Re: [Xen-devel] making xenstore domain easy configurable

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 28/06/16 14:52, Juergen Gross wrote:
> On 28/06/16 14:42, Andrew Cooper wrote:
>> On 28/06/16 12:56, Juergen Gross wrote:
>>> On 28/06/16 13:03, Ian Jackson wrote:
>>>> Juergen Gross writes ("Re: [Xen-devel] making xenstore domain easy 
>>>> configurable"):
>>>>> So you are telling me the xenstore domain won't work for this case?
>>>> Yes.
>>> That's rather unfortunate. So in order to be able to make xenstore
>>> domain a common setup we need to find a solution for support of
>>> xs_restrict() via xenbus, right?
>>>
>>> TBH, the way xs_restrict() was introduced is rather weird. It is
>>> completely bound to the socket interface of oxenstored. So anyone
>>> wanting to use xs_restrict() is limited to oxenstored running in
>>> dom0. No way to use xenstored or a xenstore domain. I'm really
>>> disappointed such a design was accepted and is now the reason for
>>> not being able to disaggregate dom0.
>>>
>>> I've searched through the xen-devel archives and found a very
>>> interesting mail:
>>>
>>> http://lists.xen.org/archives/html/xen-devel/2010-04/msg01318.html
>>>
>>> The "restrict" feature was added without any further discussion how
>>> it is implemented and that the C-variant doesn't support it. The
>>> explicit question about non-existing features in the C xenstored was
>>> answered just with "the xenstore wire protocol doesn't change".
>>>
>>> With:
>>>
>>> http://lists.xen.org/archives/html/xen-devel/2010-07/msg00091.html
>>>
>>> the XS_RESTRICT value in xs_wire.h (aah, suddenly it was changed?)
>>> was added. Again no mentioning of the special implementation in
>>> oxenstored.
>>>
>>> Really, this is not how open source development should be done!
>>> Maybe I'm just upset now, but I'm in favor of dropping xs_restrict()
>>> support as it has been introduced in a foul way.
>> I don't think the lack of xs_restrict() working over the ring should
>> preclude these improvements to the configuration of how xenstored starts up.
>>
>> Ideally, this issue would be listed in an appropriate place in
>> docs/features/, in the hope that it gets considered and addressed in the
>> future.
> Digging a little bit deeper I think the current xs_restrict()
> implementation renders an oxenstore domain completely useless: as
> soon as dom0 tries to use xs_restrict() it will loose its privileges
> as the complete dom0 connection will be affected. :-(

Can't say I am surprised in the slightest.  It is an extension which has
never been used, which invariably means it doesn't work.

(More replies on the other half of this thread, which I am still writing.)

~Andrew

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