[Bug 857662] Re: Should xenbus_probe_frontend be built-in?

[Launchpad Bug Tracker]

This bug was fixed in the package debian-installer - 20101020ubuntu77

---------------
debian-installer (20101020ubuntu77) precise; urgency=low

  * Bump powerpc netboot image size by a megabyte to allow for a slight
    kernel size increase.
  * Switch Xen images to the -virtual kernel flavour (LP: #857662).
 -- Colin Watson <cjwatson at ubuntu.com>   Sun, 20 Nov 2011 11:15:24 +0000

** Branch linked: lp:~ubuntu-core-dev/debian-installer/ubuntu

** Changed in: debian-installer (Ubuntu Precise)
       Status: Triaged => Fix Released

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https://bugs.launchpad.net/bugs/857662

Title:
  Should xenbus_probe_frontend be built-in?

Status in “debian-installer” package in Ubuntu:
  Fix Released
Status in “hw-detect” package in Ubuntu:
  Fix Released
Status in “linux” package in Ubuntu:
  Invalid
Status in “debian-installer” source package in Natty:
  Won't Fix
Status in “hw-detect” source package in Natty:
  Fix Released
Status in “linux” source package in Natty:
  Won't Fix
Status in “debian-installer” source package in Oneiric:
  Won't Fix
Status in “hw-detect” source package in Oneiric:
  Fix Released
Status in “linux” source package in Oneiric:
  Won't Fix
Status in “debian-installer” source package in Precise:
  Fix Released
Status in “hw-detect” source package in Precise:
  Invalid
Status in “linux” source package in Precise:
  Invalid

Bug description:
  Stable update justification:

  Impact: When installing in a Xen domU, the installer fails to find any network interfaces.
  Development branch: Fixed in hw-detect 1.81ubuntu3 by loading xenbus_probe_frontend if we seem to be running under the Xen hypervisor.  (It should not be catastrophic if we load this even under other conditions, but it should be a bit more efficient this way.)
  Patch: http://bazaar.launchpad.net/~ubuntu-core-dev/hw-detect/natty-proposed/revision/1466
  TEST CASE: Start up d-i in a Xen domU and run through to the point where it detects network interfaces.  Without this patch, it should fail; with this patch, it should work.  Note that for testing you will need to use a kernel/initrd from natty-proposed (which I'll need to upload separately after this patch is accepted), and in production after this upload is validated you'll need to use a kernel/initrd from natty-updates.
  Regression potential: I think the worst thing that can plausibly happen here is an error message via debconf if the module fails to load.  The /sys/hypervisor/type and /sys/bus/xen checks around this code are mainly to defend against this possibility in non-Xen installations.

  Original report follows:

  xenbus_probe_frontend is currently modular in several flavours,
  notably in the i386/generic-pae and amd64/generic flavours which we
  use to build d-i Xen netboot images.  The purpose of
  xenbus_probe_frontend appears to be to connect to the Xen bus and then
  emit uevents for any devices it finds there.  Once it's loaded,
  autoloading for such things as xen-netfront works fine, allowing the
  guest to find its network interface.  I believe that xen-blkfront
  works in a similar way.

  However, with xenbus_probe_frontend modular, the early stages of the
  installer plus the early stages of normal system boot need to load
  xenbus_probe_frontend in order to find block and network devices.  If
  we're going to do this, it seems as though we might as well just build
  xenbus_probe_frontend into the kernel.  It seems to me that it should
  be pretty harmless on non-Xen systems, although of course somebody
  knowledgeable should verify that.

  Right now, it's built in for the -virtual flavours, but we aren't
  currently building installer images from that, and I think I'm happier
  building them directly from -generic-pae / -generic anyway.

  This is true in both Natty and Oneiric.  If you can't do this for
  Oneiric and/or are unwilling to do this in a stable update for Natty,
  then please let me know so that I can add a workaround to the
  installer in time.  Thanks!

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