Re: [Embedded-pv-devel] Xen with RTOS (such as Windows CE)

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

Hi,

On Mon, 2016-02-08 at 09:59 -0800, Emir Elkholy wrote:
> Currently we boot Windows CE from a dos bootable drive using a
> program called biosloader on our x86 Baytrail board (Intel). After
> the BIOS loads our USB stick (or SSD) with the Windows CE image is
> loaded by BIOSloader. Would Xen be able to load Windows CE in a
> similar fashion? 
>
So, I know nothing about Windows CE and how it's loaded.

In general, you can boot and use as *pure* HVM Xen guest any unmodified
operating system. Whether it will run well, it's another pair of hands
(and that is the case with every hypervisor, actually)

In fact, while CPU is probably going to be fine, for IO, having some
kind of paravirtualization in place would be desirable. And to achieve
that, you need the guest to support it, e.g. via specific drivers.
These drivers exists for Windows, but I've no idea whether they work on
CE too.

However, maybe you can just statically assign (by means of what we call
"PCI passthrough") the device that you need high performance from to
your WinCE guest, in which case the lack of paravirt IO would not be an
issue...

In summary, it's hard to tell, until someone tries. :-/

> Has Xen ever been used with an RTOS like Windows CE? 
>
People on this list have been working on using both QNX and Android as
Xen guest, but I don't personally know the exact status of this.

There also has been a port of FreeRTOS (although, on ARM):
http://www.xenproject.org/directory/directory/projects/240-GaloisInc-FreeRTOS-Xen.html

> I would like to use Xen to run linux for our GUI and Windows CE for
> our real-time code.Â
>
That's a very interesting use case, and Xen is certainly capable of
making it happen, if you can work out the issues above.

Things and features you may be interested in looking at are vcpu
pinning and/or vcpu hard and soft affinity, cpupools, and the RTDS
scheduler. Do ask about them either here or on the xen-users mailing
list (and keep me in Cc).

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
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Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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