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Re: [Xen-devel] Design question for PV superpage support

To: Dave McCracken <dcm@xxxxxxxx>
Subject: Re: [Xen-devel] Design question for PV superpage support
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Mon, 02 Mar 2009 17:37:26 -0800
Cc: Xen Developers List <xen-devel@xxxxxxxxxxxxxxxxxxx>, Mick.Jordan@xxxxxxx
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Dave McCracken wrote:
My understanding of save/restore is that it will save your carefully selected 2M pages, cheerfully restore them onto a random set of mfns, then expect your guest to continue running. I haven't studied it enough to know whether your guest at least gets a chance to intervene and fix things after the restore.

Your guest would need to be in the position to allocate an extra 512 L1 pte pages to replace each shattered 2M page, which could be awkward - and wouldn't have any realistic way to continue if it fails to do so. Perhaps some kind of special pool of pages could be provided to the domain to help it satisfy its memory needs in recovering from a restore-shattered large page.


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