linux-kernel - Re: [git pull] x86 fixes

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Message-ID: <20080327205527.GA21912@elte.hu>
Date:	Thu, 27 Mar 2008 21:55:27 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Harvey Harrison <harvey.harrison@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [git pull] x86 fixes


* Harvey Harrison <harvey.harrison@...il.com> wrote:

> -#ifdef CONFIG_X86_32
>  	/* Catch an obscure case of prefetch inside an NX page: */
> -	if ((__supported_pte_mask & _PAGE_NX) && (error_code & 16))
> -		return 0;
> -#endif
> -
> -	/* If it was a exec fault on NX page, ignore */
> -	if (error_code & PF_INSTR)
> +	if ((__supported_pte_mask & _PAGE_NX) && (error_code & PF_INSTR))
>  		return 0;

heh, did the exact same cleanup :)

i suspect we would be fine with a simple:

	if (error_code & PF_INSTR)
  		return 0;

because if we get a fault on an instruction fetch then it clearly cannot 
be a prefetch erratum ... The NX condition simply comes from a cautious 
32-bit workaround. (on 64-bit we always have NX - at least on AMD which 
has this erratum.)

and thus the currently pulled code is not incorrect, just ugly and 
nonsensical.

	Ingo
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