[PATCH] RDMA/irdma: always route IB_WR_REG_MR through the allocated PBL

[Stefan Metzmacher <metze@samba.org>]

irdma_alloc_mr() always allocates a PBL via irdma_get_pble(), but
irdma_post_send()'s IB_WR_REG_MR handling only pointed the FAST_REGISTER
WQE at that PBL (chunk_size != 0, first_pm_pbl_index) when
iwmr->npages exceeded IRDMA_MIN_PAGES_PER_FMR (1) - leaving chunk_size
at 0 for a single-page (npages == 1) registration, telling hardware to
use direct/PBL-less addressing for a registration that was never
allocated that way.

This reproduces as data corruption / an IOMMU IO_PAGE_FAULT when a
peer later performs an RDMA WRITE/READ against such a single-page
FRWR-registered MR, even though ib_map_mr_sg() itself reports success.
100% reproducible on iWARP, intermittent on RoCEv2, with fs/smb/smbdirect's
own single-page memory registrations on an Intel E810-CQDA2 (irdma).

Intel's current out-of-tree irdma driver (2.6.96) never gates this on
npages - it always sets chunk_size/first_pm_pbl_index based on the
actual PBL level (PBLE_LEVEL_1 vs PBLE_LEVEL_2), matching what
irdma_alloc_mr() actually allocated. Mirror that here instead of the
npages-based heuristic.

Also drop the reg_addr_pa assignment. irdma_sc_mr_fast_register()
packs reg_addr_pa into the FAST_REGISTER WQE's PBLADDR field, which
hardware only consults when chunk_size == 0 (direct/PBL-less
addressing); with chunk_size now always nonzero for this opcode, that
field is never read for IB_WR_REG_MR and the assignment is dead code -
Intel's driver never sets it for this path either (only the separate,
non-FRWR irdma_sc_mr_reg_non_shared() path actually branches on
chunk_size between reg_addr_pa and first_pm_pbl_index). Removing it is
not required for correctness: *palloc->level1.addr is always a
page-aligned address (low 12 bits zero), so it could never have
collided with the first_pm_pbl_index bits sharing those same bit
positions in the WQE word even if some path still read it.

This leaves one deliberate difference from irdma-2.6.96: that driver also
ties local_fence to the WR's IB_SEND_FENCE flag
(stag_info.local_fence = ib_wr->send_flags & IB_SEND_FENCE) rather than
hardcoding it true for IB_WR_REG_MR. That is a separate, non-corruption
behavioural change, so local_fence is left at true here.

I've tested the change with an Intel-E810-CQDA2 card, lspci show is as:
Intel Corporation Ethernet Controller E810-C for QSFP (rev 02)

Fixes: b48c24c2d710 ("RDMA/irdma: Implement device supported verb APIs")
Cc: Tatyana Nikolova <tatyana.e.nikolova@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Mustafa Ismail <mustafa.ismail@intel.com>
Cc: Shiraz Saleem <shiraz.saleem@intel.com>
Cc: linux-rdma@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Assisted-by: Claude:claude-sonnet-5-5
Tested-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
---
 drivers/infiniband/hw/irdma/verbs.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/infiniband/hw/irdma/verbs.c b/drivers/infiniband/hw/irdma/verbs.c
index 5d71300da0ff..a524e8fc7738 100644
--- a/drivers/infiniband/hw/irdma/verbs.c
+++ b/drivers/infiniband/hw/irdma/verbs.c
@@ -4279,11 +4279,14 @@ static int irdma_post_send(struct ib_qp *ibqp,
 			stag_info.addr_type = IRDMA_ADDR_TYPE_VA_BASED;
 			stag_info.va = (void *)(uintptr_t)iwmr->ibmr.iova;
 			stag_info.total_len = iwmr->ibmr.length;
-			stag_info.reg_addr_pa = *palloc->level1.addr;
-			stag_info.first_pm_pbl_index = palloc->level1.idx;
-			stag_info.local_fence = true;
-			if (iwmr->npages > IRDMA_MIN_PAGES_PER_FMR)
+			if (palloc->level == PBLE_LEVEL_2) {
+				stag_info.chunk_size = 3;
+				stag_info.first_pm_pbl_index = palloc->level2.root.idx;
+			} else {
 				stag_info.chunk_size = 1;
+				stag_info.first_pm_pbl_index = palloc->level1.idx;
+			}
+			stag_info.local_fence = true;
 			err = irdma_sc_mr_fast_register(&iwqp->sc_qp, &stag_info,
 							true);
 			break;
-- 
2.43.0