Re: [ARM] Native application design and discussion (I hope)

From: Julien Grall <julien.grall@arm.com>
To: Stefano Stabellini <sstabellini@kernel.org>,
	George Dunlap <george.dunlap@citrix.com>
Cc: Volodymyr Babchuk <vlad.babchuk@gmail.com>,
	Dario Faggioli <dario.faggioli@citrix.com>,
	Artem Mygaiev <joculator@gmail.com>,
	Andrii Anisov <andrii_anisov@epam.com>,
	Xen Devel <xen-devel@lists.xen.org>
Subject: Re: [ARM] Native application design and discussion (I hope)
Date: Mon, 8 May 2017 19:33:26 +0100	[thread overview]
Message-ID: <1f7ab033-ca6c-d5fc-0fce-cafff16e9663@arm.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1705081128050.24729@sstabellini-ThinkPad-X260>

On 05/08/2017 07:31 PM, Stefano Stabellini wrote:
> On Mon, 8 May 2017, George Dunlap wrote:
>> On 05/05/17 20:28, Stefano Stabellini wrote:
>>> On Fri, 5 May 2017, Andrii Anisov wrote:
>>>> Hello Stefano,
>>>>
>>>> On 24.04.17 21:08, Stefano Stabellini wrote:
>>>>> Stubdomains (stubdoms in short) are small domains, each running a single
>>>>> application. Typically they run unikernels rather than a full fledged
>>>>> operating system. A classic example is QEMU stubdoms on x86: one QEMU
>>>>> stubdoms is started for each regular guest domain. Each QEMU stubdom
>>>>> instance provides emulation for one guest - it runs one instance of
>>>>> QEMU.
>>>> I'm wondering if there are any examples of practical usage of stub domains
>>>> with ARM?
>>>
>>> Good question. I don't think so: there have been practical examples of
>>> unikernels running on Xen on ARM, but not stubdoms, because we haven't
>>> needed to run large emulation pieces yet.
>>
>> So often when we say "stub domains" we mean specifically, "devicemodel
>> stub domains".  But there are many other stub domains for other
>> purposes.  You can run xenstored in a stubdomain rather than in dom0,
>> for instance; I think this probably already works on ARM.  I believe
>> that the PV vTPM architecture also has one vTPM "worker" per guest,
>> along with a "global" domain to control the physical TPM and multiplex
>> it over the various vTPMs.
>
> TPM is an x86 concept, but xenstored stubdom is possible.
>
> Althought they don't have to, stubdoms are typically based on mini-os
> (git://xenbits.xen.org/mini-os.git) which only has 32-bit ARM support
> today. However, it should be possible to run a 32-bit stubdom on a
> 64-bit host.

The 32-bit ARM support in Mini-OS has never been completed. Hopefully
someone will finish it soon.

Cheers,

-- 
Julien Grall

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