linux-kernel - Re: [PATCH net-next v6 3/3] selftests: drv-net: Test queue xsk attribute

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Message-ID: <Z6usZlrFJShn67su@mini-arch>
Date: Tue, 11 Feb 2025 12:00:38 -0800
From: Stanislav Fomichev <stfomichev@...il.com>
To: Joe Damato <jdamato@...tly.com>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, horms@...nel.org, kuba@...nel.org,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Shuah Khan <shuah@...nel.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	open list <linux-kernel@...r.kernel.org>,
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>,
	"open list:XDP (eXpress Data Path):Keyword:(?:b|_)xdp(?:b|_)" <bpf@...r.kernel.org>
Subject: Re: [PATCH net-next v6 3/3] selftests: drv-net: Test queue xsk
 attribute

On 02/11, Joe Damato wrote:
> On Tue, Feb 11, 2025 at 09:45:56AM -0800, Joe Damato wrote:
> > On Tue, Feb 11, 2025 at 12:09:50PM +0100, Paolo Abeni wrote:
> > > On 2/10/25 8:38 PM, Joe Damato wrote:
> > > > +def check_xdp(cfg, nl, xdp_queue_id=0) -> None:
> > > > +    test_dir = os.path.dirname(os.path.realpath(__file__))
> > > > +    xdp = subprocess.Popen([f"{test_dir}/xdp_helper", f"{cfg.ifindex}", f"{xdp_queue_id}"],
> > > > +                           stdin=subprocess.PIPE, stdout=subprocess.PIPE, bufsize=1,
> > > > +                           text=True)
> > > > +    defer(xdp.kill)
> > > > +
> > > > +    stdout, stderr = xdp.communicate(timeout=10)
> > > > +    rx = tx = False
> > > > +
> > > > +    queues = nl.queue_get({'ifindex': cfg.ifindex}, dump=True)
> > > > +    if not queues:
> > > > +        raise KsftSkipEx("Netlink reports no queues")
> > > > +
> > > > +    for q in queues:
> > > > +        if q['id'] == 0:
> > > > +            if q['type'] == 'rx':
> > > > +                rx = True
> > > > +            if q['type'] == 'tx':
> > > > +                tx = True
> > > > +
> > > > +            ksft_eq(q['xsk'], {})
> > > > +        else:
> > > > +            if 'xsk' in q:
> > > > +                _fail("Check failed: xsk attribute set.")
> > > > +
> > > > +    ksft_eq(rx, True)
> > > > +    ksft_eq(tx, True)
> > > 
> > > This causes self-test failures:
> > > 
> > > https://netdev-3.bots.linux.dev/vmksft-net-drv/results/987742/4-queues-py/stdout
> > > 
> > > but I really haven't done any real investigation here.
> > 
> > I think it's because the test kernel in this case has
> > CONFIG_XDP_SOCKETS undefined [1].
> > 
> > The error printed in the link you mentioned:
> > 
> >   socket creation failed: Address family not supported by protocol
> > 
> > is coming from the C program, which fails to create the AF_XDP
> > socket.
> > 
> > I think the immediate reaction is to add more error checking to the
> > python to make sure that the subprocess succeeded and if it failed,
> > skip.
> > 
> > But, we may want it to fail for other error states instead of
> > skipping? Not sure if there's general guidance on this, but my plan
> > was to have the AF_XDP socket creation failure return a different
> > error code (I dunno maybe -1?) and only skip the test in that case.
> > 
> > Will that work or is there a better way? I only want to skip if
> > AF_XDP doesn't exist in the test kernel.
> > 
> > [1]: https://netdev-3.bots.linux.dev/vmksft-net-drv/results/987742/config
> 
> I'll give it a few more hours incase anyone has comments before I
> resend, but I got something working (tested on kernels with and
> without XDP sockets).
> 
> xdp_helper returns -1 if (errno == EAFNOSUPPORT). All other error
> cases return 1.
> 
> Updated the python to do this:
> 
>   if xdp.returncode == 255:
>       raise KsftSkipEx('AF_XDP unsupported')
>   elif xdp.returncode > 0:
>       raise KsftFailEx('unable to create AF_XDP socket')
> 
> Which seems to work on both types of kernels?
> 
> Happy to take feedback; will hold off on respinning for a bit just
> incase there's a better way I don't know about.

Any reason not to enable CONFIG_XDP_SOCKETS on NIPA kernels? Seems a bit
surprising that we run networking tests without XSKs enabled.