On 6/22/20, Jesper Dangaard Brouer <bro...@redhat.com> wrote:
>
> On Mon, 22 Jun 2020 12:21:11 +0300 Denis Kirjanov <k...@linux-powerpc.org>
> wrote:
>
>> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
>> index 482c6c8..1b9f49e 100644
>> --- a/drivers/net/xen-netfront.c
>> +++ b/drivers/net/xen-netfront.c
> [...]
>> @@ -560,6 +572,65 @@ static u16 xennet_select_queue(struct net_device
>> *dev, struct sk_buff *skb,
>> return queue_idx;
>> }
>>
>> +static int xennet_xdp_xmit_one(struct net_device *dev, struct xdp_frame
>> *xdpf)
>> +{
>> + struct netfront_info *np = netdev_priv(dev);
>> + struct netfront_stats *tx_stats = this_cpu_ptr(np->tx_stats);
>> + unsigned int num_queues = dev->real_num_tx_queues;
>> + struct netfront_queue *queue = NULL;
>> + struct xen_netif_tx_request *tx;
>> + unsigned long flags;
>> + int notify;
>> +
>> + queue = &np->queues[smp_processor_id() % num_queues];
>> +
>> + spin_lock_irqsave(&queue->tx_lock, flags);
>
> Why are you taking a lock per packet (xdp_frame)?
Hi Jesper,
We have to protect shared ring indices.
>
>> +
>> + tx = xennet_make_first_txreq(queue, NULL,
>> + virt_to_page(xdpf->data),
>> + offset_in_page(xdpf->data),
>> + xdpf->len);
>> +
>> + RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&queue->tx, notify);
>> + if (notify)
>> + notify_remote_via_irq(queue->tx_irq);
>> +
>> + u64_stats_update_begin(&tx_stats->syncp);
>> + tx_stats->bytes += xdpf->len;
>> + tx_stats->packets++;
>> + u64_stats_update_end(&tx_stats->syncp);
>> +
>> + xennet_tx_buf_gc(queue);
>> +
>> + spin_unlock_irqrestore(&queue->tx_lock, flags);
>
> Is the irqsave/irqrestore variant really needed here?
netpoll also invokes the tx completion handler.
>
>> + return 0;
>> +}
>> +
>> +static int xennet_xdp_xmit(struct net_device *dev, int n,
>> + struct xdp_frame **frames, u32 flags)
>> +{
>> + int drops = 0;
>> + int i, err;
>> +
>> + if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
>> + return -EINVAL;
>> +
>> + for (i = 0; i < n; i++) {
>> + struct xdp_frame *xdpf = frames[i];
>> +
>> + if (!xdpf)
>> + continue;
>> + err = xennet_xdp_xmit_one(dev, xdpf);
>> + if (err) {
>> + xdp_return_frame_rx_napi(xdpf);
>> + drops++;
>> + }
>> + }
>> +
>> + return n - drops;
>> +}
>
>
>
> --
> Best regards,
> Jesper Dangaard Brouer
> MSc.CS, Principal Kernel Engineer at Red Hat
> LinkedIn: http://www.linkedin.com/in/brouer
>
>
