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Re: [XenARM] Which ARM architecture is plannet to be supported.

To: "sbuk.suh@xxxxxxxxxxx" <sbuk.suh@xxxxxxxxxxx>
Subject: Re: [XenARM] Which ARM architecture is plannet to be supported.
From: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
Date: Wed, 28 Sep 2011 17:33:43 +0100
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On Mon, 2011-09-26 at 03:02 +0100, 서상범 wrote:
> Hi,
> Xen ARM source code based on ARM v7 with multicore support has recently been 
> changed 
> so that CPU architecture independent code of x86 based Xen mainline will be 
> shared 
> I have a plan to support the future Cortex A15 virtualization extension.

This in an interesting topic.

Over the last few weeks I (and a few others) have been hacking on a
proof-of-concept hypervisor port to ARMv7 which uses the virtualization
extensions from the ground up (i.e. requires them).

The idea was to see if it was possible to build a system where all
guests (including domain 0) ran fully virtualized, although obviously a
PVonHVM style system would be the eventual target. The virtualization
extensions for ARMv7 appear to be sufficiently featureful to allow this
from day 1 (unlike, for example, when Xen began on x86).

It's a bit fast and lose in places but at the moment it is at the stage
where it can boot an (unmodified) Linux dom0 kernel at least as far as
running C code in start_kernel() on an emulator.

Since we were aiming for a virt-extn target only we didn't actually base
it on the existing ARM port, although obviously we took some inspiration
from parts of it.

I hope to have a couple of patch series worth posting to xen-devel and
lkml by the end of the year but in the meantime the Xen side code is at
        git://xenbits.xen.org/people/ianc/xen-unstable.git devel/arm

There are no Linux side patches yet but eventually we will want to
enable PV drivers etc.

I'm going to be at XenSummit Asia, we should meet and talk about how we
can merge these two efforts etc.


> On the other hand, I have released Xen ARM hypervisor source code since 2008, 
> which includes ARM v5, v6 and the para-virtualized ARM Linux kernel patch.
> These source code can be found at the Xen ARM wiki of Xen.org.
> Considering performance issues in terms of CPU overhead, context switching 
> overhead due to cache architecture and 
> CPU architecture such as multicore support issues,
> I think that it is better for ARM v5 and v6 Xen ARM hypervisor source code to 
> not be merged with the Xen mainline.
> I suggest to use the archieved Xen ARM hypervisor for ARM v5 and v6 at the 
> Xen ARM wiki.
> Thank you,
> Sang-bum
> ===============================================================
> Sang-bum Suh, PhD
> Vice President, S/W Platform Lab
> S/W Platform Team, DMC Research Center
> Samsung Electronics
> email: sbuk.suh@xxxxxxxxxxx
> ===============================================================
> ------- Original Message -------
> Sender : Jean-Christophe DUBOIS<jcd@xxxxxxxxxxxxxxx> 
> Date   : 2011-09-24 05:29 (GMT+09:00)
> Title  : [XenARM] Which ARM architecture is plannet to be supported.
> Hello,
> Just out of curiosity is this project only planning on supporting the ARMv7 
> architecture or are ARMv5 and v6 still part of the plan?
> Thanks.
> JC
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