lpfc: Add iotag memory barrier

Add a memory barrier to ensure the valid bit is read before
any of the cqe payload is read. This fixes an issue seen
on Power where the cqe payload was getting loaded before
the valid bit. When this occurred, we saw an iotag out of
range error when a command completed, but since the iotag
looked invalid the command didn't get completed to scsi core.
Later we hit the command timeout, attempted to abort the command,
then waited for the aborted command to get returned. Since the
adapter already returned the command, we timeout waiting,
and end up escalating EEH all the way to host reset. This
patch fixes this issue.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/scsi/lpfc/lpfc_sli.c b/drivers/scsi/lpfc/lpfc_sli.c
index 572579f87de4fb..d82dcb74be121f 100644
--- a/drivers/scsi/lpfc/lpfc_sli.c
+++ b/drivers/scsi/lpfc/lpfc_sli.c
@@ -263,6 +263,7 @@ lpfc_sli4_eq_get(struct lpfc_queue *q)
 		return NULL;
 
 	q->hba_index = idx;
+	mb();
 	return eqe;
 }
 
@@ -368,6 +369,7 @@ lpfc_sli4_cq_get(struct lpfc_queue *q)
 
 	cqe = q->qe[q->hba_index].cqe;
 	q->hba_index = idx;
+	mb();
 	return cqe;
 }