On Tue, May 25, 2021 at 01:05:54PM -0500, Mike Christie wrote:
> -void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
> +static void vhost_work_queue_on(struct vhost_work *work,
> + struct vhost_worker *worker)
> {
> - if (!dev->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.
> * test_and_set_bit() implies a memory barrier.
> */
> - llist_add(&work->node, &dev->worker->work_list);
> - wake_up_process(dev->worker->task);
> + llist_add(&work->node, &worker->work_list);
> + wake_up_process(worker->task);
> }
> }
> +
> +void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
When should this function still be used? A doc comment contrasting it to
vhost_work_queue_on() would be helpful. I would expect callers to switch
to that instead of queuing work on dev->workers[0].
> /* A lockless hint for busy polling code to exit the loop */
> bool vhost_has_work(struct vhost_dev *dev)
> {
> - return dev->worker && !llist_empty(&dev->worker->work_list);
> + int i;
> +
> + for (i = 0; i < dev->num_workers; i++) {
> + if (!llist_empty(&dev->workers[i]->work_list))
> + return true;
> + }
> +
> + return false;
> }
> EXPORT_SYMBOL_GPL(vhost_has_work);
It's probably not necessary to poll all workers:
drivers/vhost/net.c calls vhost_has_work() to busy poll a specific
virtqueue. If the vq:worker mapping is 1:1 or N:1 then vhost_has_work()
should be extended to include the struct vhost_virtqueue so we can poll
just that vq worker's work_list.
> /* Caller must have device mutex */
> static int vhost_worker_try_create_def(struct vhost_dev *dev)
> {
> - if (!dev->use_worker || dev->worker)
> + struct vhost_worker *worker;
> +
> + if (!dev->use_worker || dev->workers)
> return 0;
>
> - return vhost_worker_create(dev);
> + dev->workers = kcalloc(1, sizeof(struct vhost_worker *), GFP_KERNEL);
GFP_KERNEL_ACCOUNT so that vhost memory associated with a process (the
one that invoked the ioctl) is accounted? This may get trickier if the
workers are shared between processes.
The same applies for struct vhost_worker in vhost_worker_create().
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