soc/amd/common/block/cpu/noncar: add get_usable_physical_address_bits()

In case the secure memory encryption is enabled, some of the upper
usable address bits of the host can't be used any more. Bits 11..6 in
CPUID_EBX_MEM_ENCRYPT indicate how many of the address bits are taken
away from the usable address bits in the case the secure memory
encryption is enabled.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: Ia810b0984972216095da2ad8f9c19e37684f2a2e
Reviewed-on: https://review.coreboot.org/c/coreboot/+/75623
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/include/cpu/amd/cpuid.h

@@ -121,4 +121,8 @@
 #define  CPUID_EBX_THREADS_SHIFT	8
 #define  CPUID_EBX_THREADS_MASK		(0xff << CPUID_EBX_THREADS_SHIFT)
 
+#define CPUID_EBX_MEM_ENCRYPT		0x8000001f
+#define  CPUID_EBX_MEM_ENCRYPT_ADDR_BITS_SHIFT	6
+#define  CPUID_EBX_MEM_ENCRYPT_ADDR_BITS_MASK	(0x3f << CPUID_EBX_MEM_ENCRYPT_ADDR_BITS_SHIFT)
+
 #endif /* CPU_AMD_CPUID_H */

src/include/cpu/amd/mtrr.h

@@ -12,6 +12,7 @@
 #define MTRR_WRITE_MEM			(1 << 3)
 
 #define SYSCFG_MSR			0xC0010010
+#define SYSCFG_MSR_SMEE			(1 << 23)
 #define SYSCFG_MSR_TOM2WB		(1 << 22)
 #define SYSCFG_MSR_TOM2En		(1 << 21)
 #define SYSCFG_MSR_MtrrVarDramEn	(1 << 20)

src/soc/amd/common/block/cpu/noncar/cpu.c

@@ -1,9 +1,12 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
 #include <amdblocks/cpu.h>
+#include <arch/cpuid.h>
 #include <cpu/cpu.h>
 #include <cpu/x86/msr.h>
+#include <cpu/amd/cpuid.h>
 #include <cpu/amd/msr.h>
+#include <cpu/amd/mtrr.h>
 #include <smbios.h>
 #include <soc/iomap.h>
 #include <types.h>
@@ -31,3 +34,18 @@ void set_cstate_io_addr(void)
 	cst_addr.lo = ACPI_CSTATE_CONTROL;
 	wrmsr(MSR_CSTATE_ADDRESS, cst_addr);
 }
+
+static uint32_t get_smee_reserved_address_bits(void)
+{
+	if (rdmsr(SYSCFG_MSR).raw & SYSCFG_MSR_SMEE)
+		return (cpuid_ebx(CPUID_EBX_MEM_ENCRYPT) &
+			CPUID_EBX_MEM_ENCRYPT_ADDR_BITS_MASK) >>
+			CPUID_EBX_MEM_ENCRYPT_ADDR_BITS_SHIFT;
+	else
+		return 0;
+}
+
+uint32_t get_usable_physical_address_bits(void)
+{
+	return cpu_phys_address_size() - get_smee_reserved_address_bits();
+}

src/soc/amd/common/block/include/amdblocks/cpu.h

@@ -12,6 +12,7 @@ void early_cache_setup(void);
 int get_cpu_count(void);
 unsigned int get_threads_per_core(void);
 void set_cstate_io_addr(void);
+uint32_t get_usable_physical_address_bits(void);
 void write_resume_eip(void);
 
 union pstate_msr; /* proper definition is in soc/msr.h */