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

["Jean-Christophe DUBOIS" <jcd@xxxxxxxxxxxxxxx>]

Hello Sang-burn,

Thanks for your answer. 

If I read you correctly, Xen on ARM for ARMv5 and ARMv6 does not seem good 
performance wise. Do you have some benchmarks on this topic (Linux bare metal 
compared to Linux on top of Xen)? Obviously the lack of virtualization 
features on these processors mandates the use of a para-virtualized low level 
API that may certainly have its drawbacks. 

Now excuse my ignorance but it seems other hypervisors out there (the L4 
familly for example) have acceptable performance hit when it comes to running 
Linux on ARM. In addition you may want to consider that for certain type of 
application the use of an hypervisor may not be driven only by performance 
reasons. Hypervisors are bringing other types of benefits/services.  An there 
are a lot of devices out there which are not ARMv7 based and that would be too 
bad to let them Xen-orphaned.

Beside Xen still supports generic x86 (32 bits) architecture which for the 
most part has no hardware support for virtualization and therefore also need 
to take the para-virtualization way with the same kind of performance hit I 
guess. Is it real worse on ARM?

As for cortex A15 it is "just" another ARMv7 processor with added 
virtualization features so it certainly make sense to add support for it after 
the CortexA8/A9 is done. But there will not be a lot of people out there able 
to help as the access to such hardware will be scarce at first.

Regards

JC

On Monday 26 September 2011 04:02:01 you 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.
> 
> 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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