Xen devel - Aug 2007 - Problem with (Mini-OS) page-table setup

Hello,

  I''m  working  on small  kernel  on  top of  Xen,  and  am having 
serious
headaches  after upgrading  from  Xen 3.0.3  to  Xen-unstable. The  problem
appears while I''m trying to extend my initial page-table. 

  In fact, my  page-table code was strongly based on  Mini-OS'' code. I
have
tried to boot  Mini-OS (as DomU) in my environment  with similar amounts of
memory (from  1024 to 2048  MiB) and Mini-OS  also crashes in  an analogous
form.  When it tries to extend its initial page-table for a
"demand-paging"
area, it dies with:

"PTE for new page table page could not be updated"

  After an  unsuccessful mmu_update() call. This  is what I get  in the xen
console:

(XEN) /home/liviobs/xen-unstable.hg/xen/include/asm/mm.h:186:d43 Error pfn
24000: rd=ffff8300cee12100, od=ffff8300ceef2100, caf=80000002,
taf=00000000e8000001
(XEN) mm.c:649:d43 Error getting mfn 24000 (pfn 2031c) from L1 entry
0000000024000125 for dom43

  While trying smaller memory sizes (16MiB, for example), everything works.

  I am at loss  at what could be the problem. I''ve  tried make sure my
page
table pages  have been marked  as read-only before calling  mmu_update() to
update  the higher-level level  page-table entry.  I''ve trying  pinning
the
page after making it read-only;  I''ve trying starting a new page-table
from
scratch and switching to it later. 

  If anyone can give me some tips  as to what could be going wrong, I would
really  appreciate it...  starting with  trying  to make  Mini-OS work  for
larger memory sizes  (I''ve actually been able to  reproduce this issue
with
128MiB). 

  My environment:

Host: Intel x86_64
Xen: unstable (changeset: 15521:1f348e70a5af)
GCC: 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)
Dom0: Linux 2.6.18 (changeset: 103:a70de77dd8d3)

  Thanks and don''t hesitate to bug me,


			    Livio

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On 1/8/07 22:17, "Livio Soares" <livio@eecg.toronto.edu> wrote:
>   After an  unsuccessful mmu_update() call. This  is what I get  in the xen
> console:
> 
> (XEN) /home/liviobs/xen-unstable.hg/xen/include/asm/mm.h:186:d43 Error pfn
> 24000: rd=ffff8300cee12100, od=ffff8300ceef2100, caf=80000002,
> taf=00000000e8000001
> (XEN) mm.c:649:d43 Error getting mfn 24000 (pfn 2031c) from L1 entry
> 0000000024000125 for dom43
The problem is that the given MFN (the one you are trying to map) does not
belong to you. Add some extra tracing around mm.h:186 and find out the
domain ids involved. This could be due perhaps to a bogus lookup in the p2m
map?

 -- Keir



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At 06:57 +0100 on 02 Aug (1186037839), Keir Fraser
wrote:
> On 1/8/07 22:17, "Livio Soares" <livio@eecg.toronto.edu>
wrote:
> >   After an  unsuccessful mmu_update() call. This  is what I get  in
the xen
> > console:
> > 
> > (XEN) /home/liviobs/xen-unstable.hg/xen/include/asm/mm.h:186:d43 Error
pfn
> > 24000: rd=ffff8300cee12100, od=ffff8300ceef2100, caf=80000002,
> > taf=00000000e8000001
> > (XEN) mm.c:649:d43 Error getting mfn 24000 (pfn 2031c) from L1 entry
> > 0000000024000125 for dom43
> 
> The problem is that the given MFN (the one you are trying to map) does not
> belong to you. Add some extra tracing around mm.h:186 and find out the
> domain ids involved. This could be due perhaps to a bogus lookup in the p2m
> map?
Xen-unstable changeset 15675:bf85b467ee89 may affect this, if you''re
using a 64-bit mini-os.

Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@xensource.com>, XenSource UK Limited
Registered office c/o EC2Y 5EB, UK; company number 05334508

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