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Re: [Xen-devel] Question: dom0 electrocuted by implicitly unmapped grant

To: Daniel Stodden <daniel.stodden@xxxxxxxxxx>, Xen Developers <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Question: dom0 electrocuted by implicitly unmapped grantrefs
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Mon, 23 Nov 2009 22:52:31 +0000
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On 23/11/2009 22:43, "Daniel Stodden" <daniel.stodden@xxxxxxxxxx> wrote:

> I assume 'implicitly unmapped' therein refers to a case where rd is gone
> because ld in some or the other way already managed to tear down a
> mapping without an exlicit gnttab call? This correct? Otherwise killing
> ld would seem a bit rough to me :}

You are correct.

> Either way: is domain_crash(ld) the appropriate response? Why not just
> fail the op and let the caller live and learn?

It's arguable I suppose. An implicitly unmapped grant leaves a grant entry
which cannot be released until the mapping domain dies. It's a nasty kind of
leak, and I made the hypervisor's response to it suitably abrupt.

 -- Keir



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