RE: Guest-visible phys2mach part of Xen arch-neutral API? was:[Xen-devel] Uses of &frame_table[xfn]

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

> > Yes, that's the current status: No way to see underlying 
> > machine address in other domains and thus no way for driver domains. 

> Itanium cluster (~1000 nodes). I'm not sure if it would be possible to
> use Xen on the cluster without driver domains though. Just food for

Just to clarify: This doesn't say that there can't be driver domains.
Driver domains would need to be implemented p==m, same as domain0, except
they would need to be given a different EFI memory map.  They have
not been implemented on Xen/ia64 because they have not yet re-appeared
in Xen/x86.

But I am intrigued by your statement... are you assuming that
Xen and domain0 are both single-system-image across the 1000+
nodes?  I think one of the difficulties with implementing driver
domains is that Xen (in the hypervisor) needs to discover and
somehow partition all the devices.  This could be a real challenge
for huge clusters.

Thanks,
Dan

> -----Original Message-----
> From: Kevin Fox [mailto:Kevin.Fox@xxxxxxx] 
> Sent: Friday, December 30, 2005 9:35 AM
> To: Tian, Kevin
> Cc: Keir Fraser; Magenheimer, Dan (HP Labs Fort Collins); Xen 
> Mailing List
> Subject: RE: Guest-visible phys2mach part of Xen arch-neutral 
> API? was:[Xen-devel] Uses of &frame_table[xfn]
> 
> There has been some discussion about some day using Xen on our large
> Itanium cluster (~1000 nodes). I'm not sure if it would be possible to
> use Xen on the cluster without driver domains though. Just food for
> thought.
> 
> Kevin
> 
> PS. I'm fairly disappointed in the lack of focus that driver 
> domains are
> receiving in Xen. I use them on several machines (one in 
> production) and
> I think it counts among Xen's greatest features.
> 
> On Fri, 2005-12-30 at 10:16 +0800, Tian, Kevin wrote:
> > >From: Keir Fraser [mailto:Keir.Fraser@xxxxxxxxxxxx]
> > >Sent: 2005å12æ29æ 21:48
> > >
> > >
> > >On 29 Dec 2005, at 01:59, Tian, Kevin wrote:
> > >
> > >>  IMO, I see the phys2mach mapping as a basic 
> virtualization policy,
> > >> instead of an architecture specific requirement. After adding
> > >> phys2mach concept to XEN/IA64, we can reuse more common 
> code without
> > >> ifdef. Then correspondingly also need to add several 
> necessary changes
> > >> like x86: DMA, SWIOTLB, AGP, etc, to ensure legal machine address
> > >> written into physical devices.
> > >
> > >This seems to make sense to me. How does ia64/xen work right now?
> > >Machine addresses visible to domain0 and full virtualisation of
> > >addresses exposed to other domains (with no way of seeing 
> underlying
> > >machine addresses)?
> > >
> > >  -- Keir
> > 
> > Yes, that's the current status: No way to see underlying 
> machine address in other domains and thus no way for driver domains.
> > 
> > Thanks,
> > Kevin
> > 
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
> 

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