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Re: [Xen-devel] 2.6.29-rc7 pv_ops dom0 BUG / unable to handle kernel pag

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: Re: [Xen-devel] 2.6.29-rc7 pv_ops dom0 BUG / unable to handle kernel paging request
From: Pasi Kärkkäinen <pasik@xxxxxx>
Date: Thu, 12 Mar 2009 10:32:42 +0200
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On Wed, Mar 11, 2009 at 04:40:24PM -0700, Jeremy Fitzhardinge wrote:
> Pasi Kärkkäinen wrote:
> >On Wed, Mar 11, 2009 at 10:52:50PM +0200, Pasi Kärkkäinen wrote:
> >  
> >>On Sun, Mar 08, 2009 at 01:54:01PM +0200, Pasi Kärkkäinen wrote:
> >>    
> >>>On Sat, Mar 07, 2009 at 10:09:16PM -0800, Jeremy Fitzhardinge wrote:
> >>>      
> >>>>Pasi Kärkkäinen wrote:
> >>>>        
> >>>>>Hello!
> >>>>>
> >>>>>Latest git tree (updated some hours ago) boots up fine for me, xend 
> >>>>>can be started etc, but some time after starting kernel compilation I 
> >>>>>get the following BUG:
> >>>>>
> >>>>>http://pasik.reaktio.net/xen/pv_ops-dom0-debug/pv_ops-dom0-bootlog-19-xen331-linux-2.6.29-rc7-bug.txt
> >>>>>
> >>>>>(XEN) mm.c:2006:d0 Bad type (saw 28000001 != exp e0000000) for mfn 
> >>>>>436a3 (pfn 3d0a3)
> >>>>>(XEN) mm.c:707:d0 Error getting mfn 436a3 (pfn 3d0a3) from L1 entry 
> >>>>>00000000436a3063 for dom0
> >>>>>(XEN) mm.c:3640:d0 ptwr_emulate: could not get_page_from_l1e()
> >>>>>BUG: unable to handle kernel paging request at c01cbd58
> >>>>>IP: [<c0405d2f>] xen_set_pte+0x8c/0x96
> >>>>> 
> >>>>>          
> >>>>Well, that's bad news.  It was trying to map a highmem pte page which 
> >>>>didn't have the Pinned bit set on its page, but Xen thought it was a 
> >>>>pinned pte page.  Not sure how it could get into that state, but its 
> >>>>indicative of general memory corruption.
> >>>>
> >>>>What was going on at the time?  Was dom0 busy?  Were you running some 
> >>>>domUs?
> >>>>
> >>>>        
> >>>At that time I was compiling a kernel on dom0.. so dom0 was busy.
> >>>
> >>>No other domains running. 
> >>>
> >>>      
> >>Same thing happened again.. with the latest tree (as of today).
> >>
> >>Again I was compiling a kernel in dom0, so dom0 was busy. No other domains
> >>running. 
> >>
> >>    
> >
> >The exact same kernel booted on baremetal without Xen works OK, and doesn't
> >BUG during kernel compilation. 
> >
> >  
> That's good to know as a baseline, though the bug is Xen refusing to do 
> a pte update, so I'd be surprised if it happened with Xen in the picture ;)
> What happens if you disable CONFIG_HIGHPTE?

Ok. I'll try that later.. I'll be away for 1,5 weeks (going to a vacation), 
so can't try right now. 

One difference just came to my mind.. when booted on baremetal, whole 2G of
ram is available.. when booted as dom0 I've limited dom0 memory to 1G. 

I guess I should try with the same amount of memory available for both
dom0 and baremetal.

-- Pasi

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