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

[Stefano Garzarella]

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 <l...@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