The vhost now uses vhost_task and workers as a child of the owner thread.
While this aligns with containerization principles, it confuses some
legacy userspace applications, therefore, we are reintroducing kthread
API support.

Introduce a new parameter to enable users to choose between kthread and
task mode.

By default, this parameter is set to true, so the default behavior
remains unchanged by this patch.

Signed-off-by: Cindy Lu <lulu@redhat.com>
---
 drivers/vhost/vhost.c | 1 +
 drivers/vhost/vhost.h | 9 +++++++++
 2 files changed, 10 insertions(+)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 63612faeab72..250dc43f1786 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -552,6 +552,7 @@ void vhost_dev_init(struct vhost_dev *dev,
 	dev->byte_weight = byte_weight;
 	dev->use_worker = use_worker;
 	dev->msg_handler = msg_handler;
+	dev->inherit_owner = true;
 	init_waitqueue_head(&dev->wait);
 	INIT_LIST_HEAD(&dev->read_list);
 	INIT_LIST_HEAD(&dev->pending_list);
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index bb75a292d50c..19bb94922a0e 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -176,6 +176,15 @@ struct vhost_dev {
 	int byte_weight;
 	struct xarray worker_xa;
 	bool use_worker;
+	/*
+	 * If inherit_owner is true we use vhost_tasks to create
+	 * the worker so all settings/limits like cgroups, NPROC,
+	 * scheduler, etc are inherited from the owner. If false,
+	 * we use kthreads and only attach to the same cgroups
+	 * as the owner for compat with older kernels.
+	 * here we use true as default value
+	 */
+	bool inherit_owner;
 	int (*msg_handler)(struct vhost_dev *dev, u32 asid,
 			   struct vhost_iotlb_msg *msg);
 };
-- 
2.45.0

On Mon, Apr 21, 2025 at 10:44:07AM +0800, Cindy Lu wrote:
>The vhost now uses vhost_task and workers as a child of the owner thread.
>While this aligns with containerization principles, it confuses some
>legacy userspace applications, therefore, we are reintroducing kthread
>API support.
>
>Introduce a new parameter to enable users to choose between kthread and
>task mode.
>
>By default, this parameter is set to true, so the default behavior
>remains unchanged by this patch.
>
>Signed-off-by: Cindy Lu <lulu@redhat.com>
>---
> drivers/vhost/vhost.c | 1 +
> drivers/vhost/vhost.h | 9 +++++++++
> 2 files changed, 10 insertions(+)

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

>
>diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>index 63612faeab72..250dc43f1786 100644
>--- a/drivers/vhost/vhost.c
>+++ b/drivers/vhost/vhost.c
>@@ -552,6 +552,7 @@ void vhost_dev_init(struct vhost_dev *dev,
> 	dev->byte_weight = byte_weight;
> 	dev->use_worker = use_worker;
> 	dev->msg_handler = msg_handler;
>+	dev->inherit_owner = true;
> 	init_waitqueue_head(&dev->wait);
> 	INIT_LIST_HEAD(&dev->read_list);
> 	INIT_LIST_HEAD(&dev->pending_list);
>diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
>index bb75a292d50c..19bb94922a0e 100644
>--- a/drivers/vhost/vhost.h
>+++ b/drivers/vhost/vhost.h
>@@ -176,6 +176,15 @@ struct vhost_dev {
> 	int byte_weight;
> 	struct xarray worker_xa;
> 	bool use_worker;
>+	/*
>+	 * If inherit_owner is true we use vhost_tasks to create
>+	 * the worker so all settings/limits like cgroups, NPROC,
>+	 * scheduler, etc are inherited from the owner. If false,
>+	 * we use kthreads and only attach to the same cgroups
>+	 * as the owner for compat with older kernels.
>+	 * here we use true as default value
>+	 */
>+	bool inherit_owner;
> 	int (*msg_handler)(struct vhost_dev *dev, u32 asid,
> 			   struct vhost_iotlb_msg *msg);
> };
>-- 
>2.45.0
>

On Mon, Apr 21, 2025 at 10:45 AM Cindy Lu <lulu@redhat.com> wrote:
>
> The vhost now uses vhost_task and workers as a child of the owner thread.
> While this aligns with containerization principles, it confuses some
> legacy userspace applications, therefore, we are reintroducing kthread
> API support.
>
> Introduce a new parameter to enable users to choose between kthread and
> task mode.
>
> By default, this parameter is set to true, so the default behavior
> remains unchanged by this patch.
>
> Signed-off-by: Cindy Lu <lulu@redhat.com>

Acked-by: Jason Wang <jasowang@redhat.com>

Thanks