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

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

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.


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

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"


Thanks,
ferruh