Re: [Xen-devel] [RFC 00/29] Support multiple ARM platforms in Xen

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

CCing George, Xen 4.3 release manager.

On Mon, 2013-04-29 at 00:01 +0100, Julien Grall wrote:
> Hello,
> 
> This patch series is divided in 4 parts:
>     - Patch 1-6: Minor bug fixes
>     - Patch 7-10: Add hierarchical device tree support based on linux tree
>     - Patch 11-24: Remove harcoded part
>     - Patch 25-28: Arndale support based on Anthony's git
> 
> Xen can boot on both Arndale Board and the Versatile Express without
> recompilation. But there is still some hardcoded part, mainly in assembly.

I haven't reviewed this yet but I think this is something we are going
to want for the Xen 4.3 release if at all possible. (NB, for Linaro
chaps, we are past feature and code freeze and are intending to release
4.3-rc1 next Monday, but there is scope for freeze exceptions to be
argued for)

Arndale is currently the only widely available/reasonably priced
development platform which can run Xen and therefore IMHO Xen 4.3 needs
to be able to run on it if it is to be a useful "tech preview" platform.

The current xen.git tree runs on the vexpress platform (rather
expensive) with the TC2 chip (difficult if not impossible for random
developers to get hold of) and the software models (random developers
can get an eval license for these, but they don't last very long). IMHO
the priority order of the platforms for 4.3 is, in decreasing order:
        Arndale
        Fast Models
        Vexpress
(with vexpress there running a pretty distant third)

Obviously there is a risk with these patches of breaking Xen on one or
more (or all) of those platforms: I think this is a risk we should take.

However this is not worth slipping the Xen release for, in particular it
is not reasonable to delay the release for x86 users because we took a
risk for a tech preview on ARM. So I propose that we take these patches
and see how it goes. I think in practice the rc cycle will be plenty of
time to sort out Xen on Arndale for 4.3, but the contingency plan would
be to fix it up in 4.3.1 and/or maintain a brief xen-on-arm fork of 4.3.

Ian.


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