Xen users - Apr 2013 - A few technical questions

Hello all, I''ve been tinkering with Xen for a while, and a few
technical
questions came up that I have yet to find succinct answers for. If someone
has the time to answer these, it will certainly speed along my deployment :D
> Who owns the threads(proper term?) representing to the VCPUs? Is there
some way in which I can access those threads or control how they are
launched? I guess in general the process of loading a VM is a little fuzzy
to me. (do VMs go through the Dom0 kernel to do memory access or is that
handled completely by the hypervisor? Are the threads visible to Dom0?) In
general I''m wondering if there''s a way to launch a VM such
that all its
VCPUs are under a thread migration framework
> Virtual disk chaining, is it possible to make modifications to the disk
and have the changes be made to that image rather than chained on? (failing
that, is it possible to go back and consolidate identical blocks?) If
I''ve
understood it correctly, it''s copy-on-write, and any extra copies pull
from
the main image but write their changes to their own copy. This seems like a
very basic question, but I was unable to find explicitly whether or not
it''s possible to make updates to only the original copy. It seems like
this
should work, but since I''m here, couldn''t hurt to throw that
one in as well
> Graphics passthrough. I''ve read conflicting stories on this. Is it
possible to pass a host''s primary graphics adapter through to a guest,
and
have that guest output all graphics through it? In that case, it seems it
would require some functionality to switch the graphics adapter back. Would
this be handled by that VGPU mapping feature in XAPI? The motherboard I was
testing with lacked an IOMMU, so I was unable to test it properly. If
someone has a clear answer on this, it would be awesome

Thanks for your time,
Sean Pryor


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On 04/22/2013 01:56 AM, Sean Pryor wrote:
>  > Graphics passthrough. I''ve read conflicting stories on this.
Is it
> possible to pass a host''s primary graphics adapter through to a
guest,
> and have that guest output all graphics through it? In that case, it
> seems it would require some functionality to switch the graphics adapter
> back. Would this be handled by that VGPU mapping feature in XAPI? The
> motherboard I was testing with lacked an IOMMU, so I was unable to test
> it properly. If someone has a clear answer on this, it would be awesome
Considering I''ve spent the whole weekend getting secondary ATI GPU to 
work reliably when passed through to a guest VM, I wouldn''t hold much 
hope for less documented/supported features working usably well when it 
comes to VGA passthrough.

Gordan