On 11/24/20 11:43 PM, Michael Ellerman wrote:
Thomas Falcon <tlfal...@linux.ibm.com> writes:
Ensure that received Subordinate Command-Response Queue (SCRQ)
entries are properly read in order by the driver. These queues
are used in the ibmvnic device to process RX buffer and TX completion
descriptors. dma_rmb barriers have been added after checking for a
pending descriptor to ensure the correct descriptor entry is checked
and after reading the SCRQ descriptor to ensure the entire
descriptor is read before processing.
Fixes: 032c5e828 ("Driver for IBM System i/p VNIC protocol")
Signed-off-by: Thomas Falcon <tlfal...@linux.ibm.com>
---
drivers/net/ethernet/ibm/ibmvnic.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/net/ethernet/ibm/ibmvnic.c
b/drivers/net/ethernet/ibm/ibmvnic.c
index 2aa40b2..489ed5e 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -2403,6 +2403,8 @@ static int ibmvnic_poll(struct napi_struct *napi, int
budget)
if (!pending_scrq(adapter, adapter->rx_scrq[scrq_num]))
break;
+ /* ensure that we do not prematurely exit the polling loop */
+ dma_rmb();
I'd be happier if these comments were more specific about which read(s)
they are ordering vs which other read(s).
I'm sure it's obvious to you, but it may not be to a future author,
and/or after the code has been refactored over time.
Thank you for reviewing! I will submit a v2 soon with clearer comments
on the reads being ordered here.
Thanks,
Tom
next = ibmvnic_next_scrq(adapter, adapter->rx_scrq[scrq_num]);
rx_buff =
(struct ibmvnic_rx_buff *)be64_to_cpu(next->
@@ -3098,6 +3100,9 @@ static int ibmvnic_complete_tx(struct ibmvnic_adapter
*adapter,
unsigned int pool = scrq->pool_index;
int num_entries = 0;
+ /* ensure that the correct descriptor entry is read */
+ dma_rmb();
+
next = ibmvnic_next_scrq(adapter, scrq);
for (i = 0; i < next->tx_comp.num_comps; i++) {
if (next->tx_comp.rcs[i]) {
@@ -3498,6 +3503,9 @@ static union sub_crq *ibmvnic_next_scrq(struct
ibmvnic_adapter *adapter,
}
spin_unlock_irqrestore(&scrq->lock, flags);
+ /* ensure that the entire SCRQ descriptor is read */
+ dma_rmb();
+
return entry;
}
cheers
