[Bug 1892367] Comment bridged from LTC Bugzilla

bugproxy 1892367 at bugs.launchpad.net
Mon Mar 29 12:10:06 UTC 2021 

------- Comment From heinz-werner_seeck at de.ibm.com 2021-03-29 08:04 EDT-------
Looks like an updated version of "s390-tools-signed" with the same version number than the normal s390-tools is needed for verification.

# sudo apt-get install s390-tools/focal-proposed
Reading package lists... Done
Building dependency tree
Reading state information... Done
Selected version '2.12.0-0ubuntu3.3' (Ubuntu:20.04/focal-proposed [s390x]) for 's390-tools'
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
s390-tools : Depends: s390-tools-signed (= 2.12.0-0ubuntu3.3) but 2.12.0-0ubuntu3.2 is to be installed
E: Unable to correct problems, you have held broken packages.

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https://bugs.launchpad.net/bugs/1892367

Title:
  [UBUNTU 20.04] udev rule change did not get applied

Status in Ubuntu on IBM z Systems:
  Fix Committed
Status in s390-tools package in Ubuntu:
  Fix Released
Status in s390-tools source package in Focal:
  Fix Committed
Status in s390-tools source package in Groovy:
  Fix Committed
Status in s390-tools source package in Hirsute:
  Fix Released

Bug description:
  SRU:
  ====

  [Impact]

   * In case a ccw (special s390x hardware) device is configured
     in a special (non-default) way using chzdev
     (like for example increasing the qeth buffer_count to 128),
     the modifications are not persistent by default, since the
     generated udev rules are not automatically incuded/added to the initramfs.

   * One needs to either manually re-create the initramfs,
     e.g. with 'sudo update-initramfs -k all -u' (maybe triggered by zipl)

   * or pass the arguments '-p -r zdev:early' to chzdev.

   * This is not really intuitive and what people expect
     and partly leads to confusion.

   * The solution is to compile with the ZDEV_ALWAYS_UPDATE_INITRD=1 option set.
     This makes sure that executions of chzdev always trigger 'update-initramfs -u'.

  [Test Plan]

   * Prepare an Ubuntu Server 20.04 or 20.04 on IBM Z with at least
     one ccw device, for example a qeth network device, here '0.0.1234'.
     (better to do that with a second spare qeth device,
      other than the one that is in use by your remote connection).

   * Configure the device using:
     sudo chzdev qeth -e 1234

   * Check the (default) value of a certain attribute, like qeth buffer_count:
     cat /sys/devices/qeth/0.0.1234/buffer_count
     64

   * Disable the ccw device again:
     sudo chzdev qeth -d 1234
     
   * And enable (re-)enable it with an increased buffer_count:
     sudo chzdev -e 1234 buffer_count=128

   * Check the (increased) value of the qeth buffer_count:
     cat /sys/devices/qeth/0.0.1234/buffer_count
     128

   * Restart the system (without manually running update-initramfs or zipl):
     sudo shutdown -r now

   * Once the system is up again, re-check if the ccw device was enabled again
     and if it still has the increased buffer_count value:
     lszdev qeth 1234
     TYPE  ID                          ON   PERS  NAMES
     qeth  0.0.1234:0.0.1235:0.0.1236  yes  yes   enc1234
     cat /sys/devices/qeth/0.0.1234/buffer_count
     128
     (alternatively check with: lsqeth enc1234 | grep buffer_count)

  [Where problems could occur]

   * The logic of handling DZDEV_ALWAYS_UPDATE_INITRD could be wrong, e.g. inversed.
     Then the initramfs is re-build even if not desired
     and in case needed not done, hence similar result than before.

   * The setting of 'ZDEV_ALWAYS_UPDATE_INITRD=1' could have been missed,
     which would lead to the similar behaviour than w/o the patch.

   * 'add_pers_removed' could handle wrong device types or not all devices,
     in case of potential array index errors.

   * 'is_zdev_early_0' could identify wrong persistent devices as some to be
     included early in the boot process (means added to the initramfs).

   * Problems in 'if (all_pers)' could lead to a wrong set of persistent devices
     that are considered (or not all),
     which could lead to unexpected (de-)configurations.

   * Finally the handling of the confirmation
     or the 'build of the command line' could be errornous,
     since the encapsulated if condition(s) changed (sightly).

  [Other Info]

   * This patch became upstream accepted with s390-tools 2.16.0 and is
     with that already included in hirsute, based on LP:1914574.

  __________

  During the ubuntu installation in tessia, we do chzdev for both dasd
  and qeth devices, as below.

  2020-08-20 09:54:45 | INFO | START subiquity/Early/run/command_1 : chzdev -e dasd 385c
  2020-08-20 09:54:45 | INFO | SUCCESS subiquity/Early/run/command_1 : chzdev -e dasd 385c
  2020-08-20 09:54:45 | INFO | START subiquity/Early/run/command_2 : chzdev -e qeth 0.0.bdf0
  2020-08-20 09:54:47 | INFO | SUCCESS subiquity/Early/run/command_2 : chzdev -e qeth 0.0.bdf0

  and we can see the below files in the /etc/udev/rules.d/
  oot at m8360024:~# ls -l /etc/udev/rules.d/
  total 76
  -rw-r--r-- 1 root root   154 Aug 20 09:08 41-cio-ignore.rules
  -rw-r--r-- 1 root root   430 Aug 20 09:08 41-dasd-eckd-0.0.385c.rules
  -rw-r--r-- 1 root root   357 Aug 20 09:08 41-generic-ccw-0.0.0009.rules
  -rw-r--r-- 1 root root  1049 Aug 20 09:08 41-qeth-0.0.bdf0.rules
  -rw-r--r-- 1 root root 58549 Aug 20 09:10 70-snap.snapd.rules

  Now, lsinitramfs shows files as below,

  root at m8360024:~# lsinitramfs /boot/initrd.img-5.4.0-42-generic | grep 41
  etc/udev/rules.d/41-cio-ignore-root.rules
  etc/udev/rules.d/41-dasd-eckd-0.0.385c.rules
  usr/lib/udev/rules.d/41-cio-ignore.rules
  usr/lib/udev/rules.d/41-dasd-eckd-0.0.385c.rules
  usr/lib/udev/rules.d/41-generic-ccw-0.0.0009.rules
  usr/lib/udev/rules.d/41-qeth-0.0.bdf0.rules

  Even though lsinitramfs shows the below files, they are overruled by
  the filesystem files.

  Next thing we did was to modify the 41-qeth-0.0.bdf0.rules and
  modified the buffer_count to 128 (As in the attached file). In ideal
  scenario, the value should we modified as mentioned in the bug. But,
  in our case, if we are not doing a zipl or update-initramfs -u, the
  value is not getting modified.

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