Re: Xen 4.4 development update

[George Dunlap <george.dunlap@eu.citrix.com>]

On 15/08/13 14:24, Wei Liu wrote:
> On Thu, Aug 15, 2013 at 02:08:01PM +0100, Jan Beulich wrote:
>>>>> On 15.08.13 at 15:02, Wei Liu <wei.liu2@citrix.com> wrote:
>>> On Thu, Aug 08, 2013 at 05:09:35PM +0100, George Dunlap wrote:
>>>> * Remove hardcoded mobprobe's in xencommons
>>>>    owner: Wei Liu
>>>>    status: still in discussion
>>>>
>>> Have we not reached conclusion here? IIRC in a engineering meeting we
>>> had you said we could just leave it as-is for now?
>> ??? Didn't we long ago agree that this hard coded loading is bogus
>> and hence should go away? Remember this was originally planned
>> to happen for 4.3, so any change in direction here needs a very
>> good reason imo.
>>
> Actually I wasn't completely sure I remembered the right thing. I might
> be wrong about the conclusion.  Geroge, do you have any clue? :-)

I think the conclusion we came to was as follows:

* Calling modprobe from libxl is not really feasible due to the fact 
that we have to call exec, which means making some of the calls async; 
one thing led to another and a huge number of calls would have had to be 
made async.

* It is better if kernels use the auto-load mechanisms as much as 
possible, rather than modprobes either in the init scripts or from libxl

* However, blktap is unmaintained.  Unless someone steps up to add the 
functionality (which is not recommended as it would probably te a waste 
of effort), it will continue to require a modprobe. On newer systems, 
without blktap, the modprobe will be harmless.  So for blktap, the 
modprobe will have to remain for the forseeable future.

* It would be good if other modules were modified so that they were 
auto-loaded, rather than modprobed.  However, this was outside of the 
scope of the work I or Wei agreed to do.  We agreed to handle blktap, 
and the blktap module loading issue has been resolved.

* Modifying other modules is an open ticket item

Correct me if I'm wrong, anyone.

I can put "auto-load other modules" on the roadmap without an owner, if 
you like.

  -George