| From | Ben Hutchings <> | Date | Mon, 04 Aug 2014 17:48:31 +0100 | Subject | [PATCH 3.2 13/94] ibmvscsi: Add memory barriers for send / receive |
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3.2.62-rc1 review patch. If anyone has any objections, please let me know.
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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> [bwh: Backported to 3.2: as the iSeries code is still present, these functions have different names and live in rpa_vscsi.c.] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- drivers/scsi/ibmvscsi/ibmvscsi.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
--- a/drivers/scsi/ibmvscsi/rpa_vscsi.c +++ b/drivers/scsi/ibmvscsi/rpa_vscsi.c @@ -104,6 +104,11 @@ 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); @@ -122,6 +127,11 @@ static int rpavscsi_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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