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

Stefano Garzarella
2025-04-07T08:09:25Z

On Mon, 7 Apr 2025 at 05:14, Cindy Lu <lulu@redhat.com> wrote:
>
> On Tue, Apr 1, 2025 at 9:48 PM Stefano Garzarella <sgarzare@redhat.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@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
> >
> 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
> > >
> >
>