linux-kernel - Re: [PATCH 01/10] Add driver auto probing for x86 features

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Message-ID: <4EE26E8F.9010000@linux.intel.com>
Date:	Fri, 09 Dec 2011 12:24:47 -0800
From:	Andi Kleen <ak@...ux.intel.com>
To:	Jean Delvare <khali@...ux-fr.org>
CC:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	kay.sievers@...y.org, trenn@...e.de, davej@...hat.com,
	axboe@...nel.dk, hpa@...or.com, herbert@...dor.apana.org.au,
	ying.huang@...el.com, lenb@...nel.org
Subject: Re: [PATCH 01/10] Add driver auto probing for x86 features


> Can you guarantee that there is no asymmetric system already working
> today?

I used to have an asymmetric system myself, but we generally subset the 
CPU feature
flags to be the same everywhere and I didn't change any per CPU stepping 
checks
as they were there.

>   If you can't, then your approach could cause a regression. This
> is why I am asking for an API change to let drivers pass a specific CPU
> to x86_match_cpu(). There are at least two drivers who would take
> benefit of this. Your patch set is supposed to only add driver
> auto-loading, and while cleaning up the code in the process is nice, I
> think you should avoid driver behavior changes, these are out of scope
> for such a patch set.

I undoed that change to the coretemp driver and there's no other AFAIK.
Generally most drivers only check the boot cpu.

-Andi
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