[PATCH for-next] RDMA/rxe: fix regression caused by recent patch

[Bob Pearson <rpearsonhpe@gmail.com>]

The commit referenced below performs additional checking on
devices used for DMA. Specifically it checks that

device->dma_mask != NULL

Rdma_rxe uses this device when pinning MR memory but did not
set the value of dma_mask. In fact rdma_rxe does not perform
any DMA operations so the value is never used but is checked.

This patch gives dma_mask a valid value. Without this patch
rdma_rxe does not function at all.

Fixes: f959dcd6ddfd2 ("dma-direct: Fix potential NULL pointer dereference")
Signed-off-by: Bob Pearson <rpearson@hpe.com>
---
 drivers/infiniband/sw/rxe/rxe_verbs.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c
index 7652d53af2c1..116a234e92db 100644
--- a/drivers/infiniband/sw/rxe/rxe_verbs.c
+++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
@@ -1134,8 +1134,15 @@ int rxe_register_device(struct rxe_dev *rxe, const char *ibdev_name)
 	dev->node_type = RDMA_NODE_IB_CA;
 	dev->phys_port_cnt = 1;
 	dev->num_comp_vectors = num_possible_cpus();
+
+	/* rdma_rxe never does real DMA but does rely on
+	 * pinning user memory in MRs to avoid page faults
+	 * in responder and completer tasklets
+	 */
 	dev->dev.parent = rxe_dma_device(rxe);
+	dev->dev.dma_mask = DMA_BIT_MASK(64);
 	dev->local_dma_lkey = 0;
+
 	addrconf_addr_eui48((unsigned char *)&dev->node_guid,
 			    rxe->ndev->dev_addr);
 	dev->dev.dma_parms = &rxe->dma_parms;
-- 
2.27.0