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Commit f5832fa2 authored by Brian King's avatar Brian King Committed by James Bottomley
Browse files

[SCSI] ibmvfc: Fix command completion handling 



Commands which are completed by the VIOS are placed on a CRQ
in kernel memory for the ibmvfc driver to process. Each CRQ
entry is 16 bytes. The ibmvfc driver reads the first 8 bytes
to check if the entry is valid, then reads the next 8 bytes to get
the handle, which is a pointer the completed command. This fixes
an issue seen on Power 7 where the processor reordered the
loads from memory, resulting in processing command completion
with a stale handle. This could result in command timeouts,
and also early completion of commands.

Signed-off-by: default avatarBrian King <brking@linux.vnet.ibm.com>
Signed-off-by: default avatarJames Bottomley <James.Bottomley@suse.de>
parent 859e8167

drivers/scsi/ibmvscsi/ibmvfc.c

+6 −0
Original line number Diff line number Diff line
@@ -3013,6 +3013,7 @@ static struct ibmvfc_async_crq *ibmvfc_next_async_crq(struct ibmvfc_host *vhost) 
	if (crq->valid & 0x80) {

		if (++async_crq->cur == async_crq->size)

			async_crq->cur = 0;

		rmb();

	} else

		crq = NULL;
@@ -3035,6 +3036,7 @@ static struct ibmvfc_crq *ibmvfc_next_crq(struct ibmvfc_host *vhost) 
	if (crq->valid & 0x80) {

		if (++queue->cur == queue->size)

			queue->cur = 0;

		rmb();

	} else

		crq = NULL;
@@ -3083,12 +3085,14 @@ static void ibmvfc_tasklet(void *data) 
		while ((async = ibmvfc_next_async_crq(vhost)) != NULL) {

			ibmvfc_handle_async(async, vhost);

			async->valid = 0;

			wmb();

		}



		/* Pull all the valid messages off the CRQ */

		while ((crq = ibmvfc_next_crq(vhost)) != NULL) {

			ibmvfc_handle_crq(crq, vhost);

			crq->valid = 0;

			wmb();

		}



		vio_enable_interrupts(vdev);
@@ -3096,10 +3100,12 @@ static void ibmvfc_tasklet(void *data) 
			vio_disable_interrupts(vdev);

			ibmvfc_handle_async(async, vhost);

			async->valid = 0;

			wmb();

		} else if ((crq = ibmvfc_next_crq(vhost)) != NULL) {

			vio_disable_interrupts(vdev);

			ibmvfc_handle_crq(crq, vhost);

			crq->valid = 0;

			wmb();

		} else

			done = 1;

	}