** Description changed:
+ SRU Justification:
+
+ [Impact]
+ * L1 host hangs when triggering FADump with recommended 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
+ 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
+ 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
+ /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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https://bugs.launchpad.net/bugs/2060039
Title:
[Ubuntu-24.04] FADump with recommended crash size is making the L1
hang
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