This patch allows userspace to change the vq to worker mapping while it's
in use so tools can do this setup post device creation if needed.
Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
---
drivers/vhost/vhost.c | 102 +++++++++++++++++++++++++------------
drivers/vhost/vhost.h | 2 +-
include/uapi/linux/vhost.h | 2 +-
3 files changed, 71 insertions(+), 35 deletions(-)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 20bf67a846f1..f47710a77853 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -232,12 +232,9 @@ void vhost_poll_stop(struct vhost_poll *poll)
}
EXPORT_SYMBOL_GPL(vhost_poll_stop);
-static void vhost_work_queue_on(struct vhost_worker *worker,
- struct vhost_work *work)
+static void vhost_worker_work_queue(struct vhost_worker *worker,
+ struct vhost_work *work)
{
- if (!worker)
- return;
-
if (!test_and_set_bit(VHOST_WORK_QUEUED, &work->flags)) {
/* We can only add the work to the list after we're
* sure it was not in the list.
@@ -248,31 +245,45 @@ static void vhost_work_queue_on(struct vhost_worker *worker,
}
}
-static void vhost_work_flush_on(struct vhost_worker *worker)
+void vhost_vq_work_queue(struct vhost_virtqueue *vq, struct vhost_work *work)
{
- struct vhost_flush_struct flush;
+ struct vhost_worker *worker;
- if (!worker)
- return;
+ rcu_read_lock();
+ worker = rcu_dereference(vq->worker);
+ if (worker)
+ vhost_worker_work_queue(worker, work);
+ rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(vhost_vq_work_queue);
- init_completion(&flush.wait_event);
- vhost_work_init(&flush.work, vhost_flush_work);
+static void vhost_worker_flush_queue(struct vhost_worker *worker,
+ struct vhost_flush_struct *flush)
+{
+ init_completion(&flush->wait_event);
+ vhost_work_init(&flush->work, vhost_flush_work);
- vhost_work_queue_on(worker, &flush.work);
- wait_for_completion(&flush.wait_event);
+ vhost_worker_work_queue(worker, &flush->work);
}
void vhost_vq_work_flush(struct vhost_virtqueue *vq)
{
- vhost_work_flush_on(vq->worker);
-}
-EXPORT_SYMBOL_GPL(vhost_vq_work_flush);
+ struct vhost_flush_struct flush;
+ struct vhost_worker *worker;
-void vhost_vq_work_queue(struct vhost_virtqueue *vq, struct vhost_work *work)
-{
- vhost_work_queue_on(vq->worker, work);
+ rcu_read_lock();
+ worker = rcu_dereference(vq->worker);
+ if (!worker) {
+ rcu_read_unlock();
+ return;
+ }
+
+ vhost_worker_flush_queue(worker, &flush);
+ rcu_read_unlock();
+
+ wait_for_completion(&flush.wait_event);
}
-EXPORT_SYMBOL_GPL(vhost_vq_work_queue);
+EXPORT_SYMBOL_GPL(vhost_vq_work_flush);
/* Flush any work that has been scheduled. When calling this, don't hold any
* locks that are also used by the callback. */
@@ -285,7 +296,16 @@ EXPORT_SYMBOL_GPL(vhost_poll_flush);
/* A lockless hint for busy polling code to exit the loop */
bool vhost_vq_has_work(struct vhost_virtqueue *vq)
{
- return vq->worker && !llist_empty(&vq->worker->work_list);
+ struct vhost_worker *worker;
+ bool has_work = false;
+
+ rcu_read_lock();
+ worker = rcu_dereference(vq->worker);
+ if (worker && !llist_empty(&worker->work_list))
+ has_work = true;
+ rcu_read_unlock();
+
+ return has_work;
}
EXPORT_SYMBOL_GPL(vhost_vq_has_work);
@@ -510,7 +530,7 @@ void vhost_dev_init(struct vhost_dev *dev,
vq->log = NULL;
vq->indirect = NULL;
vq->heads = NULL;
- vq->worker = NULL;
+ rcu_assign_pointer(vq->worker, NULL);
vq->dev = dev;
mutex_init(&vq->mutex);
vhost_vq_reset(dev, vq);
@@ -590,11 +610,32 @@ static void vhost_worker_put(struct vhost_dev *dev, struct vhost_worker *worker)
kfree(worker);
}
-static void vhost_vq_detach_worker(struct vhost_virtqueue *vq)
+static void vhost_vq_swap_worker(struct vhost_virtqueue *vq,
+ struct vhost_worker *new_worker, bool flush)
{
- if (vq->worker)
- vhost_worker_put(vq->dev, vq->worker);
- vq->worker = NULL;
+ struct vhost_flush_struct flush_work;
+ struct vhost_worker *old_worker;
+
+ old_worker = rcu_dereference_check(vq->worker,
+ lockdep_is_held(&vq->dev->mutex));
+ rcu_assign_pointer(vq->worker, new_worker);
+
+ if (!old_worker)
+ return;
+
+ if (flush) {
+ /*
+ * For dev cleanup we won't have work running, but for the
+ * dynamic attach case we might so make sure we see the new
+ * worker and there is no work in the old worker.
+ */
+ synchronize_rcu();
+
+ vhost_worker_flush_queue(old_worker, &flush_work);
+ wait_for_completion(&flush_work.wait_event);
+ }
+
+ vhost_worker_put(vq->dev, old_worker);
}
static int vhost_workers_idr_iter(int id, void *worker, void *dev)
@@ -611,7 +652,7 @@ static void vhost_workers_free(struct vhost_dev *dev)
return;
for (i = 0; i < dev->nvqs; i++)
- vhost_vq_detach_worker(dev->vqs[i]);
+ vhost_vq_swap_worker(dev->vqs[i], NULL, false);
idr_for_each(&dev->worker_idr, vhost_workers_idr_iter, dev);
}
@@ -667,18 +708,13 @@ static int vhost_vq_attach_worker(struct vhost_virtqueue *vq,
if (!dev->use_worker)
return -EINVAL;
- /* We don't support setting a worker on an active vq */
- if (vq->private_data)
- return -EBUSY;
-
worker = idr_find(&dev->worker_idr, info->worker_id);
if (!worker)
return -ENODEV;
refcount_inc(&worker->refcount);
- vhost_vq_detach_worker(vq);
- vq->worker = worker;
+ vhost_vq_swap_worker(vq, worker, true);
return 0;
}
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index b3786e3537f1..607e95887942 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -81,7 +81,7 @@ struct vhost_vring_call {
/* The virtqueue structure describes a queue attached to a device. */
struct vhost_virtqueue {
struct vhost_dev *dev;
- struct vhost_worker *worker;
+ struct vhost_worker __rcu *worker;
/* The actual ring of buffers. */
struct mutex mutex;
diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index 117ea92b3925..e0221c8ce877 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h
@@ -88,7 +88,7 @@
#define VHOST_SET_VRING_ENDIAN _IOW(VHOST_VIRTIO, 0x13, struct vhost_vring_state)
#define VHOST_GET_VRING_ENDIAN _IOW(VHOST_VIRTIO, 0x14, struct vhost_vring_state)
/* Attach a vhost_worker created with VHOST_NEW_WORKER to one of the device's
- * virtqueues. This must be done before the virtqueue is active.
+ * virtqueues.
*/
#define VHOST_ATTACH_VRING_WORKER _IOR(VHOST_VIRTIO, 0x15, \
struct vhost_vring_worker)
--
2.25.1
