linux-kernel - Re: [PATCH net-next RFC] selftests: net: add netpoll basic functionality test

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Message-ID: <aFUeT8HSPYiDyALB@gmail.com>
Date: Fri, 20 Jun 2025 01:39:43 -0700
From: Breno Leitao <leitao@...ian.org>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Willem de Bruijn <willemdebruijn.kernel@...il.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, linux-kselftest@...r.kernel.org,
	ast@...nel.org
Subject: Re: [PATCH net-next RFC] selftests: net: add netpoll basic
 functionality test

On Fri, Jun 13, 2025 at 05:42:33PM -0700, Jakub Kicinski wrote:
> On Fri, 13 Jun 2025 05:47:50 -0700 Breno Leitao wrote:
> > > Or is there another way that the packets could be observed, e.g.,
> > > counters.  
> > 
> > Unfortunately netpoll doesn't expose any data, thus, it is hard to get
> > it. 
> > 
> > I have plans to create a configfs for netpoll, so, we can check for
> > these numbers (as also configure some pre-defined values today, such as
> > USEC_PER_POLL, MAX_SKBS, ip6h->version = 6; ip6h->priority = 0, etc.
> > 
> > In fact, I've an private PoC for this, but, I am modernizing the code
> > first, and creating some selftests to help me with those changes later
> > (given we have very little test on netpoll, and I aim to improve this,
> > given how critical it is for some datacenter designs).
> 
> FWIW you can steal bpftrace integration from this series:
> https://lore.kernel.org/all/20250421222827.283737-22-kuba@kernel.org/

Yes, that would be great. I think we can iterate until we hit the poll
path, otherwise we skip the test at timeout. Something as:

	while (true):
		send msg
		if netpoll_poll_dev() was invoked:
			ksft_exit
		
		if timeout:
			raise KsftSkipEx
	
As soon as your code lands, I will adapt the test to do so. Meanwhile,
I will send the v1 for the netpoll, and later we can iterate.

Thanks for working on this bfptrace helper. This will be useful on other
usecases as well.

--breno