linux-kernel - Re: [PATCH] genirq: Keep affinity_hint unchanged if it has a value

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: <171eb20e618f8c05ef8169e892a1ed08cf580ee9@linux.dev>
Date: Wed, 12 Mar 2025 03:20:48 +0000
From: "Yajun Deng" <yajun.deng@...ux.dev>
To: "Thomas Gleixner" <tglx@...utronix.de>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH] genirq: Keep affinity_hint unchanged if it has a value

March 11, 2025 at 10:14 PM, "Thomas Gleixner" <tglx@...utronix.de> wrote:



> 
> On Tue, Mar 11 2025 at 09:33, Yajun Deng wrote:
> 
> > 
> > affinity_hint is a hint to user space for preferred irq affinity, but
> > 
> >  it could chang if the value it points to is changed. In other words,
> > 
> >  the hint is invalid.
> > 
> 
> That's a problem of the driver which provides the hint.
> 
> > 
> > For example, if affinity_hint points to smp_affinity, smp_affinity
> > 
> >  is changed by the user, and affinity_hint would chang. affinity_hint
> > 
> >  couldn't as a hint to the user, it should keep the value if it has.
> > 
> 
> What is 'smp_affinity'? 

It's 'desc->irq_common_data.affinity'.
> 
> I really fail to understand the problem you are trying to solve.

irq_update_affinity_hint(irq, desc->irq_common_data.affinity);

As in this code, this means affinity_hint points to smp_affinity.

If someone were to bind several irqs to the same core, affinity_hint would change.

it couldn't as a hint to the user.

This patch allocates memory for affinity_hint and keeps the first value, even if someone

modifies smp_affinity, affinity_hint wouldn't change, it can as a hint to the user.


> 
> Thanks,
> 
>  tglx
>