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RE: [Xen-devel] Live migration leaves page tables read-only?

To: "John Byrne" <john.l.byrne@xxxxxx>, <ian.pratt@xxxxxxxxxxxx>
Subject: RE: [Xen-devel] Live migration leaves page tables read-only?
From: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Date: Fri, 1 Dec 2006 01:13:01 -0000
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
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Thread-topic: [Xen-devel] Live migration leaves page tables read-only?
> >> What happens if you use non-live relo?
> >
> > I thought I had tested that way back at the beginning without seeing
the
> > problem, but I must not have, because I just retested it to be sure
and
> > it died the same way. (Now I am truly confused and I need to go back
and
> > re-examine some of my earlier experiments.)
> >
> 
> After redoing some of my tests and understanding more about how Xen
> handles page tables, I started looking at ptwr_do_page_fault() and put
> debugging code into it. (On Xen 3.0.3 x86-64.)  The fixup is failing
in
> x86_emulate_memop(). Building a debug version of Xen provided some
> additional information (the final line is from my debugging, after the
> ":" is domid, addr, pte, pte flags, type_info, page owner, domain):

You say you can repro the problem using non-live relo. In that case, you
should also be able to repro it using save/restore, which has almost
identical code paths.

Please try and isolate whether the crash happens on save or restore, and
further whether a given saved images crashes every time in the same way
when you try and restore it (mfns will be different, but pfns may be the
same).

 
Ian


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