[PATCH v2 7/7] vhost: Add new UAPI to support change to task mode

[Cindy Lu]

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

Signed-off-by: Cindy Lu <l...@redhat.com>
---
 drivers/vhost/vhost.c      | 18 +++++++++++++++++-
 include/uapi/linux/vhost.h |  2 ++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 08c9e77916ca..0e5c81026acd 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2341,8 +2341,24 @@ 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 inherit_owner;
+
+       if (ioctl == VHOST_SET_INHERIT_FROM_OWNER) {
+               /* Is there an owner already? */
+               if (vhost_dev_has_owner(d)) {
+                       r = -EBUSY;
+                       goto done;
+               }
+               if (copy_from_user(&inherit_owner, argp,
+                                  sizeof(inherit_owner))) {
+                       r = -EFAULT;
+                       goto done;
+               }
+               enforce_inherit_owner = inherit_owner;
+               goto done;
+       }
 
        /* If you are not the owner, you can become one */
        if (ioctl == VHOST_SET_OWNER) {
diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index b95dd84eef2d..1e192038633d 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_INHERIT_FROM_OWNER _IOW(VHOST_VIRTIO, 0x83, bool)
 #endif
-- 
2.45.0