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Re: [Xen-devel] [PATCH 0 of 5] update xenctx to dump pagetables

To: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 0 of 5] update xenctx to dump pagetables
From: Olaf Hering <olaf@xxxxxxxxx>
Date: Mon, 20 Jun 2011 19:51:58 +0200
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On Mon, Jun 20, Tim Deegan wrote:

> Hi, 
> At 17:26 +0200 on 20 Jun (1308590816), Olaf Hering wrote:
> > The code to walk the pagetables is/was based on
> > xc_translate_foreign_address(), but I still think I have some major bugs in
> > there (the last patch). I cant figure out why some l3/l2/l1 entries can not 
> > be mapped.
> > Any help with getting that output fixed for at least a a 64bit PV guest is 
> > much
> > appreciated.
> I didn't spot anything broken in the walker (though it will need a bunch
> of cleaning up) and the output looks very plausible.  I take it this is
> a PV guest?  Is it a well-behaved one or a broken post-migrate one?

Yes, its a PV guest. I cant reproduce the migrate crashes, it happens
only on very few systems or on a certain configuration. The logs I
posted are from my test system.
Any ideas why some mfns are not accessible?

Are there any other paging states maintained outside of the guests

> One thing that might be causing trouble is if the domain's not paused
> while you do the walk, then you might see inconsistent tables, though
> I'd expect them to be garbage rather than looking like this.  Your patch
> 3/5 does seem to make the pausing conditional where before it always
> happened. 

It tries it preserve the state, if the guest was paused it probably
should not be unpaused. Is the dominfo.paused flag somehow unreliable, I
thought it comes right from struct domain?

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