Add a memory barrier prior to sending a new command to the VIOS
to ensure the VIOS does not receive stale data in the command buffer.
Also add a memory barrier when processing the CRQ for completed commands.
Signed-off-by: Brian King <brk...@linux.vnet.ibm.com>
---
drivers/scsi/ibmvscsi/ibmvscsi.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff -puN drivers/scsi/ibmvscsi/ibmvscsi.c~ibmvscsi_barrier
drivers/scsi/ibmvscsi/ibmvscsi.c
--- linux/drivers/scsi/ibmvscsi/ibmvscsi.c~ibmvscsi_barrier 2014-05-23
10:41:35.000000000 -0500
+++ linux-bjking1/drivers/scsi/ibmvscsi/ibmvscsi.c 2014-05-23
10:42:53.000000000 -0500
@@ -185,6 +185,11 @@ static struct viosrp_crq *crq_queue_next
if (crq->valid & 0x80) {
if (++queue->cur == queue->size)
queue->cur = 0;
+
+ /* Ensure the read of the valid bit occurs before reading any
+ * other bits of the CRQ entry
+ */
+ rmb();
} else
crq = NULL;
spin_unlock_irqrestore(&queue->lock, flags);
@@ -203,6 +208,11 @@ static int ibmvscsi_send_crq(struct ibmv
{
struct vio_dev *vdev = to_vio_dev(hostdata->dev);
+ /*
+ * Ensure the command buffer is flushed to memory before handing it
+ * over to the VIOS to prevent it from fetching any stale data.
+ */
+ mb();
return plpar_hcall_norets(H_SEND_CRQ, vdev->unit_address, word1, word2);
}
_
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