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[Xen-devel] Re: Balloons, crash-dumps, populate-on-demand, and shared ze

To: Steven Smith <Steven.Smith@xxxxxxxxxxxxx>
Subject: [Xen-devel] Re: Balloons, crash-dumps, populate-on-demand, and shared zero pages
From: Paul Durrant <paul.durrant@xxxxxxxxxx>
Date: Thu, 20 Aug 2009 11:56:05 +0100
Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Gianluca Guida <Gianluca.Guida@xxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <Keir.Fraser@xxxxxxxxxxxxx>
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Steven Smith wrote:
That would make things marginally easier on the drivers, but it's at
the expense of potentially more subtle errors when something goes
wrong.  At the moment, if the balloon driver tries to deflate the
balloon too far, the populate hypercall fails and it's very obvious
what's gone wrong, whereas with an implicit re-populate it'll look
like everything's working fine for some time afterwards, until the
guest touches too many pages and PoD kills it.

If the balloon driver deflated too far, that would be a bug in the balloon driver, and if Windows doesn't scrub the memory when it's freed we could do that ourselves so at least PoD would kill the guest at the right juncture.


Paul Durrant, Software Engineer

Citrix Systems (R&D) Ltd.
First Floor, Building 101
Cambridge Science Park
Milton Road
Cambridge CB4 0FY
United Kingdom


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