[Oneiric] Load xen_blkback and xen_netback on startup

Tested the following on 64bit Oneiric-server:

modules_setup()
{
        modprobe xenfs 2>/dev/null
        modprobe xen-evtchn 2>/dev/null
        modprobe xen_netback 2>/dev/null
        modprobe xen_blkback 2>/dev/null
}

Version: 4.1

For oneiric, this should be fixed in the xend init script in the xen-utils-common package, not in the xen-common package (I'm not sure what that is).

The ultimate fix is in the kernel, which should do this automatically. That's commit 149bb2fab547253e6359e76f1b86b95247110e68 in the kernel git tree. So an alternative fix for oneiric is to backport that. (Which may also involve backporting cc85e93342c030f8ba07f572afa159ec4518231f.)

I will see about getting this bug escalated. I think it should be fixed for oneiric and the fix is trivial and low-risk.

Dave Walker writes ("[Bug 803488] Re: [Oneiric] Load xen_blkback and xen_netback on startup"):
> ** Changed in: xen-common (Ubuntu Oneiric)
> Importance: Wishlist => Medium
>
> ** Changed in: xen-common (Ubuntu Oneiric)
> Assignee: (unassigned) => Dave Walker (davewalker)
>
> ** Changed in: xen-common (Ubuntu Oneiric)
> Milestone: None => ubuntu-11.10
>
> ** Tags added: server-o-rs

Thanks a lot!

Ian.

In theory having udev autoload them is better for sure. I would think that the bus triggering this would not be present if the kernel is not run as a dom0 kernel. Just something we want to make sure it really works before pushing out any changes to the kernel.

@Stefan, can you confirm that you have no concerns with them being modprobed for Oneiric target?

Thanks.

@Dave, can you confirm seeing my concerns in the previous comment? :-P Allright, allright, I will try what happens with those patches...

So doing a quick test by just removing my modprobe lines from the startup script and using a kernel in dom0 that has the two mentioned patches applied does _not_ work as is.
Basically the last patch just adds a new alias. But there needs to be a trigger requesting that. And that does not seem to happen. Now I did not spend an awful long time in looking where this should go. Feeling tends a bit into the time a domU with pv devices comes up. But right now, xm just hangs and xl has other issues apparently and complains about the kernel not being "right"...

So frankly I would just remain doing a modprobe in the init_script for Oneiric. And aim for something better to be with Pangolia...

Pangolin (wish the choice had been any animal one already knows...)

I think I was confused on what the proposed Oneiric resolution was. I thought it was being suggested that adding the two modprobes to the init script would be a suitable resolution.

Looking at the current archive package for modprobes it contains:
./debian/xen-utils-common.xend.init: modprobe xenfs 2>/dev/null
./debian/xen-utils-common.xend.init: modprobe xen-evtchn 2>/dev/null

Therefore the requirement is to add xen_blkback & xen_netback (and drop it for P-Series).

Have i miss-understood?

Thanks.

Right, that was my thinking. And accidentally I made that change manually for so long now, that _I_ was confused on the part of having it officially done or not. Or to be clear, I added the two additional modprobe lines to /etc/init.d/xend which I would think relates to the debian/xen-utils-common.xend.init.

Dave Walker writes ("[Bug 803488] Re: [Oneiric] Load xen_blkback and xen_netback on startup"):
> I think I was confused on what the proposed Oneiric resolution was. I
> thought it was being suggested that adding the two modprobes to the init
> script would be a suitable resolution.
>
> Looking at the current archive package for modprobes it contains:
> ./debian/xen-utils-common.xend.init: modprobe xenfs 2>/dev/null
> ./debian/xen-utils-common.xend.init: modprobe xen-evtchn 2>/dev/null
>
> Therefore the requirement is to add xen_blkback & xen_netback (and drop
> it for P-Series).

Yes, that was my understanding. I'm confident that this will be a
safe fix. It will only affect people who have xen-utils-common
installed, of course, and those people are presumably intending to run
Xen and do need those modules loaded.

Ian.

Having this modification done for a while now, I even can confirm that if you boot into the non-xen environment, none of the xen modules are loaded.

This bug was fixed in the package xen-common - 4.1.0~rc6-1ubuntu1

---------------
xen-common (4.1.0~rc6-1ubuntu1) oneiric; urgency=low

  * debian/xen-utils-common.xend.init: Added modprobe xen_blkback and
    xen_netback, as they are not automatically loaded with Oneiric.
    This can be dropped for 12.04 release. (LP: #803488)
 -- Dave Walker (Daviey) <email address hidden> Fri, 07 Oct 2011 18:47:50 +0100