From mboxrd@z Thu Jan  1 00:00:00 1970
From: Olaf Hering <olaf@aepfle.de>
Subject: Re: [PATCH v5 0/9] toolstack-based approach to pvhvm
	guest kexec
Date: Wed, 7 Jan 2015 10:10:57 +0100
Message-ID: <20150107091057.GA12049@aepfle.de>
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To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Andrew Jones <drjones@redhat.com>, Julien Grall <julien.grall@linaro.org>, Wei Liu <wei.liu2@citrix.com>, Ian Campbell <ian.campbell@citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Andrew Cooper <andrew.cooper3@citrix.com>, Ian Jackson <ian.jackson@eu.citrix.com>, Tim Deegan <tim@xen.org>, David Vrabel <david.vrabel@citrix.com>, Jan Beulich <jbeulich@suse.com>, xen-devel@lists.xenproject.org, Keir Fraser <keir@xen.org>
List-Id: xen-devel@lists.xenproject.org

On Mon, Jan 05, Vitaly Kuznetsov wrote:

> Wei Liu <wei.liu2@citrix.com> writes:
> 
> > Olaf mentioned his concern about handling ballooned pages in
> > <20141211153029.GA1772@aepfle.de>. Is that point moot now?
> 
> Well, the limitation is real and some guest-side handling will be
> required in case we want to support kexec with ballooning. But as David
> validly mentioned "It's the responsibility of the guest to ensure it
> either doesn't kexec when it is ballooned or that the kexec kernel can
> handle this". Not sure if we can (and need to) do anything hypevisor- or
> toolstack-side.

One approach would be to mark all pages as some sort of
populate-on-demand first. Then copy the existing assigned pages from
domA to domB and update the page type. The remaining pages are likely
ballooned. Once the guest tries to access them this should give the
hypervisor and/or toolstack a chance to assign a real RAM page to them.

I mean, if a host-assisted approach for kexec is implemented then this
approach must also cover ballooning.


Olaf