Re: [Xen-devel] [PATCH RFC 0/5] Split off mini-os to a separate tree

[Anil Madhavapeddy <anil@xxxxxxxxxx>]

On 26 Jan 2015, at 18:21, Martin Lucina <martin@xxxxxxxxxx> wrote:
> 
> anil@xxxxxxxxxx said:
>> On 26 Jan 2015, at 17:42, Martin Lucina <martin@xxxxxxxxxx> wrote:
>>> 
>>> talex5@xxxxxxxxx said:
>>>> In case it's useful: for the standalone version of Mini-OS used by
>>>> Mirage, I had to include these directories too:
>>>> 
>>>> 1. xen/include/public
>>>> 2. xen/common/libfdt
>>>> 3. xen/include/xen/libfdt
>>>> 4. config
>>>> 
>>>> ( https://github.com/talex5/xen/tree/minios-releases )
>>> 
>>> Ah, so that's where the Mirage fork of Mini-OS lives. I knew there was one,
>>> but not where. Any other forks please speak up :-)
>>> 
>>> Which parts of Mini-OS does Mirage actually use? I know you have an OCaml
>>> implementation of netfront, for instance.
>> 
>> Not very much of Mini-OS -- Mirage has everything from the ring protocol
>> up (XenStore, NetBack/Front, BlkBack/Front, Console, etc are all in OCaml).
>> So event channels and start of day boot, mainly.
>> 
>> It is useful to have the C XenBus around for start-of-day logging though,
>> since the emergency console isn't much use on public cloud services.
> 
> Interesting. Rump Kernels on Xen currently use the Mini-OS xenbus,
> {net,blk,pci}front and console, however AFAICT most (all?) of these could
> be provided by the NetBSD drivers instead. Such a setup also would not
> leave much from Mini-OS.
> 
> I'm wondering if there is interest in a Nano-OS that provides just the bare
> minimum needed for Unikernels to run atop cloud hypervisors (hint hint)?

I think the current approach of just including the object files that are
needed by the implementation is fine.  It's just the start_kernel (weak)
symbol that needs to call the initialisers for each subsystem, and the other
object files are pretty standalone.  A few more #ifdefs could be sprinkled
around perhaps, but there's no need to break down MiniOS much more than it
already is.

-anil
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