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GSOC2011 project RTEMS HyperVisor



I don't know if it is formally documented about LGPL, but it was
discussed recently, see the mailing list thread:
http://www.rtems.com/ml/rtems-users/2010/april/thrd1.html#00066

My understanding is that as long as there is (1) a linking exception,
(2) no obligatory advertisement clauses, and (3) no requirement to
redistribute modifications to the licensed software (e.g. source
upstream / publish any changes made), then the license is fine.  LGPL
requires #3 from what I can tell, and a minor version of #2 (prominent
acknowledgement of included libraries, whatever the definition of
prominent).

Informally, the closest (safest) license is actually the FreeBSD
(2-clause BSD) license.  The 3-clause BSD is also fine, since its
advertisement clause is actually a restriction on using names, rather
than an obligation.

-Gedare

On Mon, Mar 21, 2011 at 3:17 PM, Tobias Schoofs <Tobias.Schoofs at gmx.net> wrote:
> Mh. Why do you say that LGPL is insufficient for RTEMS? RTEMS is based on GPL with an exception that is similar to the "Lesser".
>
> Actually, for the code directly linked to RTEMS (MMU, superuser mode), the license will be the license of the modules that are changed (the SPARC-LEON BSP, for instance) and hence, the RTEMS license.
>
> For our own code, the plan is to use an "RTEMS-friendly" license that is widely used.
>
> You say "it was established" that LGPL is not sufficient. Is this documented somewhere? Is there perhaps a rationale for license-related decisions?
>
> Thanks,
>
> Tobias
>
> -------- Original-Nachricht --------
>> Datum: Mon, 21 Mar 2011 12:34:39 -0400
>> Von: Gedare Bloom <gedare at gwmail.gwu.edu>
>> An: Tobias Schoofs <Tobias.Schoofs at gmx.net>
>> CC: "?? ???? ?" <157724595 at 163.com>, rtems-users at rtems.org
>> Betreff: Re: RE: GSOC2011 project RTEMS HyperVisor
>
>> I think it was established that LGPL is not sufficient for RTEMS code
>> base. I believe this makes an AIR-based project an unlikely candidate
>> for a GSOC project. Especially if the student used the AIR kernel as a
>> resource. ?Perhaps if the AIR kernel is released under an
>> RTEMS-friendly license, a suitable project might be possible.
>>
>> Even if a "clean room" implementation of a hypervisor is the intended
>> project, I'm not sure it is appropriate for a GSOC at this point in
>> time. ?My guess is that using RTEMS as a hypervisor requires three
>> sub-projects that are all at or beyond the scope of a single GSOC:
>>
>> 1) Adding virtual memory / MMU support to RTEMS is a necessary
>> pre-requisite to any attempt at making a true hypervisor, and it is a
>> large project by itself.
>>
>> 2) Adding privileged/unprivileged distinction is also a pre-requisite
>> to implementing a hypervisor. Each candidate target will have to be
>> identified, and the CPU-specific context switching and interrupt
>> handling would need some tweaking to ensure that privilege bits are
>> properly managed. As far as I know, most processors just have full
>> privilege for the application at all times. This is a large project by
>> itself.
>>
>> 3) Implement the hypervisor itself involves primarily copying of page
>> tables, swapping out guests, exporting a HAL (device drivers), and
>> writing handlers for paravirtualized exceptions, hypercalls, and true
>> guest exceptions. ?This is also a large project.
>>
>> -Gedare
>>
>>
>> On Mon, Mar 21, 2011 at 10:57 AM, Tobias Schoofs <Tobias.Schoofs at gmx.net>
>> wrote:
>> > 1) Yes, it does. There is a library that implements all services from
