[PATCH v12 8/8] virtio-balloon: VIRTIO_BALLOON_F_CMD_VQ

From: Wei Wang
Date: Wed Jul 12 2017 - 08:48:12 EST

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) {
+ /*
+ * 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