linux-kernel - Re: [PATCH] x86: avoid pointless fields of struct cpuinfo

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Date:	Wed, 27 Apr 2011 18:07:16 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jan Beulich <JBeulich@...ell.com>
CC:	mingo@...e.hu, tglx@...utronix.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: avoid pointless fields of struct cpuinfo_x86

On 04/27/2011 08:07 AM, Jan Beulich wrote:
> Several of the flag fields of this structure are completely unused in
> certain (common) configurations. Don't pointlessly reserve space for
> them, and have truly flag-only fields consume a single bit only.
> 
> Make functionality detection conditional upon (partly new) config
> options that are now also used to control the presence of those
> fields.

If you're going to make them bitflags, please use the features array we
already have.  I do not think there is any point in compressing the
array if we're not doing something epicly wrong.

One thing I would like to see is to move the bug flags into an array
separate from the features array; the bug array should be OR'd together
(if there is a bug on any CPU, it is here) instead of AND'ed; or we
could just put them into the features array with negative logic (the
lack of a bug is a feature.)

That way we get to reuse all of our machinery.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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