Re: [PATCH net-next v4] xen networking: add basic XDP support for xen-netfront

[Denis Kirjanov <kda@linux-powerpc.org>]

On 3/16/20, Jesper Dangaard Brouer <brouer@redhat.com> wrote:
> On Mon, 16 Mar 2020 16:09:36 +0300
> Denis Kirjanov <kda@linux-powerpc.org> wrote:
>
>> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
>> index 482c6c8..c06ae57 100644
>> --- a/drivers/net/xen-netfront.c
>> +++ b/drivers/net/xen-netfront.c
> [...]
>> @@ -778,6 +790,52 @@ static int xennet_get_extras(struct netfront_queue
>> *queue,
>>  	return err;
>>  }
>>
>> +u32 xennet_run_xdp(struct netfront_queue *queue, struct page *pdata,
>> +		   struct xen_netif_rx_response *rx, struct bpf_prog *prog,
>> +		   struct xdp_buff *xdp)
>> +{
>> +	struct xdp_frame *xdpf;
>> +	u32 len = rx->status;
>> +	u32 act = XDP_PASS;
>> +	int err;
>> +
>> +	xdp->data_hard_start = page_address(pdata);
>> +	xdp->data = xdp->data_hard_start + XDP_PACKET_HEADROOM;
>> +	xdp_set_data_meta_invalid(xdp);
>> +	xdp->data_end = xdp->data + len;
>> +	xdp->rxq = &queue->xdp_rxq;
>> +	xdp->handle = 0;
>> +
>> +	act = bpf_prog_run_xdp(prog, xdp);
>> +	switch (act) {
>> +	case XDP_TX:
>> +		xdpf = convert_to_xdp_frame(xdp);
>> +		err = xennet_xdp_xmit(queue->info->netdev, 1,
>> +				&xdpf, 0);
>
> Strange line wrap, I don't think this is needed, please fix.
>
>
>> +		if (unlikely(err < 0))
>> +			trace_xdp_exception(queue->info->netdev, prog, act);
>> +		break;
>> +	case XDP_REDIRECT:
>> +		err = xdp_do_redirect(queue->info->netdev, xdp, prog);
>
> What is the frame size of the packet memory?

It's XEN_PAGE_SIZE (4k)

>
>
>> +		if (unlikely(err))
>> +			trace_xdp_exception(queue->info->netdev, prog, act);
>> +		xdp_do_flush();
>> +		break;
>> +	case XDP_PASS:
>> +	case XDP_DROP:
>> +		break;
>> +
>> +	case XDP_ABORTED:
>> +		trace_xdp_exception(queue->info->netdev, prog, act);
>> +		break;
>> +
>> +	default:
>> +		bpf_warn_invalid_xdp_action(act);
>> +	}
>> +
>> +	return act;
>> +}
>> +
>
> --
> Best regards,
>   Jesper Dangaard Brouer
>   MSc.CS, Principal Kernel Engineer at Red Hat
>   LinkedIn: http://www.linkedin.com/in/brouer
>
>