Change in coreboot[4.11_branch]: intel/stm: Place resource list right below MSEG

[Marc Jones (Code Review)]

Attention is currently required from: Eugene Myers.
Hello Eugene Myers,

I'd like you to do a code review. Please visit

https://review.coreboot.org/c/coreboot/+/50312

to review the following change.

Change subject: intel/stm: Place resource list right below MSEG
......................................................................

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 
Original-Reviewed-on: https://review.coreboot.org/c/coreboot/+/40437
Original-Reviewed-by: Nico Huber 
Original-Reviewed-by: Angel Pons 
Original-Tested-by: build bot (Jenkins)

(cherry picked from commit 076605bc92730553e9adae543713f0d356a94709)
Signed-off-by: Marc Jones

Change-Id: Ie62e2bdccd2d09084cc39a0f2fe32df236c08cd6
---
M src/cpu/x86/smm/smm_module_loader.c
M src/security/intel/stm/StmPlatformSmm.c
2 files changed, 8 insertions(+), 18 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/12/50312/1

diff --git a/src/cpu/x86/smm/smm_module_loader.c b/src/cpu/x86/smm/smm_module_loader.c
index 3ed20b7..19acea6 100644
--- a/src/cpu/x86/smm/smm_module_loader.c
+++ b/src/cpu/x86/smm/smm_module_loader.c
@@ -318,13 +318,13 @@
 /* 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 @@

/* 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 @@
    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 45db0e0..248ccc0 100644
--- a/src/security/intel/stm/StmPlatformSmm.c
+++ b/src/security/intel/stm/StmPlatformSmm.c
@@ -177,12 +177,7 @@

// 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);