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

Cindy Lu
2025-03-28T10:05:04Z

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