RDMA/rxe: Create AH index and return to user space

Make changes to rdma_user_rxe.h to allow indexing AH objects, passing the
index in UD send WRs to the driver and returning the index to the rxe
provider.

Modify rxe_create_ah() to add an index to AH when created and if called
from a new user provider return it to user space. If called from an old
provider mark the AH as not having a useful index.  Modify rxe_destroy_ah
to drop the index before deleting the object.

Link: https://lore.kernel.org/r/20211007204051.10086-4-rpearsonhpe@gmail.com
Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/sw/rxe/rxe_verbs.c

@@ -158,9 +158,19 @@ static int rxe_create_ah(struct ib_ah *ibah,
 			 struct ib_udata *udata)
 
 {
-	int err;
 	struct rxe_dev *rxe = to_rdev(ibah->device);
 	struct rxe_ah *ah = to_rah(ibah);
+	struct rxe_create_ah_resp __user *uresp = NULL;
+	int err;
+
+	if (udata) {
+		/* test if new user provider */
+		if (udata->outlen >= sizeof(*uresp))
+			uresp = udata->outbuf;
+		ah->is_user = true;
+	} else {
+		ah->is_user = false;
+	}
 
 	err = rxe_av_chk_attr(rxe, init_attr->ah_attr);
 	if (err)
@@ -170,6 +180,24 @@ static int rxe_create_ah(struct ib_ah *ibah,
 	if (err)
 		return err;
 
+	/* create index > 0 */
+	rxe_add_index(ah);
+	ah->ah_num = ah->pelem.index;
+
+	if (uresp) {
+		/* only if new user provider */
+		err = copy_to_user(&uresp->ah_num, &ah->ah_num,
+					 sizeof(uresp->ah_num));
+		if (err) {
+			rxe_drop_index(ah);
+			rxe_drop_ref(ah);
+			return -EFAULT;
+		}
+	} else if (ah->is_user) {
+		/* only if old user provider */
+		ah->ah_num = 0;
+	}
+
 	rxe_init_av(init_attr->ah_attr, &ah->av);
 	return 0;
 }
@@ -202,6 +230,7 @@ static int rxe_destroy_ah(struct ib_ah *ibah, u32 flags)
 {
 	struct rxe_ah *ah = to_rah(ibah);
 
+	rxe_drop_index(ah);
 	rxe_drop_ref(ah);
 	return 0;
 }

drivers/infiniband/sw/rxe/rxe_verbs.h

@@ -48,6 +48,8 @@ struct rxe_ah {
 	struct rxe_pool_entry	pelem;
 	struct rxe_pd		*pd;
 	struct rxe_av		av;
+	bool			is_user;
+	int			ah_num;
 };
 
 struct rxe_cqe {

include/uapi/rdma/rdma_user_rxe.h

@@ -99,7 +99,8 @@ struct rxe_send_wr {
 			__u32	remote_qkey;
 			__u16	pkey_index;
 			__u16	reserved;
-			__u32	pad[5];
+			__u32	ah_num;
+			__u32	pad[4];
 			struct rxe_av av;
 		} ud;
 		struct {
@@ -170,6 +171,11 @@ struct rxe_recv_wqe {
 	struct rxe_dma_info	dma;
 };
 
+struct rxe_create_ah_resp {
+	__u32 ah_num;
+	__u32 reserved;
+};
+
 struct rxe_create_cq_resp {
 	struct mminfo mi;
 };