intel/stm: Place resource list right below MSEG

Suggested by Nico Huber in CB:38765.

This placement makes the address calculation simpler and
makes its location indepedent of the number of CPUs.

As part of the change in the BIOS resource list address
calculation, the `size` variable was factored out of the
conditional in line 361, thus eliminating the else.

Original-Change-Id: I9ee2747474df02b0306530048bdec75e95413b5d
Original-Signed-off-by: Eugene D Myers <cedarhouse@comcast.net>
Original-Reviewed-on: https://review.coreboot.org/c/coreboot/+/40437
Original-Reviewed-by: Nico Huber <nico.h@gmx.de>
Original-Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Original-Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

(cherry picked from commit 076605bc92730553e9adae543713f0d356a94709)
Signed-off-by: Marc Jones <marcjones@sysproconsulting.com>

Change-Id: Ie62e2bdccd2d09084cc39a0f2fe32df236c08cd6
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50312
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Jay Talbott <JayTalbott@sysproconsulting.com>
Reviewed-by: Eugene Myers <cedarhouse1@comcast.net>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

2 files changed, 8 insertions, 18 deletions

diff --git a/src/cpu/x86/smm/smm_module_loader.c b/src/cpu/x86/smm/smm_module_loader.c
index 3ed20b70bd5c..19acea60d68b 100644
--- a/src/cpu/x86/smm/smm_module_loader.c
+++ b/src/cpu/x86/smm/smm_module_loader.c
@@ -318,13 +318,13 @@ int smm_setup_relocation_handler(struct smm_loader_params *params)
 /* The SMM module is placed within the provided region in the following
  * manner:
  * +-----------------+ <- smram + size
- * |    stacks       |
- * +-----------------+ <- smram + size - total_stack_size
- * |  fxsave area    |
- * +-----------------+ <- smram + size - total_stack_size - fxsave_size
  * | BIOS resource   |
  * | list (STM)      |
- * +-----------------+ <- .. - CONFIG_BIOS_RESOURCE_LIST_SIZE
+ * +-----------------+ <- smram + size - CONFIG_BIOS_RESOURCE_LIST_SIZE
+ * |    stacks       |
+ * +-----------------+ <- .. - total_stack_size
+ * |  fxsave area    |
+ * +-----------------+ <- .. - total_stack_size - fxsave_size
  * |      ...        |
  * +-----------------+ <- smram + handler_size + SMM_DEFAULT_SIZE
  * |    handler      |
@@ -365,11 +365,10 @@ int smm_load_module(void *smram, size_t size, struct smm_loader_params *params)
 
 	/* Stacks start at the top of the region. */
 	base = smram;
+	base += size;
 
 	if (CONFIG(STM))
-		base += size - CONFIG_MSEG_SIZE;     // take out the mseg
-	else
-		base += size;
+		base -= CONFIG_MSEG_SIZE + CONFIG_BIOS_RESOURCE_LIST_SIZE;
 
 	params->stack_top = base;
 
@@ -400,10 +399,6 @@ int smm_load_module(void *smram, size_t size, struct smm_loader_params *params)
 	total_size = total_stack_size + handler_size;
 	total_size += fxsave_size + SMM_DEFAULT_SIZE;
 
-	// account for the bios resource list
-	if (CONFIG(STM))
-		total_size += CONFIG_BIOS_RESOURCE_LIST_SIZE;
-
 	if (total_size > size)
 		return -1;
 
diff --git a/src/security/intel/stm/StmPlatformSmm.c b/src/security/intel/stm/StmPlatformSmm.c
index 45db0e069f14..248ccc028a91 100644
--- a/src/security/intel/stm/StmPlatformSmm.c
+++ b/src/security/intel/stm/StmPlatformSmm.c
@@ -177,12 +177,7 @@ void stm_setup(uintptr_t mseg, int cpu, int num_cpus, uintptr_t smbase,
 
 		// need to create the BIOS resource list once
 		// first calculate the location in SMRAM
-		addr_calc = (mseg - (CONFIG_SMM_MODULE_STACK_SIZE * num_cpus));
-
-		if (CONFIG(SSE))
-			addr_calc -= FXSAVE_SIZE * num_cpus;
-
-		addr_calc -= CONFIG_BIOS_RESOURCE_LIST_SIZE;
+		addr_calc = mseg - CONFIG_BIOS_RESOURCE_LIST_SIZE;
 		stm_resource_heap = (uint8_t *) addr_calc;
 		printk(BIOS_DEBUG, "STM: stm_resource_heap located at %p\n",
 				stm_resource_heap);