[PATCH v1 7/7] vhost: Add new UAPI to support change to task mode

[Cindy Lu <lulu@redhat.com>]

Add a new UAPI to support setting the vhost device to
use task mode. The user space application needs to use
VHOST_SET_ENFORCE_TASK to set the mode. This setting must
be set before VHOST_SET_OWNER is set.

Signed-off-by: Cindy Lu <lulu@redhat.com>
---
 drivers/vhost/vhost.c      | 16 +++++++++++++++-
 include/uapi/linux/vhost.h |  2 ++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index bf1e971cb06f..8ed6b3a947a9 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2340,14 +2340,28 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
 {
 	struct eventfd_ctx *ctx;
 	u64 p;
-	long r;
+	long r = 0;
 	int i, fd;
+	bool enforce_task;
 
 	/* If you are not the owner, you can become one */
 	if (ioctl == VHOST_SET_OWNER) {
 		r = vhost_dev_set_owner(d);
 		goto done;
 	}
+	if (ioctl == VHOST_SET_ENFORCE_TASK) {
+		/* Is there an owner already? */
+		if (vhost_dev_has_owner(d)) {
+			r = -EBUSY;
+			goto done;
+		}
+		if (copy_from_user(&kthread, argp, sizeof(enforce_task))) {
+			r = -EFAULT;
+			goto done;
+		}
+		use_kthread = enforce_task;
+		goto done;
+	}
 
 	/* You must be the owner to do anything else */
 	r = vhost_dev_check_owner(d);
diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index b95dd84eef2d..9853d62d2d34 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h
@@ -235,4 +235,6 @@
  */
 #define VHOST_VDPA_GET_VRING_SIZE	_IOWR(VHOST_VIRTIO, 0x82,	\
 					      struct vhost_vring_state)
+
+#define VHOST_SET_ENFORCE_TASK _IOW(VHOST_VIRTIO, 0x83, bool)
 #endif
-- 
2.45.0