[SRU][J][PATCH 0/1] Kernel oops while removing device from cio_ignore list (LP: 1980951)

[frank.heimes at canonical.com]

BugLink: https://bugs.launchpad.net/bugs/1980951

SRU Justification:

[Impact] 

 * A kernel Oops occurs when a device is removed from the cio_ignore list
   (that is used to hide ccw devices) on a system with non-I/O subchannels
   (e.g. SCM or CHSC subchannels).

 * As a result, previously ignored devices cannot be activated again,
   and new devices cannot be found.

[Fix]

 * 0c3812c347bf 0c3812c347bfb0dc213556a195e79850c55702f5 "s390/cio: derive cdev information only for IO-subchannels"

[Test Plan]

 * An IBM zSystems or LinuxONE LPAR with with non-I/O subchannels.

 * Ubuntu Server 22.04 LTS (with GA kernel 5.15) installed.

 * Define a cio_ignore list (to hide ccw devices).

 * Remove a device from the cio_ignore list.

 * Due to hardware requirements this test needs to be conducted by IBM.

[Where problems could occur]

 * General problems may occur with ccw device activation/deactivation
   in case the new initialization is erroneous.

 * Issues may also have an impact on the type of ccw devices,
   and may no longer be limited to non-I/O subchannels.

 * Things could still go wrong in case cdev is still not properly
   derived from sch-type SUBCHANNEL_TYPE_IO.

[Other Info]
 
 * The commit is upstream since kernel 5.16 (next-20220315).

Vineeth Vijayan (1):
  s390/cio: derive cdev information only for IO-subchannels

 drivers/s390/cio/css.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

-- 
2.25.1