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Re: [Xen-devel] Re: [PATCH] Xen Guest Kexec

On Mon, Mar 06, 2006 at 03:15:00PM +0100, Gerd Hoffmann wrote:
>  * Which events can change the p2m map?  I think for domU that is only
>    ballooning, right?  For dom0 additionally the backend drivers (when
>    mapping foreign pages).  Anything else?

Networking as well, since network packet reception involves flipping
pages between domains.

>  * Is there some way to rebuild the p2m map from scratch using
>    hypercalls?

As far as I know not completely reliably, since the P2M map is
maintained by the guest and Xen is almost entirely uninvolved.

You could probably get most of the way there by retrieving a list of
pages belonging to the guest (not sure if this can be done from within
an unprivileged guest though, or only in Domain-0), then building a
reverse map of entries in the M2P table.  This will only work if all
pages have accurate M2P entries (certainly won't work for domain-0,
since it maps foreign pages, but might work for unprivileged domains).

--Michael Vrable

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