ibmvscsi: Add memory barriers for send / receive
commit 7114aae02742d6b5c5a0d39a41deb61d415d3717 upstream.
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 <brking@linux.vnet.ibm.com>
Acked-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c
index 1e29efc..c62b3e5 100644
--- a/drivers/scsi/ibmvscsi/ibmvscsi.c
+++ b/drivers/scsi/ibmvscsi/ibmvscsi.c
@@ -185,6 +185,11 @@
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 @@
{
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);
}