linux-kernel - Re: [PATCH v8 4/8] vhost: Introduce vhost_worker_ops in vhost

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Message-ID: <3hsgi4a2kj5fg65zz7q463ypxbstf2x73avupayyrexjonkheo@utoyktego6as>
Date: Tue, 1 Apr 2025 15:48:12 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Cindy Lu <lulu@...hat.com>
Cc: jasowang@...hat.com, mst@...hat.com, michael.christie@...cle.com, 
	linux-kernel@...r.kernel.org, virtualization@...ts.linux-foundation.org, 
	netdev@...r.kernel.org
Subject: Re: [PATCH v8 4/8] vhost: Introduce vhost_worker_ops in vhost_worker

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@...hat.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
>