linux-kernel - Re: [PATCH v5 6/6] mtrr, mm, x86: Enhance MTRR checks for KVA huge page mapping

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Date:	Mon, 18 May 2015 14:21:08 -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, mcgrof@...e.com
Subject: Re: [PATCH v5 6/6] mtrr, mm, x86: Enhance MTRR checks for KVA huge
 page mapping

On Mon, 2015-05-18 at 22:01 +0200, Borislav Petkov wrote:
> On Mon, May 18, 2015 at 01:31:59PM -0600, Toshi Kani wrote:
> > Well, #2 and #3 are independent. That is, uniform can be set regardless
> 
> Not #2 and #3 above - the original #2 and #3 ones. I've written them out
> detailed to show what I mean.

The original #2 and #3 are set independently as well. They do not depend
on each other condition being a specific value.

> > The caller is responsible for verifying the conditions that are safe to
> > create huge page.
> 
> How is the caller ever going to be able to do anything about it?

The caller is the one who makes the condition checks necessary to create
a huge page mapping.  mtrr_type_look() only returns how the given range
is related with MTRRs.

> Regardless, I'd prefer to not duplicate comments and rather put a short
> sentence pointing the reader to the comments over mtrr_type_lookup()
> where this all is being explained in detail.
> 
> I'll fix it up.

I appreciate your help.

Thanks,
-Toshi


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