cpu/x86/: Centralize MSEG location calculation

This patch centralizes the MSEG location calculation. In the current
implementation, the calculation happens in smm_module_loader and
mp_init.  When smm_module_loaderv2 was added, this calculation became
broken as the original calculation made assumptions based on perm_smbase.

The calculation is now located in smm_subregion (tseg_region.c), as the
MSEG is located within the TSEG (or SMM);

These patches have been tested on a Purism librem-l1um server.

Change-Id: Ic17e1a505401c3b2a218826dffae6fe12a5c15c6
Signed-off-by: Eugene Myers <edmyers@tycho.nsa.gov>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55628
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/cpu/x86/mp_init.c

@@ -756,9 +756,9 @@ static void asmlinkage smm_do_relocation(void *arg)
 	if (CONFIG(STM)) {
 		if (is_smm_enabled()) {
 			uintptr_t mseg;
+			size_t mseg_size;
 
-			mseg = mp_state.perm_smbase +
+			smm_subregion(SMM_SUBREGION_MSEG, &mseg, &mseg_size);
-				(mp_state.perm_smsize - CONFIG_MSEG_SIZE);
 
 			stm_setup(mseg, p->cpu, runtime->num_cpus,
 					perm_smbase,

src/cpu/x86/smm/smm_module_loader.c

@@ -368,7 +368,7 @@ int smm_load_module(void *smram, size_t size, struct smm_loader_params *params)
 	base += size;
 
 	if (CONFIG(STM))
-		base -= CONFIG_MSEG_SIZE + CONFIG_BIOS_RESOURCE_LIST_SIZE;
+		base -= CONFIG_BIOS_RESOURCE_LIST_SIZE;
 
 	params->stack_top = base;
 

src/cpu/x86/smm/smm_module_loaderv2.c

@@ -586,8 +586,8 @@ int smm_load_module(void *smram, size_t size, struct smm_loader_params *params)
 
 	/* MSEG starts at the top of SMRAM and works down */
 	if (CONFIG(STM)) {
-		base -= CONFIG_MSEG_SIZE + CONFIG_BIOS_RESOURCE_LIST_SIZE;
+		base -= CONFIG_BIOS_RESOURCE_LIST_SIZE;
-		total_size += CONFIG_MSEG_SIZE + CONFIG_BIOS_RESOURCE_LIST_SIZE;
+		total_size += CONFIG_BIOS_RESOURCE_LIST_SIZE;
 	}
 
 	/* FXSAVE goes below MSEG */

src/cpu/x86/smm/tseg_region.c

@@ -17,6 +17,7 @@
 #include <cpu/x86/smm.h>
 #include <stage_cache.h>
 #include <types.h>
+#include <inttypes.h>
 
 /*
  *        Subregions within SMM
@@ -25,6 +26,8 @@
  *     +-------------------------+
  *     |  External Stage Cache   | SMM_RESERVED_SIZE
  *     +-------------------------+
+ *     |          STM            | MSEG_SIZE
+ *     +-------------------------+
  *     |      code and data      |
  *     |         (TSEG)          |
  *     +-------------------------+ TSEG
@@ -35,17 +38,24 @@ int smm_subregion(int sub, uintptr_t *start, size_t *size)
 	size_t sub_size;
 	const size_t ied_size = CONFIG_IED_REGION_SIZE;
 	const size_t cache_size = CONFIG_SMM_RESERVED_SIZE;
+	const size_t mseg_size = CONFIG_MSEG_SIZE;
 
 	smm_region(&sub_base, &sub_size);
 
 	ASSERT(IS_ALIGNED(sub_base, sub_size));
-	ASSERT(sub_size > (cache_size + ied_size));
+	ASSERT(sub_size > (cache_size + ied_size + mseg_size));
 
 	switch (sub) {
 	case SMM_SUBREGION_HANDLER:
 		/* Handler starts at the base of TSEG. */
 		sub_size -= ied_size;
 		sub_size -= cache_size;
+		sub_size -= mseg_size;
+		break;
+	case SMM_SUBREGION_MSEG:
+		/* MSEG follows the SMM HANDLER subregion */
+		sub_base += sub_size - (ied_size + cache_size + mseg_size);
+		sub_size = mseg_size;
 		break;
 	case SMM_SUBREGION_CACHE:
 		/* External cache is in the middle of TSEG. */
@@ -88,11 +98,11 @@ void smm_list_regions(void)
 		return;
 
 	printk(BIOS_DEBUG, "SMM Memory Map\n");
-	printk(BIOS_DEBUG, "SMRAM       : 0x%zx 0x%zx\n", base, size);
+	printk(BIOS_DEBUG, "SMRAM       : 0x%" PRIxPTR " 0x%zx\n", base, size);
 
 	for (i = 0; i < SMM_SUBREGION_NUM; i++) {
 		if (smm_subregion(i, &base, &size))
 			continue;
-		printk(BIOS_DEBUG, " Subregion %d: 0x%zx 0x%zx\n", i, base, size);
+		printk(BIOS_DEBUG, " Subregion %d: 0x%" PRIxPTR " 0x%zx\n", i, base, size);
 	}
 }

src/include/cpu/x86/smm.h

@@ -168,6 +168,8 @@ void smm_region(uintptr_t *start, size_t *size);
 enum {
 	/* SMM handler area. */
 	SMM_SUBREGION_HANDLER,
+	/* MSEG (STM). */
+	SMM_SUBREGION_MSEG,
 	/* SMM cache region. */
 	SMM_SUBREGION_CACHE,
 	/* Chipset specific area. */