>> ARINC 653 Part 1 and a subset of Part2. This library, however, is closed
>> software.
>> >
>> > 2) The AIR kernel is Lesser GPL and, as such, open source.
>> >
>> > 3) The code will be release very soon, i.e. in the course of the next
>> months.
>> >
>> > I will provide more information in an e-mail directly to you, since this
>> is not of general interest to the mailing list.
>> >
>> > Regards,
>> >
>> > Tobias
>> >
>> > -------- Original-Nachricht --------
>> >> Datum: Mon, 21 Mar 2011 22:07:39 +0800 (CST)
>> >> Von: "???" <157724595 at 163.com>
>> >> An: "Tobias Schoofs" <Tobias.Schoofs at gmx.net>
>> >> CC: Jean-Jacques.Metge at cnes.fr, rtems-users at rtems.org
>> >> Betreff: RE: GSOC2011 project RTEMS HyperVisor
>> >
>> >> Dear Tobias:
>> >> Thanks for your replay, actually i misunderstand the AIR system. And
>> the
>> >> work AIR system has done is what i want to implement. My thought is
>> also
>> >> to implement a para-virtualisation hypervisor that can run RTEMS and
>> other
>> >> OS.(RTEMS as a guest OS). I do not plan to implement a
>> full-virtualisation
>> >> hypervisor.
>> >> I has some question about AIR:
>> >> 1). AIR has also implement the ARINC 653 APEX on RTEMS?
>> >> 2). All the AIR source code is released ?under GPL?
>> >> 3). When does AIR source code released? could you send me a copy of
>> source
>> >> code foracademic research now?
>> >>
>> >> Wenjie
>> >> Best Regards
>> >>
>> >>
>> >>
>> >>
>> >> At 2011-03-21 21:43:52?"Tobias Schoofs" <Tobias.Schoofs at gmx.net>
>> wrote:
>> >>
>> >> >Dear Wenjie,
>> >> >
>> >> >your understanding of the AIR system is not 100% correct.
>> >> >
>> >> >AIR is a hypervisor that uses para-virtualisation.
>> >> >
>> >> >RTEMS is a guest OS for this hypervisor. The guest has to be prepared
>> >> (para-virtualised) to run on top of the hypervisor. RTEMS is currently
>> our
>> >> main target, but there may be other OSes as well (e.g. Linux).
>> >> >
>> >> >Finally, the AIR hypervisor uses RTEMS *additionally* as hardware
>> >> abstraction layer (HAL), i.e. the hypervisor itself is based on RTEMS.
>> For this
>> >> purpose, we have implemented MMU support as well as superuser/user
>> level
>> >> support in RTEMS.
>> >> >
>> >> >The code is under Lesser GPL and will be made available to the RTEMS
>> >> community.
>> >> >
>> >> >From one of your previous e-mails, I got the impression that you plan
>> a
>> >> hypervisor that does run-time virtualisation. (You mentioned that you
>> do not
>> >> want to change the guest OS.) I am not sure that you will be able to
>> >> provide sufficient certification/qualification evidence for such a
>> complex
>> >> software. At least in areas where ARINC 653 is applied,
>> >> certification/qualification processes are very demanding. For this
>> reason, available, commercial
>> >> hypervirsors (VxWorks 653, PikeOS) use para-virtualisation, not full
>> run-time
>> >> virtualisation.
>> >> >
>> >> >Regards,
>> >> >
>> >> >Tobias
>> >> >
>> >> >
>> >> >-------- Original-Nachricht --------
>> >> >> Datum: Mon, 21 Mar 2011 20:31:31 +0800 (CST)
>> >> >> Von: "???" <157724595 at 163.com>
>> >> >> An: "Metge Jean-Jacques" <Jean-Jacques.Metge at cnes.fr>
>> >> >> CC: RTEMS Users <rtems-users at rtems.org>
>> >> >> Betreff: RE: GSOC2011 project RTEMS HyperVisor
>> >> >
>> >> >> AIR/AIR IIseems that it hasimplemented ARINC 653 interface in RTEMS,
>> >> but i
>> >> >> do
>> >> >> not know if these implements is opened. If it is opened we also
>> modify
>> >> >> their work,
>> >> >> Because ARINC 653 interface should be based on Hypervisor
>> architecture
>> >> >> whereas
>> >> >> AIR implement is based on native RTEMS. XtratuM is a independent
