[coreboot-gerrit] Change in coreboot[master]: soc/intel/basecode: Add support for updating ucode loaded via FIT

[Arthur Heymans (Code Review)]

Arthur Heymans has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/27369 )

Change subject: soc/intel/basecode: Add support for updating ucode loaded via FIT
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Patch Set 47:

(2 comments)

https://review.coreboot.org/c/coreboot/+/27369/47/Documentation/soc/intel/uc... 
File Documentation/soc/intel/ucode_update/microcode_update_model.md:

https://review.coreboot.org/c/coreboot/+/27369/47/Documentation/soc/intel/uc... 
PS47, Line 1: # Microcode update mechanism for devices in field
The limitations should also be documented. Care should be taken on systems with socketed CPU's as replacing the CPU might end up with a non-booting system (if it needs a different MCU).

https://review.coreboot.org/c/coreboot/+/27369/47/src/soc/intel/common/basec... 
File src/soc/intel/common/basecode/fw_update/ucode_update.c:

https://review.coreboot.org/c/coreboot/+/27369/47/src/soc/intel/common/basec... 
PS47, Line 144: intel_microcode_find
This will result in a pointer to the microcode needed for the particular CPU you are using. This will cause problems on systems that have a socketed CPU as you may end up needing a different microcode when swapping CPU's.

The proper solution is to have multiple MCU FIT entries point a fixed offsets in that MCU update FMAP, while make sure there is enough place between them (since the sizes of the MCU are variable)