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

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Date:	Tue, 5 May 2015 22:09:31 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Toshi Kani <toshi.kani@...com>
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, 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.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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