Re: [Xen-devel] Xen on POWER

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 09/03/2018 09:37, awokd wrote:
> Specifically https://en.wikipedia.org/wiki/POWER9.
>
> Qubes user here. Due to the ongoing manufacturer lock-down of the x86
> arch. and security vulnerabilities introduced by same, I'm looking into
> hardware alternatives. One promising candidate appears to be the POWER
> architecture.
>
> What would it take to port Xen to the POWER9? In other words, if I wanted
> to do it, what would I be getting myself into? Apologies if this has been
> asked and answered or if I'm goring any oxen; my searches are coming up
> dry.

There have been various inquires on IRC, but I believe you're the first
to ask in this forum.

Xen currently has x86 and ARM as supported architectures, so there is a
reasonable split between common and arch-specific code.  As a start,
you'd need to implement enough of the arch stubs to make Power9 build,
then work on trying to get it to boot.

As a guess, the ARM port is going to be far closer to what you're
looking to do than the x86 side.

> It looks like KVM works on POWER. Could I look to see what had to be
> touched to support Xen on ARM and expect any changes would likely be in
> the same areas?

If KVM works, then yes, it will be the same kind of areas.

> If I do succeed in porting it, how much ongoing maintenance would be 
> necessary?

Porting is one thing, but as you identify below, not  letting it wither
is very different.  I can't predict how much ongoing maintenance would
be required, but it certainly can't be left alone once "complete".

> Lastly, along the lines of those who fail to learn from history are doomed
> to repeat it, what happened to the Xen PPC port a decade ago? I found an
> archive of the xen-ppc-devel mailing list but don't see any drama; seems
> like it just withered of its own accord.

That's what happens to things which don't get upstream.

There is certainly some interest in getting Power work, and the touted
system benefits are clear to see, but porting Xen and maintaining the
port is not going to be a trivial task.  If you are up for the
challenge, then I think it would a great opportunity.

~Andrew

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