
> vq->avail_idx_shadow = 0;
> vq->num_added = 0;
> list_add_tail(&vq->vq.list, &vdev->vqs);
> + vq->in_use = 0;
> #ifdef DEBUG
> - vq->in_use = false;
> vq->last_add_time_valid = false;
> #endif
>
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index 9f27101..9df480b 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -88,6 +88,8 @@ void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len);
> void *virtqueue_get_buf_ctx(struct virtqueue *vq, unsigned int *len,
> void **ctx);
>
> +void virtqueue_detach_buf(struct virtqueue *_vq, unsigned int head, void **ctx);
> +
> void virtqueue_disable_cb(struct virtqueue *vq);
>
> bool virtqueue_enable_cb(struct virtqueue *vq);
> diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
> index 37780a7..b38c370 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_CMD_VQ 4 /* Command virtqueue */
>
> /* Size of a PFN in the balloon interface. */
> #define VIRTIO_BALLOON_PFN_SHIFT 12
> @@ -83,4 +84,13 @@ struct virtio_balloon_stat {
> __virtio64 val;
> } __attribute__((packed));
>
> +struct virtio_balloon_cmdq_hdr {
> +#define VIRTIO_BALLOON_CMDQ_REPORT_STATS 0
> +#define VIRTIO_BALLOON_CMDQ_REPORT_UNUSED_PAGES 1
> + __le32 cmd;
> +/* Flag to indicate the completion of handling a command */
> +#define VIRTIO_BALLOON_CMDQ_F_COMPLETION 1
> + __le32 flags;
> +};
> +
> #endif /* _LINUX_VIRTIO_BALLOON_H */
> --
> 2.7.4
