This bug is awaiting verification that the linux-xilinx/6.8.0-1009.10
kernel in -proposed solves the problem. Please test the kernel and
update this bug with the results. If the problem is solved, change the
tag 'verification-needed-noble-linux-xilinx' to 'verification-done-
noble-linux-xilinx'. If the problem still exists, change the tag
'verification-needed-noble-linux-xilinx' to 'verification-failed-noble-
linux-xilinx'.


If verification is not done by 5 working days from today, this fix will
be dropped from the source code, and this bug will be closed.


See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how
to enable and use -proposed. Thank you!


** Tags added: kernel-spammed-noble-linux-xilinx-v2 
verification-needed-noble-linux-xilinx

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https://bugs.launchpad.net/bugs/2060039

Title:
  [Ubuntu-24.04] FADump with recommended crash size is making the L1
  hang

Status in The Ubuntu-power-systems project:
  Fix Committed
Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Noble:
  Fix Committed
Status in linux source package in Oracular:
  Fix Released

Bug description:
  SRU Justification:

  [Impact]
   * L1 host hangs when triggering FADump that results in crash

  [Fix]
   * 353d7a84c214f184d5a6b62acdec8b4424159b7c 353d7a84c214 
"powerpc/64s/radix/kfence: map __kfence_pool at page granularity"

  [Test Case]
   * Have a Ubuntu Server 24.04 LTS installation on ppc64el.
   * Enable FADump with 1GB: fadump=on crashkernel=1024M
   * A kernel panic will happen when dump got triggered

  [Regression Potential]
  * There is a certain risk of a regression, but it is mapping only the memory
    allocated for KFENCE pool at page granularity, reducing memory consumption
    when KFENCE is used.

  * On top the commit is already upstream reviewed and accepted.

  * The modifications were done and tested by IBM.

  * The fadump feature is supported only on IBM POWER systems.

  [Other]
  * The fix/commit got upstream accepted with kernel v6.11-rc4,
    hence Oracular (with a planned kernel of 6.11) is not affected.

  .......................

  Problem description :
  ======================

  Triggered FADump with the recommended crash. L1 host got hung.

  As per the public document
  https://wiki.ubuntu.com/ppc64el/Recommendations recommended crash
  kernel size is 1024M for the system. But with 1024M and 2048M, the L1
  is getting hanged. with 4096, crash is generated and collected.

  root@ubuntu2404:~# uname -ar
  Linux ubuntu2404 6.8.0-11-generic #11-Ubuntu SMP Wed Feb 14 00:33:03 UTC 2024 
ppc64le ppc64le ppc64le GNU/Linux

  root@ubuntu2404:~# free -h
                 total        used        free      shared  buff/cache   
available
  Mem:            48Gi       1.7Gi        46Gi        13Mi       687Mi        
46Gi
  Swap:          8.0Gi          0B       8.0Gi

  root@ubuntu2404:~# cat /proc/cmdline
  BOOT_IMAGE=/vmlinux-6.8.0-11-generic root=/dev/mapper/ubuntu--vg-ubuntu--lv 
ro fadump=on crashkernel=1024M

  root@ubuntu2404:~# dmesg | grep -i reser
  [    0.000000] fadump: Reserved 1024MB of memory at 0x00000040000000 (System 
RAM: 51200MB)
  [    0.000000] fadump: Initialized 0x40000000 bytes cma area at 1024MB from 
0x40070000 bytes of memory reserved for firmware-assisted dump
  [    0.000000] Memory: 49316672K/52428800K available (23616K kernel code, 
4096K rwdata, 25536K rodata, 8832K init, 2487K bss, 2063552K reserved, 1048576K 
cma-reserved)
  [    0.396408] ibmvscsi 30000066: Client reserve enabled

  root@ubuntu2404:~# kdump-config show
  DUMP_MODE:            fadump
  USE_KDUMP:            1
  KDUMP_COREDIR:                /var/crash
     /var/lib/kdump/vmlinuz
  kdump initrd:
     /var/lib/kdump/initrd.img
  current state:    ready to fadump

  IBM is looking to update the crash kernel reservations section of the
  wiki for Power.

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