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

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Message-ID: <CACLfguWAMYBU4rFtFbjhLkL9P0jvN7w1ZU4-r630kS3GZBaqMg@mail.gmail.com>
Date: Mon, 7 Apr 2025 11:14:29 +0800
From: Cindy Lu <lulu@...hat.com>
To: Stefano Garzarella <sgarzare@...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 Tue, Apr 1, 2025 at 9:51 PM Stefano Garzarella <sgarzare@...hat.com> wrote:
>
> 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.
>
Sure,will fix this
Thanks
Cindy
> >       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>
>