[PATCH 3.16 111/136] igbvf: Use smp_rmb rather than read_barrier_depends

[Ben Hutchings]

3.16.54-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Brian King <brking@xxxxxxxxxxxxxxxxxx>

commit 1e1f9ca546556e508d021545861f6b5fc75a95fe upstream.

The original issue being fixed in this patch was seen with the ixgbe
driver, but the same issue exists with igbvf 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@xxxxxxxxxxxxxxxxxx>
Acked-by: Jesse Brandeburg <jesse.brandeburg@xxxxxxxxx>
Tested-by: Aaron Brown <aaron.f.brown@xxxxxxxxx>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@xxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/net/ethernet/intel/igbvf/netdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/ethernet/intel/igbvf/netdev.c
+++ b/drivers/net/ethernet/intel/igbvf/netdev.c
@@ -808,7 +808,7 @@ static bool igbvf_clean_tx_irq(struct ig
 			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->wb.status & cpu_to_le32(E1000_TXD_STAT_DD)))