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Re: [Xen-devel] Unplugging a dom0 vcpu and domain destruction

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: Re: [Xen-devel] Unplugging a dom0 vcpu and domain destruction
From: George Dunlap <dunlapg@xxxxxxxxx>
Date: Fri, 20 Feb 2009 18:59:06 +0000
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
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On Fri, Feb 20, 2009 at 6:15 PM, Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:
> Is it that the offline cpu still has a cr3 reference to a pagetable, and
> that's not being given up?  Or gdt?

But that would be a reference in Xen, would it not -- from the d0v1's
vcpu struct in Xen?

The last reference to the domain pages went away when d0v1 wrote to
one of its own l1e's.  So one of dom0's l1's still contained a
reference to those pages.  The curious bit is why they weren't
unmapped immediately if d0v1 wasn't online, and why they were unmapped
immediately when d0v1 came back online.

> In the pvops kernels we also keep a reference to the vcpu info structure,
> since we place it the kernel's memory rather than keeping it in the shared
> info structure.  For a while that had bugs that left zombie domains lying
> around, but I don't think anyone backported that stuff to 2.6.18.

Hmm, I'll take a look tomorrow and see if I can work out what those
two pages that were being kept are.

 -George

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