netdev - Re: [PATCH net-next] selftests: drv-net: ncdevmem: make configure

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Message-ID: <CAHS8izPa8=2=u6AcrUKEOecuQSOAmwcsXKXAXtdE9tdAJhVGoA@mail.gmail.com>
Date: Mon, 18 Aug 2025 12:53:40 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com, 
	pabeni@...hat.com, andrew+netdev@...n.ch, horms@...nel.org, shuah@...nel.org, 
	sdf@...ichev.me, joe@...a.to, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net-next] selftests: drv-net: ncdevmem: make
 configure_channels() support combined channels

On Fri, Aug 15, 2025 at 4:15 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> ncdevmem tests that the kernel correctly rejects attempts
> to deactivate queues with MPs bound.
>
> Make the configure_channels() test support combined channels.
> Currently it tries to set the queue counts to rx N tx N-1,
> which only makes sense for devices which have IRQs per ring
> type. Most modern devices used combined IRQs/channels with
> both Rx and Tx queues. Since the math is total Rx == combined+Rx
> setting Rx when combined is non-zero will be increasing the total
> queue count, not decreasing as the test intends.
>
> Note that the test would previously also try to set the Tx
> ring count to Rx - 1, for some reason. Which would be 0
> if the device has only 2 queues configured.
>

Yes, I think that was a mistake. I can't think of any reason we'd
really want to do that.

> With this change (device with 2 queues):
>   setting channel count rx:1 tx:1
>   YNL set channels: Kernel error: 'requested channel counts are too low for existing memory provider setting (2)'
>
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>

Reviewed-by: Mina Almasry <almasrymina@...gle.com>

--
Thanks,
Mina