>> >> >> Hypervisor which
>> >> >> has nothing to do with other OS, but my thought is to add a
>> Hypervisor
>> >> to
>> >> >> RTEMS. Just
>> >> >> reference the implement of XtratuM
>> >> >>
>> >> >>
>> >> >> At 2011-03-21 16:21:12?"Metge Jean-Jacques"
>> >> <Jean-Jacques.Metge at cnes.fr>
>> >> >> wrote:
>> >> >> ?
>> >> >> Hi,
>> >> >>
>> >> >> For my information, what do you exactly intend to do in the frame of
>> >> this
>> >> >> GSOC, that would not have been already done, either in the frame of
>> >> AIR/AIR
>> >> >> II or in the frame of XtratuM ?
>> >> >>
>> >> >> Best regards
>> >> >>
>> >> >> Jean-Jacques METGE
>> >> >> French Space Agency
>> >> >>
>> >> >>
>> >> >> De :rtems-users-bounces at rtems.org
>> >> [mailto:rtems-users-bounces at rtems.org]De
>> >> >> la part de ???
>> >> >> Envoy? : dimanche 20 mars 2011 14:57
>> >> >> ? : ???
>> >> >> Cc : RTEMS Users
>> >> >> Objet : Re:GSOC2011 project RTEMS HyperVisor
>> >> >>
>> >> >>
>> >> >> Sorry for forgetting add the reference link.
>> >> >> [1]. http://www.rtems.com/wiki/index.php/RTEMSHyperVisor
>> >> >> [2]. http://air.di.fc.ul.pt/air/?Home
>> >> >> [3].http://www.xtratum.org/
>> >> >> [4]. http://www.helenos.org/
>> >> >>
>> >> >>
>> >> >> At 2011-03-20 21:50:39?"???" <157724595 at 163.com> wrote:
>> >> >> Hi, all:
>> >> >> I am a student who is preparing for participating the GSOC2011
>> RTEMS.
>> >> My
>> >> >> interested project isRTEMS HyperVisor [1]. This
>> >> >> project ?s ultimate goal is to make RTEMS support to run multiple
>> >> >> operating systems?like Linux or uclinux) and meantime RTEMS can be
>> >> >> adapted to fullfill the requirements defined in the ARINC 653
>> standard.
>> >> So
>> >> >> the project is divided into two milestone tasks: 1) add a HyperVisor
>> to
>> >> >> RTEMS. the design of HyperVisor is compatible with ARINC 653
>> standard.
>> >> 2).
>> >> >> implement ARINC 653 interface in
>> >> >> RTEMS which can reference the a ESA project named AIR[2].
>> >> >> Hypervisor, also called virtual machine monitor (VMM), is one of
>> >> >> virtualization techniqueswhich allow multiple operating systems.
>> >> >> For embedded systems it must have real-time capability. And there is
>> >> also
>> >> >> a challenge to the resource-constrained embedded
>> >> >> systems, becausesupport for virtualization requiresmemory protection
>> >> (in
>> >> >> the form of a memory management unit or at least a
>> >> >> memory protection unit) and a distinction between user mode and
>> >> privileged
>> >> >> mode, which rules out many microcontrollers. About the implement of
>> >> >> HyperVisor for RTEMS there are two projects we can reference. First
>> is
>> >> project
>> >> >> XtratuM [3] which is a small
>> >> >> native (bare-metal) hypervisor, now the RTEMS has been ported to
>> >> XtratuM
>> >> >> run as a guest OS and its design use ARINC 653 as
>> >> >> a reference although ARINC-653 is not directly applicable to the
>> >> >> hypervisor systems. Another project is HelenOS operating
>> >> >> system [4] which is designed as a relatively small microkernel
>> assisted
>> >> >> with a set of userspace drivers and server tasks, Its kernel
>> >> >> is a good reference candidate for the design of Hypervisor.
>> >> >> This is just my initial thoughts, if there is any inappropriate
>> please
>> >> >> point out.Do not hesitate to add your comments.
>> >> >>
>> >> >> Wenjie Zhang
>> >> >> Best Regards
>> >> >>
>> >> >>
>> >> >>
>> >> >>
>> >> >
>> >> >--
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>> >
>
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