[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: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>
diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c
index c2eea71..9372169 100644
--- a/drivers/scsi/ibmvscsi/ibmvfc.c
+++ b/drivers/scsi/ibmvscsi/ibmvfc.c
@@ -3013,6 +3013,7 @@
if (crq->valid & 0x80) {
if (++async_crq->cur == async_crq->size)
async_crq->cur = 0;
+ rmb();
} else
crq = NULL;
@@ -3035,6 +3036,7 @@
if (crq->valid & 0x80) {
if (++queue->cur == queue->size)
queue->cur = 0;
+ rmb();
} else
crq = NULL;
@@ -3083,12 +3085,14 @@
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 @@
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;
}