Re: [Xen-devel] [PATCH] /sys/hypervisor/uuid

[Jeremy Katz <katzj@xxxxxxxxxx>]

On Mon, 2006-05-22 at 07:33 +0100, Keir Fraser wrote:
> On 22 May 2006, at 07:21, Markus Armbruster wrote:
> >> I'm personally not against the sysfs solution though, if we agree that
> >> seeing your own uuid is useful at all.
> > [...]
> >
> > How do we reach agreement (or conclude we don't)?  Do we still need
> > more or clearer arguments for seeing one's UUID?
> 
> That's one problem, since nothing in the Xen tree will be making use of 
> this new functionality.
> 
> The main argument seems to be about how this should be exposed to user 
> space. It seems reasonable to me to add this to sysfs given that we 
> already have a driver that exports even weirder stuff like compilation 
> info for Xen itself! OTOH there is absolutely no guarantee that the 
> xen_sysfs driver will get picked up by mainline -- there are plenty of 
> people who think that kind of info has no place in the guest kernel, 
> and they have a point. So xen_sysfs may be a dead end.

And accessing xenstore from the guest kernel may also be a dead end.
There are no guarantees until things get upstream which is why that is
so vitally important.  Then again, stability of sysfs/procfs isn't all
that existent in the kernel anyway, so those who use functionality there
are used to having to change it over time ;-)

> If we allowed unprivileged read access to xenstore, that would require 
> only a smaller and more general patch to the kernel. Then you could put 
> the uuid extraction logic in user space?

But if you still require xs transactions, then it remains complicated
and a potential way to introduce fun problems for dom0 from a domU.
Especially as I would expect that then people will start coding their
own stuff instead of bringing a dep on libxs into domUs

Jeremy


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