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

[Mike Christie]

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.chris...@oracle.com>
---
 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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