linux-kernel - Re: [RFC net-next 0/6] Cleanup IRQ affinity checks in several drivers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240814080915.005cb9ac@kernel.org>
Date: Wed, 14 Aug 2024 08:09:15 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Joe Damato <jdamato@...tly.com>
Cc: netdev@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>, "David
 S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Harshitha Ramamurthy <hramamurthy@...gle.com>, "moderated list:INTEL
 ETHERNET DRIVERS" <intel-wired-lan@...ts.osuosl.org>, Jeroen de Borst
 <jeroendb@...gle.com>, Jiri Pirko <jiri@...nulli.us>, Leon Romanovsky
 <leon@...nel.org>, open list <linux-kernel@...r.kernel.org>, "open
 list:MELLANOX MLX4 core VPI driver" <linux-rdma@...r.kernel.org>, Lorenzo
 Bianconi <lorenzo@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Praveen
 Kaligineedi <pkaligineedi@...gle.com>, Przemek Kitszel
 <przemyslaw.kitszel@...el.com>, Saeed Mahameed <saeedm@...dia.com>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Shailend Chand
 <shailend@...gle.com>, Tariq Toukan <tariqt@...dia.com>, Tony Nguyen
 <anthony.l.nguyen@...el.com>, Willem de Bruijn <willemb@...gle.com>, Yishai
 Hadas <yishaih@...dia.com>, Ziwei Xiao <ziweixiao@...gle.com>
Subject: Re: [RFC net-next 0/6] Cleanup IRQ affinity checks in several
 drivers

On Wed, 14 Aug 2024 13:12:08 +0100 Joe Damato wrote:
> Actually... how about a slightly different approach, which caches
> the affinity mask in the core?

I was gonna say :)

>   0. Extend napi struct to have a struct cpumask * field
> 
>   1. extend netif_napi_set_irq to:
>     a. store the IRQ number in the napi struct (as you suggested)
>     b. call irq_get_effective_affinity_mask to store the mask in the
>        napi struct
>     c. set up generic affinity_notify.notify and
>        affinity_notify.release callbacks to update the in core mask
>        when it changes

This part I'm not an export on.

>   2. add napi_affinity_no_change which now takes a napi_struct
> 
>   3. cleanup all 5 drivers:
>     a. add calls to netif_napi_set_irq for all 5 (I think no RTNL
>        is needed, so I think this would be straight forward?)
>     b. remove all affinity_mask caching code in 4 of 5 drivers
>     c. update all 5 drivers to call napi_affinity_no_change in poll
> 
> Then ... anyone who adds support for netif_napi_set_irq to their
> driver in the future gets automatic support in-core for
> caching/updating of the mask? And in the future netdev-genl could
> dump the mask since its in-core?
> 
> I'll mess around with that locally to see how it looks, but let me
> know if that sounds like a better overall approach.

Could we even handle this directly as part of __napi_poll(),
once the driver gives core all of the relevant pieces of information ?