Re: [Qemu-devel] [PATCH 00/10] xen: pv domain support.

From: Gerd Hoffmann <kraxel@redhat.com>
To: Alexander Graf <agraf@suse.de>
Cc: qemu-devel <qemu-devel@nongnu.org>,
	xen-devel@lists.xensource.com, Avi Kivity <avi@redhat.com>,
	Laurent Vivier <Laurent@vivier.eu>
Subject: Re: [Qemu-devel] [PATCH 00/10] xen: pv domain support.
Date: Mon, 06 Apr 2009 09:10:50 +0200	[thread overview]
Message-ID: <49D9AAFA.606@redhat.com> (raw)
In-Reply-To: <803692EA-B562-4D41-A809-7EF552180B8F@suse.de>

Alexander Graf wrote:
> 1) Migration path. If you could already use KVM on a Xen host, you could
> have Xen PV guests and KVM guests in parallel, easing migration to KVM
> for customers.

I still plan to make xenner handle that use case.
You can also run xen inside kvm via nested svm.

> 2) Alternative to HVM. That's how this came up from Gerd's mail. We do
> have KVM support in upstream qemu, but we don't have Xen HVM support.
> That way you could use the same binary for all your needs. Admittedly,
> it might make more sense to just implement HVM support :-).

HVM is more difficuilt.  Xen considers the tools <-> hypervisor
interface private, i.e. it is a moving target.  For PV this isn't a big
issue as there is little reason to actually change something.  HVM
usually has quite a few changes from release to release though, due to
emulation changes/improvements and other reasons.

cheers,
  Gerd