On Fri, 2016-09-09 at 14:29 -0700, John Fastabend wrote: > From: Alexei Starovoitov <a...@fb.com> >
So it looks like e1000_xmit_raw_frame() can return early, say if there is no available descriptor. > +static void e1000_xmit_raw_frame(struct e1000_rx_buffer *rx_buffer_info, > + unsigned int len, > + struct net_device *netdev, > + struct e1000_adapter *adapter) > +{ > + struct netdev_queue *txq = netdev_get_tx_queue(netdev, 0); > + struct e1000_hw *hw = &adapter->hw; > + struct e1000_tx_ring *tx_ring; > + > + if (len > E1000_MAX_DATA_PER_TXD) > + return; > + > + /* e1000 only support a single txq at the moment so the queue is being > + * shared with stack. To support this requires locking to ensure the > + * stack and XDP are not running at the same time. Devices with > + * multiple queues should allocate a separate queue space. > + */ > + HARD_TX_LOCK(netdev, txq, smp_processor_id()); > + > + tx_ring = adapter->tx_ring; > + > + if (E1000_DESC_UNUSED(tx_ring) < 2) { > + HARD_TX_UNLOCK(netdev, txq); > + return; > + } > + > + e1000_tx_map_rxpage(tx_ring, rx_buffer_info, len); > + e1000_tx_queue(adapter, tx_ring, 0/*tx_flags*/, 1); > + > + writel(tx_ring->next_to_use, hw->hw_addr + tx_ring->tdt); > + mmiowb(); > + > + HARD_TX_UNLOCK(netdev, txq); > +} > + > #define NUM_REGS 38 /* 1 based count */ > static void e1000_regdump(struct e1000_adapter *adapter) > { > @@ -4142,6 +4247,19 @@ static struct sk_buff *e1000_alloc_rx_skb(struct > e1000_adapter *adapter, > return skb; > } > + act = e1000_call_bpf(prog, page_address(p), length); > + switch (act) { > + case XDP_PASS: > + break; > + case XDP_TX: > + dma_sync_single_for_device(&pdev->dev, > + dma, > + length, > + DMA_TO_DEVICE); > + e1000_xmit_raw_frame(buffer_info, length, > + netdev, adapter); > + buffer_info->rxbuf.page = NULL; So I am trying to understand how pages are not leaked ?