4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Niklas Cassel niklas.cassel@axis.com
[ Upstream commit a6b25da5e7ba212af5826a662e6a035a79bffabd ]
According to Documentation/memory-barriers.txt, we need to use a dma_rmb() after reading the status/own bit, to ensure that all descriptor fields are read after reading the own bit.
This way, we ensure that the DMA engine is done with the DMA descriptor before we read the other descriptor fields, e.g. reading the tx hardware timestamp (if PTP is enabled).
Signed-off-by: Niklas Cassel niklas.cassel@axis.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c @@ -1343,6 +1343,11 @@ static void stmmac_tx_clean(struct stmma if (unlikely(status & tx_dma_own)) break;
+ /* Make sure descriptor fields are read after reading + * the own bit. + */ + dma_rmb(); + /* Just consider the last segment and ...*/ if (likely(!(status & tx_not_ls))) { /* ... verify the status error condition */