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

["Loftus, Ciara" <ciara.loftus@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.

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.

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

> 
> 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"

Thank you for the testing.

Ciara

> 
> 
> Thanks,
> ferruh