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

Stefano Garzarella
2025-04-01T13:48:20Z

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

>+ 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
>