linux-kernel - Re: Panic caused by PTE corruption

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Date:	Sun, 9 Jan 2011 10:05:26 -0600
From:	Jack Steiner <steiner@....com>
To:	Pasi Kärkkäinen <pasik@....fi>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org, cl@...ux.com
Subject: Re: Panic caused by PTE corruption - 2.6.32 distro kernel

On Sun, Jan 09, 2011 at 04:47:45PM +0200, Pasi Kärkkäinen wrote:
> On Sat, Jan 08, 2011 at 10:48:48PM -0600, Jack Steiner wrote:
> > 
> > A long shot but I'm hoping someone has seen corruption like this
> > before.
> > 
> > System is running a 2.6.32 distro kernel on a large x86_64 Nehalem system.
> >
> 
> Which exact kernel version/distro is this? 

SLES11SP1. The failures have occurred on both the latest update kernel
version & the update that was released in July (not sure of exact id).
I suspect the problem occurs on all update versions.


> 
> -- Pasi
> 
> > During the last 4+ months we have seen 3 instances of panic's caused by a
> > spurious bit 48 being set in a page table. So far, we are unable to
> > reliably duplicate the problem but it has occured on multiple systems. We
> > have not seen any other strange failures caused by memory corruption.  The
> > bug only hits bit 48 in PTEs.
> > 
> > Has anyone seen anything like this before or have any ideas? Note
> > that the system has several non-distro drivers. We have no
> > reason to believe these drivers are related but can't rule it out.
> > 
> > Here is a detailed analysis of the first failure. The other failures are
> > similar.
> > 
> > --------------------------------
> > 
> > Failure occurred because a user-mode page-table-walk found a page table
> > entry with a reserved bit set.
> > 
> >         <1> engine_par: Corrupted page table at address 20705808
> >         <4> PGD 7cf83c8b067 PUD 7ccd3170067 PMD 7e7f8c46067 PTE 800107e1d43f5067
> >         <0> Bad pagetable: 000f [#1] SMP
> >                               ^--- bit 3 ==> reserved bit is set in a PT entry
> > 
> >         PGD      7cf83c8b067
> >         PUD      7ccd3170067
> >         PMD      7e7f8c46067
> >         PTE 800107e1d43f5067
> >                ^------- ???
> > 
> > 
> > Note bit 48 in the PTE. This bit should not be set. Failure left no trace
> > that I could find.  Other observations:
> > 
> > Failing process is:
> >         0xffff8fcff6942140   237757   237716  1 1010   R  0xffff8fcff69427d0 *engine_par
> > 
> > Appears to be a big MPI job (hybrid???)
> > 
> > 
> > Other entries in the PT close to the corrupted entry look reasonable:
> >         0xffff8fe7f8c46800 800007e1d43f0067 800007e1d43f1067
> >         0xffff8fe7f8c46810 800007e1d43f2067 800007e1d43f3067
> >         0xffff8fe7f8c46820 800007e1d43f4067 800107e1d43f5067 << has bad entry
> >         0xffff8fe7f8c46830 800007e1d43f6067 800007e1d43f7067
> >         0xffff8fe7f8c46840 800007e1ab590067 800007e1ab591067
> >         0xffff8fe7f8c46850 800007e1ab592067 800007e1ab593067
> >         0xffff8fe7f8c46860 800007e1ab594067 800007e1ab595067
> >         0xffff8fe7f8c46870 800007e1ab596067 800007e1ab597067
> > 
> > 
> > A second failure:
> > 	0xffff8dbff5a34a70 800005bcdd382067 800005bcdd383067
> > 	0xffff8dbff5a34a80 800005bcdd384067 800005bcdd385067
> > 	0xffff8dbff5a34a90 800005bcdd386067 800005bcdd387067
> > 	0xffff8dbff5a34aa0 800005bcdd388067 800105bcdd389067  << has bad entry
> > 	0xffff8dbff5a34ab0 800005bcdd38a067 800005bcdd38b067
> > 	0xffff8dbff5a34ac0 800005bcdd38c067 800005bcdd38d067
> > 	0xffff8dbff5a34ad0 800005bcdd38e067 800005bcdd38f067
> > 	0xffff8dbff5a34ae0 800005bcdd390067 800005bcdd391067
> > 
> > ---
> > Jack Steiner (steiner@....com)
> > SGI - Silicon Graphics, Inc.
> > 
> > --
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