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RE: [Xen-devel] BUG grant_table.c line 939

To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>
Subject: RE: [Xen-devel] BUG grant_table.c line 939
From: "King, Steven R" <steven.r.king@xxxxxxxxx>
Date: Tue, 24 Jan 2006 09:03:56 -0800
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
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Thread-topic: [Xen-devel] BUG grant_table.c line 939
Hi Keir, thanks for helping.
I'm not using shadow tables.  Before the Xen crash, Xen kills both of my
domUs via arch/x86/mm.c line 614.  Apparently my domUs are misbehaving
by not explicitly unmapping granted pages.  Because of the
domain_crash() call in mm.c, no form of put_page() is ever called for
the mapping.  Is this info helpful?

-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Keir Fraser
Sent: Tuesday, January 24, 2006 3:43 AM
To: King, Steven R
Cc: xen-devel
Subject: Re: [Xen-devel] BUG grant_table.c line 939

On 23 Jan 2006, at 21:13, King, Steven R wrote:

> After trials and tribulations getting my serial ports in order, I'm 
> finally able to report on a Xen crash I've been seeing.
> I have two domUs that share & map grant references with each other, 
> then both domUs crash.  Shortly thereafter, Xen crashes too.
> With dead domUs, the grant references they once held are left
> Xen isn't provisioned to mop this up, hence the well placed 
> BUG(rd==NULL).  Make any sense?  I'd be over my head to submit a patch

> for this, so I'm hoping for help.

Let's say domain A maps pages belonging to domain B (implying that B
granted access to A).

If B crashes then the domain should stick around as a zombie until all
mappings of its pages by other domains have gone away. This should mean
that if A crashes or dies and calls gnttab_release_mappings(), it should
not be possible for B to have disappeared at that point, and
find_domain_by_id() should succeed.

Neither of your domains are running on shadow page tables, are they?

  -- Keir

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