linux-kernel - Re: [RFC net 0/1] Fix netdevim to correctly mark NAPI IDs

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Message-ID: <Z_613wmrKRu4R-IP@LQ3V64L9R2>
Date: Tue, 15 Apr 2025 12:39:11 -0700
From: Joe Damato <jdamato@...tly.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>, David Wei <dw@...idwei.uk>,
	Eric Dumazet <edumazet@...gle.com>,
	open list <linux-kernel@...r.kernel.org>,
	Paolo Abeni <pabeni@...hat.com>
Subject: Re: [RFC net 0/1] Fix netdevim to correctly mark NAPI IDs

On Mon, Mar 31, 2025 at 04:39:17PM -0700, Jakub Kicinski wrote:
> On Mon, 31 Mar 2025 15:32:09 -0700 Joe Damato wrote:
> > > Would it be possible / make sense to convert the test to Python
> > > and move it to drivers/net ?  
> > 
> > Hmm. We could; I think originally the busy_poller.c test was added
> > because it was requested by Paolo for IRQ suspension and netdevsim
> > was the only option that I could find that supported NAPI IDs at the
> > time.
> > 
> > busy_poller.c itself seems more like a selftests/net thing since
> > it's testing some functionality of the core networking code.
> 
> I guess in my mind busy polling is tied to having IRQ-capable device.
> Even if bulk of the logic resides in the core.
> 
> > Maybe mixing the napi_id != 0 test into busy_poller.c is the wrong
> > way to go at a higher level. Maybe there should be a test for
> > netdevsim itself that checks napi_id != 0 and that test would make
> > more sense under drivers/net vs mixing a check into busy_poller.c?
> 
> Up to you. The patch make me wonder how many other corner cases / bugs
> we may be missing in drivers. And therefore if we shouldn't flesh out
> more device-related tests. But exercising the core code makes sense
> in itself so no strong feelings.

Sorry to revive this old thread, but I have a bit of time to get
this fixed now. I have a patch for netdevsim but am trying to figure
out what the best way to write a test for this is.

Locally, I've hacked up a tools/testing/selftests/drivers/net/napi_id.py

I'm using NetDrvEpEnv, but am not sure: is there an easy way in
Python to run stuff in a network namespace? Is there an example I
can look at?

In my Python code, I was thinking that I'd call fork and have each
python process (client and server) set their network namespace
according to the NetDrvEpEnv cfg... but wasn't sure if there was a
better/easier way ?

It looks like tools/testing/selftests/net/rds/test.py uses
LoadLibrary to call setns before creating a socket.

Should I go in that direction too?