linux-kernel - Re: [PATCH v4 RESEND 4/11] x86/asm: Fix pud/pmd interfaces to handle large PAT bit

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Date:	Mon, 9 Nov 2015 22:10:55 +0200
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Toshi Kani <toshi.kani@....com>
Cc:	Boris Ostrovsky <boris.ostrovsky@...cle.com>, hpa@...or.com,
	tglx@...utronix.de, mingo@...hat.com, akpm@...ux-foundation.org,
	bp@...en8.de, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	x86@...nel.org, jgross@...e.com, konrad.wilk@...cle.com,
	elliott@....com
Subject: Re: [PATCH v4 RESEND 4/11] x86/asm: Fix pud/pmd interfaces to handle
 large PAT bit

On Mon, Nov 09, 2015 at 12:16:41PM -0700, Toshi Kani wrote:
> On Mon, 2015-11-09 at 13:06 -0500, Boris Ostrovsky wrote:
> > On 09/17/2015 02:24 PM, Toshi Kani wrote:
> > > Now that we have pud/pmd mask interfaces, which handle pfn & flags
> > > mask properly for the large PAT bit.
> > > 
> > > Fix pud/pmd pfn & flags interfaces by replacing PTE_PFN_MASK and
> > > PTE_FLAGS_MASK with the pud/pmd mask interfaces.
> > > 
> > > Suggested-by: Juergen Gross <jgross@...e.com>
> > > Signed-off-by: Toshi Kani <toshi.kani@....com>
> > > Cc: Juergen Gross <jgross@...e.com>
> > > Cc: Konrad Wilk <konrad.wilk@...cle.com>
> > > Cc: Thomas Gleixner <tglx@...utronix.de>
> > > Cc: H. Peter Anvin <hpa@...or.com>
> > > Cc: Ingo Molnar <mingo@...hat.com>
> > > Cc: Borislav Petkov <bp@...en8.de>
> > > ---
> > >   arch/x86/include/asm/pgtable.h       |   14 ++++++++------
> > >   arch/x86/include/asm/pgtable_types.h |    4 ++--
> > >   2 files changed, 10 insertions(+), 8 deletions(-)
> > > 
> > 
> > 
> > Looks like this commit is causing this splat for 32-bit kernels. I am 
> > attaching my config file, just in case.
> 
> Thanks for the report!  I'd like to reproduce the issue since I am not sure how
> this change caused it...
> 
> I tried to build a kernel with the attached config file, and got the following
> error.  Not sure what I am missing.  

The problem is that PMD_PAGE_MASK as well as PUD_PAGE_MASK are 'unsigned
long', not 'unsigned long long'. So on 32-bit with PAE enabled your
pmd_pfn_mask()/pud_pfn_mask() will truncate bits 32..43 of pmd/pudval and
you'll never get proper page frame for pages above 4G.

-- 
 Kirill A. Shutemov
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