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, 09 Nov 2015 16:18:54 -0700
From:	Toshi Kani <toshi.kani@....com>
To:	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	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, 2015-11-09 at 17:36 -0500, Boris Ostrovsky wrote:
> On 11/09/2015 03:47 PM, Kirill A. Shutemov wrote:
> > On Mon, Nov 09, 2015 at 02:39:31PM -0500, Boris Ostrovsky wrote:
> > > On 11/09/2015 02:16 PM, 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.
> > > > 
> > > > ----
> > > > $ make -j24 ARCH=i386
> > > >     :
> > > >    LD      drivers/built-in.o
> > > >    LINK    vmlinux
> > > > ./.config: line 44: $'\r': command not found
> > > I wonder whether my email client added ^Ms to the file that I send. It
> > > shouldn't have.
> > > 
> > > > Makefile:929: recipe for target 'vmlinux' failed
> > > > make: *** [vmlinux] Error 127
> > > > ----
> > > > 
> > > > Do you have steps to reproduce the issue?  Or do you see it during boot
> > > > -time?
> > > This always happens just after system has booted, it may still be going
> > > over
> > > init scripts. I am booting with ramdisk, don't know whether it has
> > > anything
> > > to do with this problem.
> > > 
> > > FWIW, it looks like pmd_pfn_mask() inline is causing this. Reverting it
> > > alone makes this crash go away.
> > Could you check the patch below?
> 
> 
> I does fix the problem on baremetal, thanks. My 32-bit Xen guests still 
> fail which I thought was the same issue but now that I looked at it more 
> carefully it has different signature.

I do not think Xen is hitting this, but I think page_level_mask() has the same
issue for a long time.  I will set up 32-bit env on a system with >4GB memory to
verify this.

Thanks,
-Toshi

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