[v8] vhost: Add support of kthread API

[PATCH v8 5/8] vhost: Reintroduce kthread mode support in vhost

Posted by Cindy Lu 8 months, 3 weeks ago

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
commit 6e890c5d5021 ("vhost: use vhost_tasks for worker threads")

Signed-off-by: Cindy Lu <lulu@redhat.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;
 	struct vhost_task	*vtsk;
 	struct vhost_dev	*dev;
 	/* Used to serialize device wide flushing with worker swapping. */
-- 
2.45.0

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

Posted by Mike Christie 8 months, 2 weeks ago

On 3/28/25 5:02 AM, Cindy Lu wrote:
> +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)

If you go to stop_worker here, it will leave the worker in the xa above. I
think you need another goto to unwind that.

> +		goto stop_worker;
> +
> +	worker->id = id;
> +	return 0;
> +
> +stop_worker:
> +	vhost_kthread_do_stop(worker);
> +	return ret;
> +}
> +

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

Posted by Cindy Lu 8 months, 2 weeks ago

On Tue, Apr 8, 2025 at 12:04 AM Mike Christie
<michael.christie@oracle.com> wrote:
>
> On 3/28/25 5:02 AM, Cindy Lu wrote:
> > +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)
>
> If you go to stop_worker here, it will leave the worker in the xa above. I
> think you need another goto to unwind that.
>
sure, will fix this
Thanks
Cindy
> > +             goto stop_worker;
> > +
> > +     worker->id = id;
> > +     return 0;
> > +
> > +stop_worker:
> > +     vhost_kthread_do_stop(worker);
> > +     return ret;
> > +}
> > +
>

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

Posted by Stefano Garzarella 8 months, 3 weeks ago

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@redhat.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@redhat.com>

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

Posted by Cindy Lu 8 months, 2 weeks ago

On Tue, Apr 1, 2025 at 9:51 PM Stefano Garzarella <sgarzare@redhat.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@redhat.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@redhat.com>
>