[RFC V1 06/13] vhost-vdpa: VHOST_BACKEND_F_IOTLB_REMAP

[Steve Sistare <steven.sistare@oracle.com>]

Add the VHOST_BACKEND_F_IOTLB_REMAP backend capability, which indicates
that VHOST_IOTLB_REMAP is supported.

If VHOST_BACKEND_F_IOTLB_REMAP is advertised, then the user must call
VHOST_IOTLB_REMAP after ownership of a device is transferred to a new
process via VHOST_NEW_OWNER.  Disabling the feature during negotiation
does not negate this requirement.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 drivers/vhost/vdpa.c             | 8 +++++++-
 include/uapi/linux/vhost_types.h | 2 ++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index ec5ca20bd47d..8fe1562d24af 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -789,7 +789,8 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
 				 BIT_ULL(VHOST_BACKEND_F_SUSPEND) |
 				 BIT_ULL(VHOST_BACKEND_F_RESUME) |
 				 BIT_ULL(VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK) |
-				 BIT_ULL(VHOST_BACKEND_F_NEW_OWNER)))
+				 BIT_ULL(VHOST_BACKEND_F_NEW_OWNER) |
+				 BIT_ULL(VHOST_BACKEND_F_IOTLB_REMAP)))
 			return -EOPNOTSUPP;
 		if ((features & BIT_ULL(VHOST_BACKEND_F_SUSPEND)) &&
 		     !vhost_vdpa_can_suspend(v))
@@ -1229,11 +1230,16 @@ static int vhost_vdpa_process_iotlb_remap(struct vhost_vdpa *v,
 	u64 start = msg->iova;
 	u64 last = start + msg->size - 1;
 	struct vhost_iotlb_map *map;
+	u64 features;
 	int r = 0;
 
 	if (msg->perm || !msg->size)
 		return -EINVAL;
 
+	features = ops->get_backend_features(vdpa);
+	if (!(features & BIT_ULL(VHOST_BACKEND_F_IOTLB_REMAP)))
+		return -EOPNOTSUPP;
+
 	map = vhost_iotlb_itree_first(iotlb, start, last);
 	if (!map)
 		return -ENOENT;
diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
index 35908315ff55..7e79e9bd0f7b 100644
--- a/include/uapi/linux/vhost_types.h
+++ b/include/uapi/linux/vhost_types.h
@@ -203,5 +203,7 @@ struct vhost_vdpa_iova_range {
 #define VHOST_BACKEND_F_IOTLB_PERSIST  0x8
 /* Supports VHOST_NEW_OWNER */
 #define VHOST_BACKEND_F_NEW_OWNER  0x9
+/* Supports VHOST_IOTLB_REMAP */
+#define VHOST_BACKEND_F_IOTLB_REMAP  0xa
 
 #endif
-- 
2.39.3