arch/x86/Kconfig: introduce RESERVED_PHYSICAL_ADDRESS_BITS_SUPPORT

Since also some AMD CPUs have reserved physical address bits that can't
be used as normal address bits, introduce the
RESERVED_PHYSICAL_ADDRESS_BITS_SUPPORT Kconfig option which gets
selected by CPU_INTEL_COMMON, and use the new common option to configure
if the specific SoC/CPU code implements get_reserved_phys_addr_bits or
if the default of this returning 0 is used instead.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: I0059e63a160e60ddee280635bba72d363deca7f7
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78073
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-by: Jérémy Compostella <jeremy.compostella@intel.com>
Reviewed-by: Matt DeVillier <matt.devillier@amd.corp-partner.google.com>

src/arch/x86/Kconfig

@@ -92,6 +92,16 @@ config ARCH_X86_64_PGTBL_LOC
 	  The position where to place pagetables. Needs to be known at
 	  compile time. Must not overlap other files in CBFS.
 
+config RESERVED_PHYSICAL_ADDRESS_BITS_SUPPORT
+	bool
+	help
+	  On some systems, the upper physical address bits are reserved and
+	  used as a tag which is typically related to a memory encryption
+	  feature. When selecting this option, the SoC code needs to implement
+	  get_reserved_phys_addr_bits so that the common code knows how many of
+	  the most significant physical address bits are reserved and can't be
+	  used as address bits.
+
 # This is an SMP option. It relates to starting up APs.
 # It is usually set in mainboard/*/Kconfig.
 # TODO: Improve description.

src/arch/x86/include/arch/cpu.h

@@ -316,7 +316,7 @@ size_t get_cache_size(const struct cpu_cache_info *info);
  */
 bool fill_cpu_cache_info(uint8_t level, struct cpu_cache_info *info);
 
-#if CONFIG(CPU_INTEL_COMMON)
+#if CONFIG(RESERVED_PHYSICAL_ADDRESS_BITS_SUPPORT)
 unsigned int get_reserved_phys_addr_bits(void);
 #else
 /* Default implementation */

src/cpu/intel/common/Kconfig

@@ -1,5 +1,6 @@
 config CPU_INTEL_COMMON
 	bool
+	select RESERVED_PHYSICAL_ADDRESS_BITS_SUPPORT
 
 if CPU_INTEL_COMMON