[PATCH 4.9 25/72] scsi: lpfc: Add missing memory barrier

From: Greg Kroah-Hartman
Date: Sun Nov 19 2017 - 10:08:00 EST

4.9-stable review patch. If anyone has any objections, please let me know.


From: James Smart <james.smart@xxxxxxxxxxxx>

[ Upstream commit 6b3b3bdb83b4ad51252d21bb13596db879e51850 ]

On loosely ordered memory systems (PPC for example), the WQE elements
were being updated in memory, but not necessarily flushed before the
separate doorbell was written to hw which would cause hw to dma the
WQE element. Thus, the hardware occasionally received partially
updated WQE data.

Add the memory barrier after updating the WQE memory.

Signed-off-by: Dick Kennedy <dick.kennedy@xxxxxxxxxxxx>
Signed-off-by: James Smart <james.smart@xxxxxxxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
drivers/scsi/lpfc/lpfc_sli.c | 2 ++
1 file changed, 2 insertions(+)

--- a/drivers/scsi/lpfc/lpfc_sli.c
+++ b/drivers/scsi/lpfc/lpfc_sli.c
@@ -119,6 +119,8 @@ lpfc_sli4_wq_put(struct lpfc_queue *q, u
if (q->phba->sli3_options & LPFC_SLI4_PHWQ_ENABLED)
bf_set(wqe_wqid, &wqe->generic.wqe_com, q->queue_id);
lpfc_sli_pcimem_bcopy(wqe, temp_wqe, q->entry_size);
+ /* ensure WQE bcopy flushed before doorbell write */
+ wmb();

/* Update the host index before invoking device */
host_index = q->host_index;