[PATCH v8 1/8] vhost: Add a new parameter in vhost_dev to allow user select kthread

Cindy Lu
2025-03-28T10:04:21Z

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 app, Therefore, we are reintroducing kthread API support.

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

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