[PATCH RFC 13/14] vhost: support sharing workers across devs

[Mike Christie <michael.christie@xxxxxxxxxx>]

This allows a worker to handle multiple device's vqs.

TODO:
- How to handle if the devices are in different cgroups/VMs.

Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
---
 drivers/vhost/vhost.c | 18 +++++++-----------
 drivers/vhost/vhost.h |  1 -
 2 files changed, 7 insertions(+), 12 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 7ba0c303bb98..b2d567a4cd53 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -387,12 +387,10 @@ static void vhost_vq_reset(struct vhost_dev *dev,
 static int vhost_worker(void *data)
 {
 	struct vhost_worker *worker = data;
-	struct vhost_dev *dev = worker->dev;
 	struct vhost_work *work, *work_next;
+	struct vhost_dev *dev;
 	struct llist_node *node;
 
-	kthread_use_mm(dev->mm);
-
 	for (;;) {
 		/* mb paired w/ kthread_stop */
 		set_current_state(TASK_INTERRUPTIBLE);
@@ -411,15 +409,20 @@ static int vhost_worker(void *data)
 		smp_wmb();
 		llist_for_each_entry_safe(work, work_next, node, node) {
 			clear_bit(VHOST_WORK_QUEUED, &work->flags);
+			dev = work->dev;
+
+			kthread_use_mm(dev->mm);
+
 			__set_current_state(TASK_RUNNING);
 			kcov_remote_start_common(dev->kcov_handle);
 			work->fn(work);
 			kcov_remote_stop();
 			if (need_resched())
 				schedule();
+
+			kthread_unuse_mm(dev->mm);
 		}
 	}
-	kthread_unuse_mm(dev->mm);
 	return 0;
 }
 
@@ -665,7 +668,6 @@ static struct vhost_worker *vhost_worker_create(struct vhost_dev *dev)
 		return NULL;
 
 	worker->id = dev->num_workers;
-	worker->dev = dev;
 	init_llist_head(&worker->work_list);
 	INIT_LIST_HEAD(&worker->list);
 	refcount_set(&worker->refcount, 1);
@@ -703,12 +705,6 @@ static struct vhost_worker *vhost_worker_find(struct vhost_dev *dev, pid_t pid)
 		if (worker->task->pid != pid)
 			continue;
 
-		/* tmp - next patch allows sharing across devs */
-		if (worker->dev != dev) {
-			spin_unlock(&vhost_workers_lock);
-			return NULL;
-		}
-
 		refcount_inc(&worker->refcount);
 		spin_unlock(&vhost_workers_lock);
 		return worker;
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 051dea4e3ab6..6d97fdf231c2 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -32,7 +32,6 @@ struct vhost_worker {
 	struct llist_head	work_list;
 	struct list_head	list;
 	refcount_t		refcount;
-	struct vhost_dev	*dev;
 	int			id;
 };
 
-- 
2.25.1

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