From: Liran Alon <liran.alon@xxxxxxxxxx> [ Upstream commit b54ef37b1ce892fdf6b632d566246d2f2f539910 ] Current code use dma_wmb() to ensure Rx/Tx descriptors are visible to device before writing to doorbell. However, these dma_wmb() are wrong and unnecessary. Therefore, they should be removed. iowrite32be() called from gve_rx_write_doorbell()/gve_tx_put_doorbell() should guaratee that all previous writes to WB/UC memory is visible to device before the write done by iowrite32be(). E.g. On ARM64, iowrite32be() calls __iowmb() which expands to dma_wmb() and only then calls __raw_writel(). Reviewed-by: Si-Wei Liu <si-wei.liu@xxxxxxxxxx> Signed-off-by: Liran Alon <liran.alon@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/net/ethernet/google/gve/gve_rx.c | 2 -- drivers/net/ethernet/google/gve/gve_tx.c | 6 ------ 2 files changed, 8 deletions(-) diff --git a/drivers/net/ethernet/google/gve/gve_rx.c b/drivers/net/ethernet/google/gve/gve_rx.c index edec61dfc8687..9f52e72ff641d 100644 --- a/drivers/net/ethernet/google/gve/gve_rx.c +++ b/drivers/net/ethernet/google/gve/gve_rx.c @@ -418,8 +418,6 @@ bool gve_clean_rx_done(struct gve_rx_ring *rx, int budget, rx->cnt = cnt; rx->fill_cnt += work_done; - /* restock desc ring slots */ - dma_wmb(); /* Ensure descs are visible before ringing doorbell */ gve_rx_write_doorbell(priv, rx); return gve_rx_work_pending(rx); } diff --git a/drivers/net/ethernet/google/gve/gve_tx.c b/drivers/net/ethernet/google/gve/gve_tx.c index f4889431f9b70..d0244feb03011 100644 --- a/drivers/net/ethernet/google/gve/gve_tx.c +++ b/drivers/net/ethernet/google/gve/gve_tx.c @@ -487,10 +487,6 @@ netdev_tx_t gve_tx(struct sk_buff *skb, struct net_device *dev) * may have added descriptors without ringing the doorbell. */ - /* Ensure tx descs from a prior gve_tx are visible before - * ringing doorbell. - */ - dma_wmb(); gve_tx_put_doorbell(priv, tx->q_resources, tx->req); return NETDEV_TX_BUSY; } @@ -505,8 +501,6 @@ netdev_tx_t gve_tx(struct sk_buff *skb, struct net_device *dev) if (!netif_xmit_stopped(tx->netdev_txq) && netdev_xmit_more()) return NETDEV_TX_OK; - /* Ensure tx descs are visible before ringing doorbell */ - dma_wmb(); gve_tx_put_doorbell(priv, tx->q_resources, tx->req); return NETDEV_TX_OK; } -- 2.20.1
