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Subject[PATCH 3.11 065/128] ibmvscsi: Add memory barriers for send / receive
Date
3.11.10.14 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Brian King <brking@linux.vnet.ibm.com>

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: Luis Henriques <luis.henriques@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 1e29efc8271a..c62b3e5d44bd 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


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