RDMA/siw: Fix page address mapping in TX path

Use the correct kmap()/kunmap() flow to determine page address used for
CRC computation. Using page_address() is wrong, since page might be in
highmem.

Fixes: b9be6f18 ("rdma/siw: transmit path")
Link: https://lore.kernel.org/r/20190909132427.30264-1-bmt@zurich.ibm.comReported-by: Krishnamraju Eraparaju <krishna2@chelsio.com>
Signed-off-by: Bernard Metzler <bmt@zurich.ibm.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/sw/siw/siw_qp_tx.c

@@ -520,11 +520,12 @@ static int siw_tx_hdt(struct siw_iwarp_tx *c_tx, struct socket *s)
 							c_tx->mpa_crc_hd,
 							iov[seg].iov_base,
 							plen);
-				} else if (do_crc)
-					crypto_shash_update(
-						c_tx->mpa_crc_hd,
-						page_address(p) + fp_off,
+				} else if (do_crc) {
+					crypto_shash_update(c_tx->mpa_crc_hd,
+							    kmap(p) + fp_off,
 							    plen);
+					kunmap(p);
+				}
 			} else {
 				u64 pa = ((sge->laddr + sge_off) & PAGE_MASK);