On 05/23/2014 10:52 AM, Brian King wrote:
> 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@xxxxxxxxxxxxxxxxxx>
Acked-by: Nathan Fontenot <nfont@xxxxxxxxxxxxxxxxxx>
> ---
>
> 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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