linux-kernel - Re: [PATCH 01/21] x86: add methods for writing of an MSR on several CPUs

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Message-ID: <49FF24F8.5050008@zytor.com>
Date:	Mon, 04 May 2009 10:25:12 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <borislav.petkov@....com>
CC:	akpm@...ux-foundation.org, greg@...ah.com, mingo@...e.hu,
	tglx@...utronix.de, dougthompson@...ssion.com,
	linux-kernel@...r.kernel.org,
	Mauro Carvalho Chehab <mchehab@...hat.com>
Subject: Re: [PATCH 01/21] x86: add methods for writing of an MSR on	several
 CPUs

Borislav Petkov wrote:
>>
>> Please, for the love of God, no!
>>
>> Make it an array of u64s or (equivalently!) an array of (l,h)
>> structures, not separate arrays for the halves of the register.
> 
> how about something like the following then? If there's agreement I could
> convert all users to struct msr later.
> 

I personally would prefer if you just used an array of u64s.  The whole
l/h split for MSRs was a mistake in the first place.  However, if not,
at least make it a union; using something like:

union msr {
	u32 l[2];
	u64 q;
};

Or fancier, using gcc's anonymous structs/unions:

struct msr {
	union {
		struct {
			u32 l, h;
		};
		u64 q;
	};
};

	-hpa

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

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