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Message-ID: <CAGxU2F5mCHdByvcuj8SOiXCj+MtD5=GM4yEprpeiDU8ZZAVsLw@mail.gmail.com>
Date: Mon, 7 Apr 2025 10:09:11 +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 Mon, 7 Apr 2025 at 05:14, Cindy Lu <lulu@...hat.com> wrote:
>
> On Tue, Apr 1, 2025 at 9:48 PM Stefano Garzarella <sgarzare@...hat.com> wrote:
> >
> > 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
> >
> Thanks a lot Stefano. I previously tried moving xa_alloc() out, but
> that made the code strange.
> I think keeping xa_alloc() in the create_ops function completes the
> job in  a single function, and maybe it could be used in some other
> functions in the future

Sure, if you tried, and it doesn't add benefits, that's perfectly fine
to ignore this suggestion! ;-)

Thanks,
Stefano

> thanks
> cindy
>
> > >+      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
> > >
> >
>


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