Re: [PATCH v4] net/af_xdp: re-enable secondary process support

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 2/11/2022 7:28 AM, Loftus, Ciara wrote:
>>
>> On 2/10/2022 5:47 PM, Loftus, Ciara wrote:
>>>> Subject: Re: [PATCH v4] net/af_xdp: re-enable secondary process support
>>>>
>>>> On 2/10/2022 3:40 PM, Loftus, Ciara wrote:
>>>>>> Subject: Re: [PATCH v4] net/af_xdp: re-enable secondary process
>> support
>>>>>>
>>>>>> On 2/9/2022 9:48 AM, Ciara Loftus wrote:
>>>>>>> Secondary process support had been disabled for the AF_XDP PMD
>>>>>> because
>>>>>>> there was no logic in place to share the AF_XDP socket file descriptors
>>>>>>> between the processes. This commit introduces this logic using the
>> IPC
>>>>>>> APIs.
>>>>>>>
>>>>>>> Rx and Tx are disabled in the secondary process due to memory
>> mapping
>>>> of
>>>>>>> the AF_XDP rings being assigned by the kernel in the primary process
>>>> only.
>>>>>>> However other operations including retrieval of stats are permitted.
>>>>>>>
>>>>>>> Signed-off-by: Ciara Loftus <ciara.loftus@intel.com>
>>>>>>>
>>>>>>
>>>>>> Hi Ciara,
>>>>>>
>>>>>> When I tried to test the patch getting following error [1], it doesn't look
>>>>>> related to this patch but can you help to fix the issue, thanks.
>>>>>>
>>>>>> [1]
>>>>>> libxdp: Couldn't find a BPF file with name xsk_def_xdp_prog.o
>>>>>> xsk_configure(): Failed to create xsk socket.
>>>>>> eth_rx_queue_setup(): Failed to configure xdp socket
>>>>>> Fail to configure port 2 rx queues
>>>>>> EAL: Error - exiting with code: 1
>>>>>
>>>>>
>>>>> Hi Ferruh,
>>>>>
>>>>> This file should be generated when libxdp is compiled.
>>>>> Mine is located @ /usr/local/lib/bpf/xsk_def_xdp_prog.o
>>>>> Can you check if that file is there for you? It could be in
>>>> /usr/local/lib64/bpf/ on your machine.
>>>>> What kernel are you running on?
>>>>>
>>>>
>>>> It is in: /usr/local/lib64/bpf/xsk_def_xdp_prog.o
>>>>
>>>> I had to compile libxdp from source because OS package version was old
>>>> to work with af_xdp.
>>>> Is something required to point location of this file to af_xdp PMD?
>>>>
>>>> I run kernel:
>>>> 5.15.16-200.fc35.x86_64
>>>
>>> I read through the libxdp code to figure out what happens when searching
>> for the file:
>>> https://github.com/xdp-project/xdp-
>> tools/blob/v1.2.2/lib/libxdp/libxdp.c#L1055
>>>
>>> secure_getenv(XDP_OBJECT_ENVVAR) is called which according to the
>> README "defaults to /usr/lib/bpf (or /usr/lib64/bpf on systems using a split
>> library path)".
>>> If that fails, BPF_OBJECT_PATH will be searched, which points to
>> /usr/lib/bpf
>>>
>>> I discovered that on my system the getenv() call fails, but the file is
>> eventually found because luckily BPF_OBJECT_PATH points to the
>> appropriate place for me (lib):
>>> https://github.com/xdp-project/xdp-tools/blob/v1.2.2/lib/util/util.h#L24
>>> I suspect the same failure is happening for you, but since
>> BPF_OBJECT_PATH points to lib and not lib64, the file is not found.
>>> As a temporary measure can you create a symlink in /usr/local/lib/bpf/ to
>> point to /usr/local/lib/bpf/xsk_def_xdp_prog.o
>>> I will investigate the libxdp issue further. Maybe a change is needed in the
>> library. If a change or setup recommendation is needed in DPDK I will create a
>> patch.
>>>
>>
>>
>> I don't have XDP_OBJECT_ENVVAR or BPF_OBJECT_PATH environment
>> variables set,
>> if they should be we should document them.
>>
>> When I created '/usr/local/lib/bpf/' link, the BPF file found.
>> This should be clarified/documented for users.
> 
> Ok. Ideally we shouldn't have to create the symlink. I will look for a better solution and submit a patch.
> The symlink might be a temporary solution if another solution is not found.
> 

ack

>>
>>
>> And still observing following two:
>>
>> 1) I don't know what following log means:
>> Configuring Port 2 (socket 0)
>> libbpf: elf: skipping unrecognized data section(7) .xdp_run_config
>> libbpf: elf: skipping unrecognized data section(8) xdp_metadata
>> libxdp: XDP flag not supported by libxdp.
>> libbpf: elf: skipping unrecognized data section(8) xdp_metadata
>> libbpf: elf: skipping unrecognized data section(8) xdp_metadata
> 
> I reported this and a patch was submitted to libbpf to demote those logs:
> https://www.spinics.net/lists/bpf/msg49140.html
> It looks like the patch never made it. I'll chase it up.

thanks

> Anyway, the logs can be ignored as they are not errors.
> 

Should we document this?

>>
>> 2) When I try to create two af_xdp interface, I only got one:
>> "--vdev net_af_xdp,iface=enp24s0f1 --vdev net_af_xdp,iface=enp24s0f0"
> 
> This is also expected as you haven't given each vdev a unique name. Try:
> "--vdev net_af_xdp0,iface=enp24s0f1 --vdev net_af_xdp1,iface=enp24s0f0"
> 

Yes of course :(, it works now, and I did verify the proc-info stats works.

> Thank you for the testing.
> 
> Ciara
> 
>>
>>
>> Thanks,
>> ferruh