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

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Message-ID: <1432043228.25898.0.camel@misato.fc.hp.com>
Date:	Tue, 19 May 2015 07:47:08 -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 Tue, 2015-05-19 at 15:23 +0200, Borislav Petkov wrote:
> On Tue, May 19, 2015 at 01:44:37PM +0200, Borislav Petkov wrote:
> > > Try with a smaller page size.
> > > 
> > > The callers, pud_set_huge() and pmd_set_huge(), check if the given range
> > > is safe with MTRRs for creating a huge page mapping.  If not, they fail
> > > the request, which leads their callers, ioremap_pud_range() and
> > > ioremap_pmd_range(), to retry with a smaller page size, i.e. 1GB -> 2MB
> > > -> 4KB.  4KB may not have overlap with MTRRs (hence no checking is
> > > necessary), which will succeed as before.
> 
> Scratch that, I think I have it now. And I even have a good feeling
> about it :-)

Looks good. Thanks for the update!
-Toshi


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