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

To: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] Live migration leaves page tables read-only?
From: John Byrne <john.l.byrne@xxxxxx>
Date: Tue, 28 Nov 2006 18:52:41 -0800
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Ian Pratt wrote:
I forgot to mention that a very simple test case I wrote using shared
memory and the mprotect call didn't fail. So, the only test case I
have
at the moment is to run SAP.

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.)

In the meantime, any ideas where to look?


Also, can you repro on 32b?

I am doing this on behalf of someone else, so I'd have to ask them to do the setup if they have the time. I am reluctant to do so at this point.

Thanks,

John


Thanks,
Ian

John Byrne

John Byrne wrote:
I have been trying to debug a problem live-migrating SAP on
Xen-3.0.3
x86-64 (I also tested Xen-unstable changeset 12548) without success.

SAP seems to run fine on a given host; live-migrating it to another
host
causes the guest to almost immediately panic in the mprotect() call
in
the change_pte_range() routine in the set_pte_at() macro because the
page table page it is trying to update is write-protected.

My attempts at understanding where this is coming from have come to
naught. Any help in running this down would be appreciated. I am
perfectly willing/able to write some debugging code if I am given a
few
clues what to look for.

Thanks,

John Byrne




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