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[Xen-devel] Merge Xen (the hypervisor) into Linux 
| To: | Steven Rostedt <rostedt@xxxxxxxxxxx> |  
| Subject: | [Xen-devel] Merge Xen (the hypervisor) into Linux |  
| From: | Ingo Molnar <mingo@xxxxxxx> |  
| Date: | Wed, 3 Jun 2009 01:28:43 +0200 |  
| Cc: | "npiggin@xxxxxxx" <npiggin@xxxxxxx>, "jeremy@xxxxxxxx" <jeremy@xxxxxxxx>,	"xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>,	"wimcoekaerts@xxxxxxxxxxxx" <wimcoekaerts@xxxxxxxxxxxx>,	"gregkh@xxxxxxx" <gregkh@xxxxxxx>,	George Dunlap <george.dunlap@xxxxxxxxxxxxx>,	"kurt.hackel@xxxxxxxxxx" <kurt.hackel@xxxxxxxxxx>,	"x86@xxxxxxxxxx" <x86@xxxxxxxxxx>,	Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>,	"linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>,	"xen-users@xxxxxxxxxxxxxxxxxxx" <xen-users@xxxxxxxxxxxxxxxxxxx>,	Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>,	Stephen Spector <stephen.spector@xxxxxxxxxx>,	"avi@xxxxxxxxxx" <avi@xxxxxxxxxx>,	"EAnderson@xxxxxxxxxx" <EAnderson@xxxxxxxxxx>,	"jens.axboe@xxxxxxxxxx" <jens.axboe@xxxxxxxxxx>,	ksrinivasan <ksrinivasan@xxxxxxxxxx>,	"torvalds@xxxxxxxxxxxxxxxxxxxx" <torvalds@xxxxxxxxxxxxxxxxxxxx>,	David Miller <davem@xxxxxxxxxxxxx>, Keir Fraser <Keir.Fraser@xxxxxxxxxxxxx> |  
| Delivery-date: | Thu, 04 Jun 2009 02:41:52 -0700 |  
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* Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> Now here's a crazy solution. Merge the Xen hypervisor into Linux 
> ;-)
That's not that crazy - it's the right technical solution if DOM0 is 
desired for upstream. From what i've seen in DOM0 land the incestous 
dependencies are really only long-term manageable if the whole thing 
is in a single tree.
A lot of Xen legacies could be dropped: the crazy ring1 hack on 
32-bit, the various wide interfaces to make pure-software 
virtualization limp along. All major CPUs shipped with hardware 
virtualization support in the past 2-3 years, so the availability of 
VMX and SVM can be taken for granted for such a project.
That cuts down on a fair amount of crap. A lot of code on the Linux 
side could be reused, and a pure CONFIG_PCI=y (all other things 
disabled) would provide a "slim hypervisor" instance with a very 
small and concentrated code base. (That 'slim hypervisor' might even 
be built with CONFIG_NOMMU.)
That way dom0 would be a natural extension: a minimal interface 
between Linux-Xen-minimal and the dom0 guest instance.
It's a sane technical model IMO, and makes dom0 a lot more 
palatable. Having in-tree competition to KVM would also obviously be 
good to Linux in general.
        Ingo
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