cpu/intel/p4-netburst: skip caching rom on model_fxx

An unidentified combination of speculative reads and branch
predictions inside WRPROT-cacheable memory can cause invalidation of
cachelines and loss of stack on models based on NetBurst

Therefore disable WRPROT region entirely for all family F models.

As an extreme example, just changing the location of a constant string
passed to printk() has been witnessed to make a the boot fail early on
in romstage.

Change-Id: I1df84ad55e2d8d6d4e8dca10125131b5f525f0d7
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/27133
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
1 file changed