This patch reintroduces kthread mode support in vhost,
It also introduces struct vhost_worker_ops to abstract
worker create/stop/wakeup operations.
* Bring back the original vhost_worker() implementation,
and renamed to vhost_run_work_kthread_list().
* Add cgroup support for the kthread
* Introduce struct vhost_worker_ops:
- Encapsulates create / stop / wake‑up callbacks.
- vhost_worker_create() selects the proper ops according to
inherit_owner.
This partially reverts or improves upon:
commit 6e890c5d5021 ("vhost: use vhost_tasks for worker threads")
commit 1cdaafa1b8b4 ("vhost: replace single worker pointer with xarray")
Signed-off-by: Cindy Lu <l...@redhat.com>
---
drivers/vhost/vhost.c | 188 ++++++++++++++++++++++++++++++++++++++----
drivers/vhost/vhost.h | 12 +++
2 files changed, 182 insertions(+), 18 deletions(-)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 250dc43f1786..be97028a8baf 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -22,6 +22,7 @@
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/kthread.h>
+#include <linux/cgroup.h>
#include <linux/module.h>
#include <linux/sort.h>
#include <linux/sched/mm.h>
@@ -242,7 +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);
}
}
@@ -388,6 +389,44 @@ static void vhost_vq_reset(struct vhost_dev *dev,
__vhost_vq_meta_reset(vq);
}
+static int vhost_run_work_kthread_list(void *data)
+{
+ struct vhost_worker *worker = data;
+ struct vhost_work *work, *work_next;
+ struct vhost_dev *dev = worker->dev;
+ struct llist_node *node;
+
+ kthread_use_mm(dev->mm);
+
+ for (;;) {
+ /* mb paired w/ kthread_stop */
+ set_current_state(TASK_INTERRUPTIBLE);
+
+ if (kthread_should_stop()) {
+ __set_current_state(TASK_RUNNING);
+ break;
+ }
+ node = llist_del_all(&worker->work_list);
+ if (!node)
+ schedule();
+
+ node = llist_reverse_order(node);
+ /* make sure flag is seen after deletion */
+ smp_wmb();
+ llist_for_each_entry_safe(work, work_next, node, node) {
+ clear_bit(VHOST_WORK_QUEUED, &work->flags);
+ __set_current_state(TASK_RUNNING);
+ kcov_remote_start_common(worker->kcov_handle);
+ work->fn(work);
+ kcov_remote_stop();
+ cond_resched();
+ }
+ }
+ kthread_unuse_mm(dev->mm);
+
+ return 0;
+}
+
static bool vhost_run_work_list(void *data)
{
struct vhost_worker *worker = data;
@@ -582,6 +621,46 @@ long vhost_dev_check_owner(struct vhost_dev *dev)
}
EXPORT_SYMBOL_GPL(vhost_dev_check_owner);
+struct vhost_attach_cgroups_struct {
+ struct vhost_work work;
+ struct task_struct *owner;
+ int ret;
+};
+
+static void vhost_attach_cgroups_work(struct vhost_work *work)
+{
+ struct vhost_attach_cgroups_struct *s;
+
+ s = container_of(work, struct vhost_attach_cgroups_struct, work);
+ s->ret = cgroup_attach_task_all(s->owner, current);
+}
+
+static int vhost_attach_task_to_cgroups(struct vhost_worker *worker)
+{
+ struct vhost_attach_cgroups_struct attach;
+ int saved_cnt;
+
+ attach.owner = current;
+
+ vhost_work_init(&attach.work, vhost_attach_cgroups_work);
+ vhost_worker_queue(worker, &attach.work);
+
+ mutex_lock(&worker->mutex);
+
+ /*
+ * Bypass attachment_cnt check in __vhost_worker_flush:
+ * Temporarily change it to INT_MAX to bypass the check
+ */
+ saved_cnt = worker->attachment_cnt;
+ worker->attachment_cnt = INT_MAX;
+ __vhost_worker_flush(worker);
+ worker->attachment_cnt = saved_cnt;
+
+ mutex_unlock(&worker->mutex);
+
+ return attach.ret;
+}
+
/* Caller should have device mutex */
bool vhost_dev_has_owner(struct vhost_dev *dev)
{
@@ -627,7 +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);
}
@@ -650,42 +729,115 @@ 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_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)
+{
+ 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;
+ }
+ worker->id = id;
+ 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,
+ .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 =
+ dev->inherit_owner ? &vhost_task_ops : &kthread_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..af4b2f7d3b91 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -26,7 +26,18 @@ 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 task_struct *kthread_task;
struct vhost_task *vtsk;
struct vhost_dev *dev;
/* Used to serialize device wide flushing with worker swapping. */
@@ -36,6 +47,7 @@ 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
