Re: [Xen-users] xen version compatibility

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> > If I have a linux kernel on dom0 from xen 3.0.2 and my xen binary is
> > version 3.1.0, can I expect things to work?  What about if my dom0
> > kernel and xen binary are both 3.1.0 and I have a para virt domU with
> > xen 3.0.2 code in?  What about if the tools are from a different
> > version of xen?
>
> The HV <-> DomU  ABI is guarenteed to be stable for the lifetime of
> 3.x series of Xen releases. So a 3.0.2 guest should work on a 3.1.0
> hypervisor, and vica-verca.

Regarding domU guests:

Guests will potentially only be able to run on older hypervisors if they 
include appropriate compatibility code.  Some new interfaces have been added 
during the 3.0 series (e.g. the new SCHED_ops) which newer guests may be 
expecting...

The ABI itself only guarantees that older guests will run on newer Xens...  
Anything beyond that is up to the guest to implement.  The default compile 
option for Linux is to include legacy support for older hypervisors, so in 
practice, guests will generally run on older Xens.

Cheers,
Mark

> There may, however, be lesser capabilities 
> with certain combinations - for example if you want to run 32-on-64
> guests, you do need to have 3.1.0 Dom0 kernel due to backend driver
> changes.
>
> > I'm asking because I'm running fedora 6 and I'd like to try out xen
> > 3.1.0 or 3.0.4 but I don't want to have to manually compile all my
> > kernels all the time.
>
> That should work. We test running Fedora 7 (Xen 3.1.0) guests on a
> Fedora Core 6 dom0 (3.0.3), and also test FC6 guests on a Fedora 7
> Dom0. Any problems should be reported as bugs :-)
>
> Dan.



-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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