[XS] Change in coreboot[main]: [WIP]arch/x86/car.ld: Drop the mrc_var section

[Arthur Heymans (Code Review)]

Attention is currently required from: Jérémy Compostella.

Arthur Heymans has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/81449?usp=email )

Change subject: [WIP]arch/x86/car.ld: Drop the mrc_var section
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Patch Set 1: Code-Review-2

(1 comment)

Patchset:

PS1:
> I found one occurence where it might be indirectly used.
> #+caption: coreboot::src/northbridge/intel/sandybridge/raminit_mrc.c
> #+begin_src c -n 234
> #define DCACHE_RAM_MRC_VAR_BASE	 (CONFIG_DCACHE_RAM_BASE + CONFIG_DCACHE_RAM_SIZE \
>    			+ CONFIG_DCACHE_RAM_MRC_VAR_SIZE - 0x4000)
>
> #+end_src
> #+caption: coreboot::src/northbridge/intel/sandybridge/raminit_mrc.c
> #+begin_src c -n 416
>    /* Sanity check mrc_var location by verifying a known field */
>    mrc_var = (void *)DCACHE_RAM_MRC_VAR_BASE;
>    if (mrc_var->tx_byte == pei_data.tx_byte_ptr) {
>    	printk(BIOS_DEBUG, "MRC_VAR pool occupied [%08x,%08x]\n",
>    	       mrc_var->pool_base, mrc_var->pool_base + mrc_var->pool_used);
>
> #+end_src
>
> But I am still a bit puzzled by the way the math is done in this file I am not familiar with and curious why they don't access the region through its symbol

I think the code predates the elf section. The section was added to be able to unify CAR setup on all targets that support the non-evict MSR, to know how the MTRR needs to be set up. Now that I'm writing this, it's obvious that it's going to break those platforms ^^