i40evf: Use smp_rmb rather than read_barrier_depends

commit f72271e2a0ae4277d53c4053f5eed8bb346ba38a upstream.

The original issue being fixed in this patch was seen with the ixgbe
driver, but the same issue exists with i40evf as well, as the code is
very similar. read_barrier_depends is not sufficient to ensure
loads following it are not speculatively loaded out of order
by the CPU, which can result in stale data being loaded, causing
potential system crashes.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Acked-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
index 04c7c1557a0c770ab0f256d3012cd3b9be70240e..139c8103d83a77aa4fd0aa1b945a17d9adce6c5b 100644 (file)
--- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
@@ -222,7 +222,7 @@ static bool i40e_clean_tx_irq(struct i40e_ring *tx_ring, int budget)
                        break;
 
                /* prevent any other reads prior to eop_desc */
-               read_barrier_depends();
+               smp_rmb();
 
                /* we have caught up to head, no work left to do */
                if (tx_head == tx_desc)