linux-kernel - Re: [PATCH v8 5/8] vhost: Reintroduce kthread mode support in vhost

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Message-ID: <qtii7gazb52fuvkeiymllkapnd3l3ji6ht7y7cfegybreavmit@h6bvfhwpghg6>
Date: Tue, 1 Apr 2025 15:51:42 +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 5/8] vhost: Reintroduce kthread mode support in vhost

On Fri, Mar 28, 2025 at 06:02:49PM +0800, Cindy Lu wrote:
>This commit restores the previously removed functions kthread
>wake/stop/create, and use ops structure vhost_worker_ops to
>manage worker wakeup, stop and creation. The function
>vhost_worker_create initializes these ops pointers based on
>the value of inherit_owner
>
>The old function was remove in

nit: s/remove/removed

>commit 6e890c5d5021 ("vhost: use vhost_tasks for worker threads")
>
>Signed-off-by: Cindy Lu <lulu@...hat.com>
>---
> drivers/vhost/vhost.c | 48 ++++++++++++++++++++++++++++++++++++++++++-
> drivers/vhost/vhost.h |  1 +
> 2 files changed, 48 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>index c162ad772f8f..be97028a8baf 100644
>--- a/drivers/vhost/vhost.c
>+++ b/drivers/vhost/vhost.c
>@@ -734,11 +734,21 @@ static void vhost_task_wakeup(struct vhost_worker *worker)
> 	return vhost_task_wake(worker->vtsk);
> }
>
>+static void vhost_kthread_wakeup(struct vhost_worker *worker)
>+{
>+	wake_up_process(worker->kthread_task);
>+}
>+
> static void vhost_task_do_stop(struct vhost_worker *worker)
> {
> 	return vhost_task_stop(worker->vtsk);
> }
>
>+static void vhost_kthread_do_stop(struct vhost_worker *worker)
>+{
>+	kthread_stop(worker->kthread_task);
>+}
>+
> static int vhost_task_worker_create(struct vhost_worker *worker,
> 				    struct vhost_dev *dev, const char *name)
> {
>@@ -762,6 +772,41 @@ static int vhost_task_worker_create(struct vhost_worker *worker,
> 	return 0;
> }
>
>+static int vhost_kthread_worker_create(struct vhost_worker *worker,
>+				       struct vhost_dev *dev, const char *name)
>+{
>+	struct task_struct *task;
>+	u32 id;
>+	int ret;
>+
>+	task = kthread_create(vhost_run_work_kthread_list, worker, "%s", name);
>+	if (IS_ERR(task))
>+		return PTR_ERR(task);
>+
>+	worker->kthread_task = task;
>+	wake_up_process(task);
>+	ret = xa_alloc(&dev->worker_xa, &id, worker, xa_limit_32b, GFP_KERNEL);
>+	if (ret < 0)
>+		goto stop_worker;
>+
>+	ret = vhost_attach_task_to_cgroups(worker);
>+	if (ret)
>+		goto stop_worker;
>+
>+	worker->id = id;
>+	return 0;
>+
>+stop_worker:
>+	vhost_kthread_do_stop(worker);
>+	return ret;
>+}
>+
>+static const struct vhost_worker_ops kthread_ops = {
>+	.create = vhost_kthread_worker_create,
>+	.stop = vhost_kthread_do_stop,
>+	.wakeup = vhost_kthread_wakeup,
>+};
>+
> static const struct vhost_worker_ops vhost_task_ops = {
> 	.create = vhost_task_worker_create,
> 	.stop = vhost_task_do_stop,
>@@ -773,7 +818,8 @@ static struct vhost_worker *vhost_worker_create(struct vhost_dev *dev)
> 	struct vhost_worker *worker;
> 	char name[TASK_COMM_LEN];
> 	int ret;
>-	const struct vhost_worker_ops *ops = &vhost_task_ops;
>+	const struct vhost_worker_ops *ops =
>+		dev->inherit_owner ? &vhost_task_ops : &kthread_ops;
>
> 	worker = kzalloc(sizeof(*worker), GFP_KERNEL_ACCOUNT);
> 	if (!worker)
>diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
>index 98895e299efa..af4b2f7d3b91 100644
>--- a/drivers/vhost/vhost.h
>+++ b/drivers/vhost/vhost.h
>@@ -37,6 +37,7 @@ struct vhost_worker_ops {
> };
>
> struct vhost_worker {
>+	struct task_struct *kthread_task;
                           ^
nit: I'm not a fan of tabs, but here all the other fields have it, so I 
would put it in.

> 	struct vhost_task	*vtsk;
> 	struct vhost_dev	*dev;
> 	/* Used to serialize device wide flushing with worker swapping. */
>-- 
>2.45.0
>

The patch LGTM:

Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>