Re: [MirageOS-devel] MirageOS KVM Development

[Jon Ludlam <jjl25@xxxxxxxxx>]

On 19/08/14 14:58, Anil Madhavapeddy wrote:
> On 19 Aug 2014, at 08:54, Bill Gercken <bgercken@xxxxxxxxx> wrote:
>
>> Hello,
>>  
>> Is anybody actively working on support for KVM?
>>  
>> We are in a situation where we need to deploy to both Xen and KVM and I 
>> would love to be able to create unikernel applications that can be compiled 
>> for both environments.
>>
> KVM is not specifically being worked on at this time, but we'd love to hear 
> from anyone that would like to contribute towards the effort.  There have 
> been several recent developments to make this easier in Mirage 2:
>
> - the MiniOS library is now picked up from an external package
> - this library is in sync with the Xen development tree (should be part of 
> Xen 4.5) and is multiarch (x86_64/x86_32 and ARM).
> - TODO: add a HVM boot mode to upstream MiniOS to let it boot in Xen hardware 
> virt mode (Jon Ludlam had some patches against an earlier MiniOS that did 
> this).

Mostly what I did was forward-port some earlier patches by Dave Scott.
The branch is here: https://github.com/jonludlam/mirage-platform/tree/hvm.

What we did back then was use Pure64 to bootstrap, which leaves you in
an environment all set up, so we just skipped out some of the mini-os
setup. I now think it would be much better to do a full-on multiboot
compliant kernel. I suspect it's actually relatively straightforward for
Xen, since all we really need to do is set up the memory map (parsing
e820 & co.) - I don't think we need to worry about interrupts (I think)
as that can all be done via 'block domain' calls as we do with PV (as
hvmloader does). For KVM you'd presumably need to do a bit more with the
IDTs and making interrupt routines and whatnot.

Having said that, it'd be really nice to do the interrupts stuff;
writing some nice type-safe PCI drivers would be fun :-)

Jon


> After this, KVM support is pretty easy; it just needs the addition of virtio 
> drivers in OCaml, which isn't a complex task.
>
> -anil
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