vhost: dynamically allocate vhost_worker

This patchset allows us to allocate multiple workers, so this has us
move from the vhost_worker that's embedded in the vhost_dev to
dynamically allocating it.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Message-Id: <20230626232307.97930-3-michael.christie@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 82966ff..dfd96cf 100644 (file)
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -235,36 +235,40 @@ void vhost_dev_flush(struct vhost_dev *dev)
 {
        struct vhost_flush_struct flush;
 
-       if (dev->worker.vtsk) {
-               init_completion(&flush.wait_event);
-               vhost_work_init(&flush.work, vhost_flush_work);
+       init_completion(&flush.wait_event);
+       vhost_work_init(&flush.work, vhost_flush_work);
 
-               vhost_work_queue(dev, &flush.work);
+       if (vhost_work_queue(dev, &flush.work))
                wait_for_completion(&flush.wait_event);
-       }
 }
 EXPORT_SYMBOL_GPL(vhost_dev_flush);
 
-void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
+bool vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
 {
-       if (!dev->worker.vtsk)
-               return;
-
+       if (!dev->worker)
+               return false;
+       /*
+        * vsock can queue while we do a VHOST_SET_OWNER, so we have a smp_wmb
+        * when setting up the worker. We don't have a smp_rmb here because
+        * test_and_set_bit gives us a mb already.
+        */
        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.
                 * test_and_set_bit() implies a memory barrier.
                 */
-               llist_add(&work->node, &dev->worker.work_list);
-               vhost_task_wake(dev->worker.vtsk);
+               llist_add(&work->node, &dev->worker->work_list);
+               vhost_task_wake(dev->worker->vtsk);
        }
+
+       return true;
 }
 EXPORT_SYMBOL_GPL(vhost_work_queue);
 
 /* A lockless hint for busy polling code to exit the loop */
 bool vhost_has_work(struct vhost_dev *dev)
 {
-       return !llist_empty(&dev->worker.work_list);
+       return !llist_empty(&dev->worker->work_list);
 }
 EXPORT_SYMBOL_GPL(vhost_has_work);
 
@@ -458,8 +462,7 @@ void vhost_dev_init(struct vhost_dev *dev,
        dev->umem = NULL;
        dev->iotlb = NULL;
        dev->mm = NULL;
-       memset(&dev->worker, 0, sizeof(dev->worker));
-       init_llist_head(&dev->worker.work_list);
+       dev->worker = NULL;
        dev->iov_limit = iov_limit;
        dev->weight = weight;
        dev->byte_weight = byte_weight;
@@ -533,30 +536,47 @@ static void vhost_detach_mm(struct vhost_dev *dev)
 
 static void vhost_worker_free(struct vhost_dev *dev)
 {
-       if (!dev->worker.vtsk)
+       if (!dev->worker)
                return;
 
-       WARN_ON(!llist_empty(&dev->worker.work_list));
-       vhost_task_stop(dev->worker.vtsk);
-       dev->worker.kcov_handle = 0;
-       dev->worker.vtsk = NULL;
+       WARN_ON(!llist_empty(&dev->worker->work_list));
+       vhost_task_stop(dev->worker->vtsk);
+       kfree(dev->worker);
+       dev->worker = NULL;
 }
 
 static int vhost_worker_create(struct vhost_dev *dev)
 {
+       struct vhost_worker *worker;
        struct vhost_task *vtsk;
        char name[TASK_COMM_LEN];
 
+       worker = kzalloc(sizeof(*worker), GFP_KERNEL_ACCOUNT);
+       if (!worker)
+               return -ENOMEM;
+
        snprintf(name, sizeof(name), "vhost-%d", current->pid);
 
-       vtsk = vhost_task_create(vhost_worker, &dev->worker, name);
+       vtsk = vhost_task_create(vhost_worker, worker, name);
        if (!vtsk)
-               return -ENOMEM;
+               goto free_worker;
+
+       init_llist_head(&worker->work_list);
+       worker->kcov_handle = kcov_common_handle();
+       worker->vtsk = vtsk;
+       /*
+        * vsock can already try to queue so make sure llist and vtsk are both
+        * set before vhost_work_queue sees dev->worker is set.
+        */
+       smp_wmb();
+       dev->worker = worker;
 
-       dev->worker.kcov_handle = kcov_common_handle();
-       dev->worker.vtsk = vtsk;
        vhost_task_start(vtsk);
        return 0;
+
+free_worker:
+       kfree(worker);
+       return -ENOMEM;
 }
 
 /* Caller should have device mutex */

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index fc900be..cb872cc 100644 (file)
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -44,7 +44,7 @@ struct vhost_poll {
 };
 
 void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn);
-void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work);
+bool vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work);
 bool vhost_has_work(struct vhost_dev *dev);
 
 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
@@ -158,7 +158,7 @@ struct vhost_dev {
        struct vhost_virtqueue **vqs;
        int nvqs;
        struct eventfd_ctx *log_ctx;
-       struct vhost_worker worker;
+       struct vhost_worker *worker;
        struct vhost_iotlb *umem;
        struct vhost_iotlb *iotlb;
        spinlock_t iotlb_lock;