From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: [PATCH 1/2] PV hugepages - Xen patch
Date: Wed, 08 Oct 2008 15:50:56 -0700
Message-ID: <48ED3950.1080605@goop.org>
References: <C512B667.1DFE2%keir.fraser@eu.citrix.com>
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To: Keir Fraser <keir.fraser@eu.citrix.com>
Cc: Ian Pratt <Ian.Pratt@eu.citrix.com>, Dave McCracken <dcm@mccr.org>, xen-devel@lists.xensource.com
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Keir Fraser wrote:
> Actually this is an interesting one. For a PV guest it may be in general
> unsolvable, since the target machine may not have allocatable 2MB extents.
> It may also screw live migration since 2MB is a very coarse granularity to
> do dirty-page tracking. One option: perhaps the PV kernel could shatter and
> then reconstruct (as best it can) superpage mappings across save/restore?

That means you need to notify the guest when you're starting a live 
migration, rather than just springing it on them at the last moment as 
we do now.

But shattering large pages all over the place is going to be pretty 
expensive, and possibly awkward if it suddenly needs to come up with a 
pile of pages for the new L1 entries.

    J