RE: [Xen-devel] [PATCH] VM-Tool: C-based Xen management tools

["Neugebauer, Rolf" <rolf.neugebauer@xxxxxxxxx>]

> -----Original Message-----
> From: xen-devel-admin@xxxxxxxxxxxxxxxxxxxxx [mailto:xen-devel-
> admin@xxxxxxxxxxxxxxxxxxxxx] On Behalf Of Mark Williamson
> Sent: 14 February 2005 16:36
> To: Anthony Liguori
> Cc: Mark Williamson; xen-devel@xxxxxxxxxxxxxxxxxxxxx; Nivedita Singhvi
> Subject: Re: [Xen-devel] [PATCH] VM-Tool: C-based Xen management tools
> 
> > Yes, PCI wouldn't be too hard to abstract.  Abstracting USB worries
me a
> > bit though.  On the one hand, you want to abstract at the device
level.
> 
> That would be a neat feature.  It'd require changes to the backend
device
> driver to be a bit smarter about grabbing devices, as well as frontend
> changes to communicate device identities the backend...
> 
> > It's even hairer with virtualization though.  Say you had two
harddrives
> > that were USB and not uniquely identifiable.  You want to assign
each
> > harddrive to a separate VM.  If you unplug them and swap ports, and
> > you're using the old configurations, you really want that each VM to
see
> > the harddrive they previously saw.  Swapping them could lead to
> > confusion and even worse, security problems.
> 
> The current implementation sidesteps all these by specifying port IDs.
> e.g.
> port 1 on my root hub always belongs to VM1 (when running), port 2 on
hub
> 3
> always belongs to VM2 (when running), etc.

A while back we were also discussing this to be the basic mechanism,
i.e. the level the exporting of USB devices work on. Then one could
implement higher level 'policies' in say dom0. for example one could
specify that if device of type foo gets plugged in then VM bar gets
granted access to that port. USB hotplugging should be able to do most
of the hard work...

rolf

> > Not sure the best solution here.  One of the reasons I've held off
on
> USB.
> 
> For comparison, do you know what abstraction other systems do?  Do
they
> assign
> ports or associate devices with VMs?
> 
> The latter is definitely an attractive option...  If we added support
for
> both
> ways of doing things, paranoid people (or people with weird devices!)
> could
> use the port specifiers, whilst others used device IDs.
> 
> What do you think?
> 
> Cheers,
> Mark
> 
> 
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