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

["Loftus, Ciara" <ciara.loftus@intel.com>]

> 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.

Thanks,
Ciara

>