Select CONFIG_MICROCODE_LATE_LOADING

[pmenzel]

$ grep LATE_LOADI /boot/config-*
/boot/config-5.15.112.mx64.449:# CONFIG_MICROCODE_LATE_LOADING is not set
/boot/config-6.1.39.mx64.450:# CONFIG_MICROCODE_LATE_LOADING is not set
/boot/config-6.5.2.mx64.452:# CONFIG_MICROCODE_LATE_LOADING is not set

config MICROCODE_LATE_LOADING
        bool "Late microcode loading (DANGEROUS)"
        default n
        depends on MICROCODE
        help                                             
          Loading microcode late, when the system is up and executing instructions
          is a tricky business and should be avoided if possible. Just the sequence
          of synchronizing all cores and SMT threads is one fragile dance which does
          not guarantee that cores might not softlock after the loading. Therefore,
          use this at your own risk. Late loading taints the kernel too.

[pmenzel]

Allows to run:

# echo 1 > /sys/devices/system/cpu/microcode/reload

[pmenzel]

Commit a77a94f862 (x86/microcode: Default-disable late loading) introduced the Kconfig option, defaulting to no, so it was disabled in our systems as it was backported to Linux v5.15.99 (commit 6d2b3a319144f3f5148d8a2b19549ea3bb118c2e).

[donald]

Added to https://github.molgen.mpg.de/mariux64/linux/tree/linux-5.15.131-mpi
Added to https://github.molgen.mpg.de/mariux64/linux/commits/linux-6.5.2-mpi