[M] Change in coreboot[master]: {cpu, security}: Stitch multiple microcodes per CPUID into CBFS

[Subrata Banik (Code Review)]

Attention is currently required from: Arthur Heymans, Himanshu Sahdev, Julius Werner, Lean Sheng Tan, Rizwan Qureshi, Tarun Tuli, Wonkyu Kim, Yu-Ping Wu.

Subrata Banik has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/75357?usp=email )

Change subject: {cpu, security}: Stitch multiple microcodes per CPUID into CBFS
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Patch Set 14:

(1 comment)

File src/cpu/Kconfig:

https://review.coreboot.org/c/coreboot/+/75357/comment/0fae1596_e9a96211 :
PS14, Line 216: config CPU_UCODE_SPLIT_BINARIES
              : 	string "Split microcode blob directory path"
              : 	depends on CPU_MICROCODE_CBFS_SPLIT_BINS
              : 	default ""
              : 	help
              : 	  Provide the microcode blob directory path based on the configuration setting that
              : 	  allows for split microcode binaries per CPUID for both RO and RW CBFS.
              : 
              : 	  Some platforms have microcode in the blobs directory, and these can be hardcoded
              : 	  in the makefiles. The expected format for keeping the microcode filename in the
              : 	  directory is `cpu_microcode_$(CPUID).bin`.
              : 
              : 	  This should contain the full path of the microcode blob directory. For example:
              : 	  "3rdparty/blobs/mainboard/$(CONFIG_MAINBOARD_DIR)/microcode_inputs".
              : 
              : 	  If unsure, leave this blank.
> Can the existing options not be reused? I don't see how fetching everything from a dir is related to splitting binaries in cbfs.

as mentioned I will add the proper descriptions about what this directory should hold. For sure there is no magic in the directory that can help to split the microcode. Rather the directory path to provide the split ucode source and I should provide more details about file name format.