linux-kernel - Re: [PATCH] x86, cpu: Fix X86_FEATURE

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Message-ID: <4CAA4C2B.2050909@zytor.com>
Date:	Mon, 04 Oct 2010 14:50:35 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86, cpu: Fix X86_FEATURE_NOPL

>>
>> Agreed that this should be cleaned up.  However, in the meantime I'd
>> like to keep Borislav's patch in the tree since it makes the code
>> technically correct at least.
> 
> I think the cleanup should be easy: on 64-bit unconditionally return
> p6_nops in find_nop_table() since every 64-bit processor should support
> them and on 32-bit never return p6_nops since X86_FEATURE_NOPL is not
> set there and fall back to intel_nops on non-AMD. Which means we can get
> rid of X86_FEATURE_NOPL altogether. Too radical?
> 

This is fine with me, but you may want to check with your employer if
the Intel NOPs will perform slower than the 66 ... 90 NOPs on AMD
processors.

	-hpa
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