net: Google gve: Remove dma_wmb() before ringing doorbell (b54ef37b) · Commits · 戴 / test

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@oracle.com> Signed-off-by:

Liran Alon <liran.alon@oracle.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

drivers/net/ethernet/google/gve/gve_rx.c

+0 −2

Original line number	Diff line number	Diff line
		@@ -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);
		}

drivers/net/ethernet/google/gve/gve_tx.c

+0 −6

Original line number	Diff line number	Diff line
		@@ -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;
		}

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