Re: [PATCH] xen: core dom0 support

From: Gerd Hoffmann
Date: Mon Mar 02 2009 - 04:32:55 EST


Ingo Molnar wrote:
>>> In three years time, will we regret having merged this?
>> Its a pretty minor amount of extra stuff on top of what's been
>> added over the last 3 years, so I don't think it's going to
>> tip the scales on its own. I wouldn't be comfortable in
>> trying to merge something that's very intrusive.
>
> Hm, how can the same code that you call "massive out-of-tree
> patches which doesn't make anyone happy" in an out of tree
> context suddenly become non-intrusive "minor amount of extra
> stuff" in an upstream context?

The current, out-of-tree xen kernel stuff is based on 2.6.18. That
predates pv_ops and is quite intrusive stuff, with alot of cut+paste
programming and dirty hacks.

Alot has happened in x86 land since 2.6.18. Being one of the x86 arch
maintainers you should know that very well. Most notably:

* pv_ops. Point of adding these is to allow virtualization-friendly
kernels *without* being intrusive as hell.
* x86 arch merge, followed up by tons of cleanups and code
reorganizations. These changes also make it easier to merge xen
support in a non-intrusive manner.

Also the xen support code in the linux kernel itself is basically a
rewrite from scratch, it hasn't much in common with the 2.6.18 code base.

> I wish the upstream kernel was able to do such magic, but i'm
> afraid it is not.

It's no magic, it's alot of hard work.

cheers,
Gerd


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/