Re: [PATCH v8 4/8] vhost: Introduce vhost_worker_ops in vhost_worker

Cindy Lu
2025-04-07T03:14:22Z

On Tue, Apr 1, 2025 at 9:48 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
>
> On Fri, Mar 28, 2025 at 06:02:48PM +0800, Cindy Lu wrote:
> >Abstract vhost worker operations (create/stop/wakeup) into an ops
> >structure to prepare for kthread mode support.
> >
> >Signed-off-by: Cindy Lu <lulu@redhat.com>
> >---
> > drivers/vhost/vhost.c | 63 ++++++++++++++++++++++++++++++-------------
> > drivers/vhost/vhost.h | 11 ++++++++
> > 2 files changed, 56 insertions(+), 18 deletions(-)
> >
> >diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> >index 20571bd6f7bd..c162ad772f8f 100644
> >--- a/drivers/vhost/vhost.c
> >+++ b/drivers/vhost/vhost.c
> >@@ -243,7 +243,7 @@ static void vhost_worker_queue(struct vhost_worker *worker,
> > * test_and_set_bit() implies a memory barrier.
> > */
> > llist_add(&work->node, &worker->work_list);
> >- vhost_task_wake(worker->vtsk);
> >+ worker->ops->wakeup(worker);
> > }
> > }
> >
> >@@ -706,7 +706,7 @@ static void vhost_worker_destroy(struct vhost_dev *dev,
> >
> > WARN_ON(!llist_empty(&worker->work_list));
> > xa_erase(&dev->worker_xa, worker->id);
> >- vhost_task_stop(worker->vtsk);
> >+ worker->ops->stop(worker);
> > kfree(worker);
> > }
> >
> >@@ -729,42 +729,69 @@ static void vhost_workers_free(struct vhost_dev *dev)
> > xa_destroy(&dev->worker_xa);
> > }
> >
> >+static void vhost_task_wakeup(struct vhost_worker *worker)
> >+{
> >+ return vhost_task_wake(worker->vtsk);
> >+}
> >+
> >+static void vhost_task_do_stop(struct vhost_worker *worker)
> >+{
> >+ return vhost_task_stop(worker->vtsk);
> >+}
> >+
> >+static int vhost_task_worker_create(struct vhost_worker *worker,
> >+ struct vhost_dev *dev, const char *name)
> >+{
> >+ struct vhost_task *vtsk;
> >+ u32 id;
> >+ int ret;
> >+
> >+ vtsk = vhost_task_create(vhost_run_work_list, vhost_worker_killed,
> >+ worker, name);
> >+ if (IS_ERR(vtsk))
> >+ return PTR_ERR(vtsk);
> >+
> >+ worker->vtsk = vtsk;
> >+ vhost_task_start(vtsk);
> >+ ret = xa_alloc(&dev->worker_xa, &id, worker, xa_limit_32b, GFP_KERNEL);
> >+ if (ret < 0) {
> >+ vhost_task_do_stop(worker);
> >+ return ret;
> >+ }
>
> In the final code, xa_alloc() is duplicated among the functions that
> create ktrhead or task, might it make sense to leave it out and do it in
> vhost_worker_create() ?
>
> Thanks,
> Stefano
>
Thanks a lot Stefano. I previously tried moving xa_alloc() out, but
that made the code strange.
I think keeping xa_alloc() in the create_ops function completes the
job in a single function, and maybe it could be used in some other
functions in the future
thanks
cindy

> >+ worker->id = id;
> >+ return 0;
> >+}
> >+
> >+static const struct vhost_worker_ops vhost_task_ops = {
> >+ .create = vhost_task_worker_create,
> >+ .stop = vhost_task_do_stop,
> >+ .wakeup = vhost_task_wakeup,
> >+};
> >+
> > static struct vhost_worker *vhost_worker_create(struct vhost_dev *dev)
> > {
> > struct vhost_worker *worker;
> >- struct vhost_task *vtsk;
> > char name[TASK_COMM_LEN];
> > int ret;
> >- u32 id;
> >+ const struct vhost_worker_ops *ops = &vhost_task_ops;
> >
> > worker = kzalloc(sizeof(*worker), GFP_KERNEL_ACCOUNT);
> > if (!worker)
> > return NULL;
> >
> > worker->dev = dev;
> >+ worker->ops = ops;
> > snprintf(name, sizeof(name), "vhost-%d", current->pid);
> >
> >- vtsk = vhost_task_create(vhost_run_work_list, vhost_worker_killed,
> >- worker, name);
> >- if (IS_ERR(vtsk))
> >- goto free_worker;
> >-
> > mutex_init(&worker->mutex);
> > init_llist_head(&worker->work_list);
> > worker->kcov_handle = kcov_common_handle();
> >- worker->vtsk = vtsk;
> >-
> >- vhost_task_start(vtsk);
> >-
> >- ret = xa_alloc(&dev->worker_xa, &id, worker, xa_limit_32b, GFP_KERNEL);
> >+ ret = ops->create(worker, dev, name);
> > if (ret < 0)
> >- goto stop_worker;
> >- worker->id = id;
> >+ goto free_worker;
> >
> > return worker;
> >
> >-stop_worker:
> >- vhost_task_stop(vtsk);
> > free_worker:
> > kfree(worker);
> > return NULL;
> >diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> >index 19bb94922a0e..98895e299efa 100644
> >--- a/drivers/vhost/vhost.h
> >+++ b/drivers/vhost/vhost.h
> >@@ -26,6 +26,16 @@ struct vhost_work {
> > unsigned long flags;
> > };
> >
> >+struct vhost_worker;
> >+struct vhost_dev;
> >+
> >+struct vhost_worker_ops {
> >+ int (*create)(struct vhost_worker *worker, struct vhost_dev *dev,
> >+ const char *name);
> >+ void (*stop)(struct vhost_worker *worker);
> >+ void (*wakeup)(struct vhost_worker *worker);
> >+};
> >+
> > struct vhost_worker {
> > struct vhost_task *vtsk;
> > struct vhost_dev *dev;
> >@@ -36,6 +46,7 @@ struct vhost_worker {
> > u32 id;
> > int attachment_cnt;
> > bool killed;
> >+ const struct vhost_worker_ops *ops;
> > };
> >
> > /* Poll a file (eventfd or socket) */
> >--
> >2.45.0
> >
>