linux-kernel - Re: [PATCH v4 2/7] mtrr, x86: Fix MTRR lookup to handle inclusive entry

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Date:	Tue, 05 May 2015 14:06:48 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	akpm@...ux-foundation.org, hpa@...or.com, tglx@...utronix.de,
	mingo@...hat.com, linux-mm@...ck.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, dave.hansen@...el.com,
	Elliott@...com, pebolle@...cali.nl
Subject: Re: [PATCH v4 2/7] mtrr, x86: Fix MTRR lookup to handle inclusive
 entry

On Tue, 2015-05-05 at 22:09 +0200, Borislav Petkov wrote:
> On Tue, May 05, 2015 at 01:31:32PM -0600, Toshi Kani wrote:
> > Well, the comment kinda says it already, but I will try to clarify it.
> > 
> >            /*
> >             * We have start:end spanning across an MTRR.
> >             * We split the region into either
> >             * - start_state:1
> >             *     (start:mtrr_end) (mtrr_end:end)
> >             * - end_state:1 or inclusive:1
> >             *     (start:mtrr_start) (mtrr_start:end)
> 
> What I mean is this:
> 
> 		* - start_state:1
> 		*     (start:mtrr_end) (mtrr_end:end)
> 		* - end_state:1
> 		*     (start:mtrr_start) (mtrr_start:end)
> 		* - inclusive:1
> 		*     (start:mtrr_start) (mtrr_start:mtrr_end) (mtrr_end:end)
> 		*
> 		* depending on kind of overlap.
> 		*
> 		* Return the type of the first region and a pointer to the start
> 		* of next region so that caller will be advised to lookup again
> 		* after having adjusted start and end.
> 		*
> 		* Note: This way we handle multiple overlaps as well.
> 		*/
> 
> We add comments so that people can read them and can quickly understand
> what the function does. Not to make them parse it and wonder why
> inclusive:1 is listed together with end_state:1 which returns two
> intervals.
> 
> Note that I changed the text to talk about the *next* region and not
> about the *second* region, to make it even more clear.

Thanks for the suggestion.  I see your point.  I will update it
accordingly.
-Toshi



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