[PATCH 4.4 57/96] fm10k: Use smp_rmb rather than read_barrier_depends

Greg Kroah-Hartman
2017-11-28T10:30:44Z

From: Brian King <brking@linux.vnet.ibm.com>

commit 7b8edcc685b5e2c3c37aa13dc50a88e84a5bfef8 upstream.

The original issue being fixed in this patch was seen with the ixgbe
driver, but the same issue exists with fm10k 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>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/net/ethernet/intel/fm10k/fm10k_main.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/ethernet/intel/fm10k/fm10k_main.c
+++ b/drivers/net/ethernet/intel/fm10k/fm10k_main.c
@@ -1226,7 +1226,7 @@ static bool fm10k_clean_tx_irq(struct fm
break;

/* prevent any other reads prior to eop_desc */
- read_barrier_depends();
+ smp_rmb();

/* if DD is not set pending work has not been completed */
if (!(eop_desc->flags & FM10K_TXD_FLAG_DONE))