linux-kernel - Re: [PATCH] x86, AMD: Correct F15h IC aliasing issue

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Date:	Thu, 28 Jul 2011 16:13:48 +0200
From:	Borislav Petkov <bp@...64.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Borislav Petkov <bp@...64.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	"Przywara, Andre" <Andre.Przywara@....com>,
	"Pohlack, Martin" <Martin.Pohlack@....com>
Subject: Re: [PATCH] x86, AMD: Correct F15h IC aliasing issue

On Thu, Jul 28, 2011 at 10:02:46AM -0400, H. Peter Anvin wrote:
> On 07/28/2011 06:44 AM, Borislav Petkov wrote:
> > On Wed, Jul 27, 2011 at 01:16:04PM -0400, H. Peter Anvin wrote:
> >>> + * Create a contiguous bitmask starting at bit position @lo and ending at
> >>> + * position @hi. For example
> >>> + *
> >>> + * GENMASK_ULL(21, 39) gives us the 64bit vector 0x000000ffffe00000.
> >>> + */
> >>> +#define _GENMASK_T(cast, type, lo, hi) \
> >>> +       (((cast)(1##type << ((hi) - (lo) + 1)) - 1) << (lo))
> >>> +#define GENMASK(lo, hi)                _GENMASK_T(unsigned, U, lo, hi)
> >>> +#define GENMASK_UL(lo, hi)     _GENMASK_T(unsigned long, UL, lo, hi)
> >>> +#define GENMASK_ULL(lo, hi)    _GENMASK_T(unsigned long long, ULL, lo, hi)
> >>> +
> >>
> >> These really need to be usable from assembly language, too (in which
> >> case you of course need to not have the cast and suffix), so it probably
> >> should be defined in <linux/const.h> with the other constant macros.
> > 
> > How about that:
> > 
> > #define _GENMASK_T(cast, type, lo, hi) \
> > 	        ((_AT(cast, (_AC(1,type) << ((hi) - (lo) + 1))) - 1) << (lo))
> > #define GENMASK(lo, hi)         _GENMASK_T(unsigned, U, lo, hi)
> > #define GENMASK_UL(lo, hi)      _GENMASK_T(unsigned long, UL, lo, hi)
> > #define GENMASK_ULL(lo, hi)     _GENMASK_T(unsigned long long, ULL, lo, hi)
> > 
> > outside of __KERNEL__ scope?
> > 
> 
> Then everything needs another underscore.

You want them to be _GENMASK{,_UL,_ULL}? Why? Because they're "calling"
macros with a single underscore? Actually, I've always wondered on what
our exact rules on underscores are. I can deduce the nesting level of
macros based on number of underscores but what else?

Thanks.

-- 
Regards/Gruss,
Boris.

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