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[Xen-devel] Re: scrubbing pages on vm pause

To: Joanna Rutkowska <joanna@xxxxxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] Re: scrubbing pages on vm pause
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 25 May 2010 15:19:51 +0100
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Rafal Wojtczuk <rafal@xxxxxxxxxxxxxxxxxxxxxx>
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On 25/05/2010 15:19, "Joanna Rutkowska" <joanna@xxxxxxxxxxxxxxxxxxxxxx>

> Let's consider this scenario:
> xm save domain1
> xm create domain2
> Can the domain2 get *unscrubbed* pages that were previously used by
> domain1, but were not scrubbed properly by domain1?

Generally speaking a domain loses pages to the free pool in only two ways:
via a decrease_reservation hypercall, and via domain destruction. In the
former case the domain itself is responsible for first scrubbing the page.
In the latter case Xen is responsible. With both avenues covered, domain2
cannot get unscrubbed pages from domain1.

 -- Keir

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