Re: [PATCH net-next v5 13/15] virtio-net: support AF_XDP zc rx

From: Jason Wang <jasowang@redhat.com>
To: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Cc: "Song Liu" <songliubraving@fb.com>,
	"Martin KaFai Lau" <kafai@fb.com>,
	"Jesper Dangaard Brouer" <hawk@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	"Yonghong Song" <yhs@fb.com>,
	"John Fastabend" <john.fastabend@gmail.com>,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Andrew Melnychenko" <andrew@daynix.com>,
	"Andrii Nakryiko" <andrii@kernel.org>,
	netdev@vger.kernel.org,
	"yuri Benditovich" <yuri.benditovich@daynix.com>,
	"Björn Töpel" <bjorn@kernel.org>,
	"dust.li" <dust.li@linux.alibaba.com>,
	"Jonathan Lemon" <jonathan.lemon@gmail.com>,
	"KP Singh" <kpsingh@kernel.org>,
	"Jakub Kicinski" <kuba@kernel.org>,
	bpf@vger.kernel.org, virtualization@lists.linux-foundation.org,
	"David S. Miller" <davem@davemloft.net>,
	"Magnus Karlsson" <magnus.karlsson@intel.com>
Subject: Re: [PATCH net-next v5 13/15] virtio-net: support AF_XDP zc rx
Date: Thu, 17 Jun 2021 14:58:36 +0800	[thread overview]
Message-ID: <a8f79a9d-1328-f5e8-167b-4eda844c52ca@redhat.com> (raw)
In-Reply-To: <1623911825.4660118-1-xuanzhuo@linux.alibaba.com>

在 2021/6/17 下午2:37, Xuan Zhuo 写道:
> On Thu, 17 Jun 2021 14:03:29 +0800, Jason Wang <jasowang@redhat.com> wrote:
>> 在 2021/6/17 下午1:53, Xuan Zhuo 写道:
>>> On Thu, 17 Jun 2021 11:23:52 +0800, Jason Wang <jasowang@redhat.com> wrote:
>>>> 在 2021/6/10 下午4:22, Xuan Zhuo 写道:
>>>>> Compared to the case of xsk tx, the case of xsk zc rx is more
>>>>> complicated.
>>>>>
>>>>> When we process the buf received by vq, we may encounter ordinary
>>>>> buffers, or xsk buffers. What makes the situation more complicated is
>>>>> that in the case of mergeable, when num_buffer > 1, we may still
>>>>> encounter the case where xsk buffer is mixed with ordinary buffer.
>>>>>
>>>>> Another thing that makes the situation more complicated is that when we
>>>>> get an xsk buffer from vq, the xsk bound to this xsk buffer may have
>>>>> been unbound.
>>>>>
>>>>> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
>>>> This is somehow similar to the case of tx where we don't have per vq reset.
>>>>
>>>> [...]
>>>>
>>>>> -	if (vi->mergeable_rx_bufs)
>>>>> +	if (is_xsk_ctx(ctx))
>>>>> +		skb = receive_xsk(dev, vi, rq, buf, len, xdp_xmit, stats);
>>>>> +	else if (vi->mergeable_rx_bufs)
>>>>>     		skb = receive_mergeable(dev, vi, rq, buf, ctx, len, xdp_xmit,
>>>>>     					stats);
>>>>>     	else if (vi->big_packets)
>>>>> @@ -1175,6 +1296,14 @@ static bool try_fill_recv(struct virtnet_info *vi, struct receive_queue *rq,
>>>>>     	int err;
>>>>>     	bool oom;
>>>>>
>>>>> +	/* Because virtio-net does not yet support flow direct,
>>>> Note that this is not the case any more. RSS has been supported by
>>>> virtio spec and qemu/vhost/tap now. We just need some work on the
>>>> virtio-net driver part (e.g the ethool interface).
>>> Oh, are there any plans? Who is doing this work, can I help?
>>
>> Qemu and spec has support RSS.
>>
>> TAP support is ready via steering eBPF program, you can try to play it
>> with current qemu master.
>>
>> The only thing missed is the Linux driver, I think Yuri or Andrew is
>> working on this.
> I feel that in the case of xsk, the flow director is more appropriate.
>
> Users may still want to allocate packets to a certain channel based on
> information such as port/ip/tcp/udp, and then xsk will process them.
>
> I will try to push the flow director to the spec.

That would be fine. For the backend implementation, it could still be 
implemented via steering eBPF.

Thanks

>
> Thanks.
>
>> Thanks
>>
>>
>>> Thanks.
>>>
>>>> Thanks
>>>>
>>>>

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