Re: [Xen-devel] Can xen support nommu cpu virtualization?

[Lei Wen <adrian.wenl@xxxxxxxxx>]

On Tue, Aug 14, 2012 at 9:35 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> On Tue, 2012-08-14 at 14:23 +0100, Lei Wen wrote:
>> Hi Ian,
>>
>> On Tue, Aug 14, 2012 at 9:06 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> 
>> wrote:
>> > On Tue, 2012-08-14 at 10:31 +0100, Lei Wen wrote:
>> >> Hi,
>> >>
>> >> I am a newbie for the XEN area and curious to know whether current XEN
>> >> could support nommu arch, or only MPU?
>> >> If current it doesn't support, does XEN have any plan or road map to
>> >> add this support in future?
>> >
>> > You should be able to run a NOMMU guest OS as an HVM guest today (or at
>> > least I can't think why it wouldn't work).
>> >
>> > There are no plans to make Xen itself usable on a no-MMU system, use of
>> > the MMU is pretty firmly baked into Xens architecture.
>>
>> Yep, I get your point. However, on modern embedded system, there are still
>> place for no-mmu arches, like the ARM cortex-r7 processor:
>> http://www.arm.com/products/processors/cortex-r/cortex-r7.php
>
> OK, you should have made it clear you were talking about ARM.
>
> The ARM port which I am involved with[0] requires the virtualisation
> extensions, which AFAIK are a ARMv7-A only and an MMU is always assumed
> (it's presence pretty much baked into the extensions in various ways).
> We have no plans to support non-mmu ports of this variant of Xen.
>
> The other ARM port (the PV port[1]) does not require virtualisation
> extensions, however the correct list for questions/discussion about that
> port is the xen-arm@ list.
>
> [0] http://wiki.xen.org/wiki/Xen_ARMv7_with_Virtualization_Extensions
> [1] http://wiki.xen.org/wiki/Xen_ARM_%28PV%29
>
>> So making such platform virtualised would have the business benefit, since
>> could reduce total embedded product BOM price.
>>
>> Do you have any guideline or idea that could make nommu possible? :)
>
> Even the ARM PV port makes extensive use of the MMU to provide isolation
> between guests (at least I presume so). If you want to work on nommu
> systems then it seems like this would be the first problem you would
> have to consider.
>

Understand. Thanks for your kindly reply. :)

Thanks,
Lei

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