netdev - Re: [PATCH bpf-next v4 00/17] AF_XDP infrastructure improvements and mlx5e support

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Date:   Thu, 13 Jun 2019 16:11:23 +0200
From:   Björn Töpel <bjorn.topel@...el.com>
To:     Maxim Mikityanskiy <maximmi@...lanox.com>,
        Björn Töpel <bjorn.topel@...il.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Jonathan Lemon <bsd@...com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Maciej Fijalkowski <maciejromanfijalkowski@...il.com>
Subject: Re: [PATCH bpf-next v4 00/17] AF_XDP infrastructure improvements and
 mlx5e support


On 2019-06-13 16:01, Maxim Mikityanskiy wrote:
> On 2019-06-13 15:58, Björn Töpel wrote:
>> On Wed, 12 Jun 2019 at 22:49, Jakub Kicinski
>> <jakub.kicinski@...ronome.com> wrote:
>>>
>>> On Wed, 12 Jun 2019 15:56:33 +0000, Maxim Mikityanskiy wrote:
>>>> UAPI is not changed, XSK RX queues are exposed to the kernel. The lower
>>>> half of the available amount of RX queues are regular queues, and the
>>>> upper half are XSK RX queues.
>>>
>>> If I have 32 queues enabled on the NIC and I install AF_XDP socket on
>>> queue 10, does the NIC now have 64 RQs, but only first 32 are in the
>>> normal RSS map?
>>>
>>
>> Additional, related, question to Jakub's: Say that I'd like to hijack
>> all 32 Rx queues of the NIC. I create 32 AF_XDP socket and attach them
>> in zero-copy mode to the device. What's the result?
> 
> There are 32 regular RX queues (0..31) and 32 XSK RX queues (32..63). If
> you want 32 zero-copy AF_XDP sockets, you can attach them to queues
> 32..63, and the regular traffic won't be affected at all.
> 
Thanks for getting back! More questions!

Ok, so I cannot (with zero-copy) get the regular traffic into AF_XDP
sockets?

How does qids map? Can I only bind a zero-copy socket to qid 32..63 in
the example above?

Say that I have a a copy-mode AF_XDP socket bound to queue 2. In this
case I will receive the regular traffic from queue 2. Enabling zero-copy
for the same queue, will this give an error, or receive AF_XDP specific
traffic from queue 2+32? Or return an error, and require an explicit
bind to any of the queues 32..63?


Thanks,
Björn