[3.13.y.z extended stable] Patch "ibmvscsi: Add memory barriers for send / receive" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    ibmvscsi: Add memory barriers for send / receive

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.6.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From ed19ae9c847a712488400374385c4d1a704dbb26 Mon Sep 17 00:00:00 2001
From: Brian King <brking at linux.vnet.ibm.com>
Date: Fri, 23 May 2014 10:52:11 -0500
Subject: 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 at linux.vnet.ibm.com>
Acked-by: Nathan Fontenot <nfont at linux.vnet.ibm.com>
Signed-off-by: Christoph Hellwig <hch at lst.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/scsi/ibmvscsi/ibmvscsi.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c
index c3d4991..c5bb0e0 100644
--- a/drivers/scsi/ibmvscsi/ibmvscsi.c
+++ b/drivers/scsi/ibmvscsi/ibmvscsi.c
@@ -185,6 +185,11 @@ static struct viosrp_crq *crq_queue_next_crq(struct crq_queue *queue)
 	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 ibmvscsi_host_data *hostdata,
 {
 	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);
 }

--
1.9.1