[S] Change in coreboot[main]: cpu/x86/smm: Fix get_save_state calculation

[Jérémy Compostella (Code Review)]

Attention is currently required from: EliasOfWaffle, Eugene Myers, Martin L Roth, Matt DeVillier, Michał Żygowski, Paul Menzel, Stefan Reinauer.

Jérémy Compostella has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/78889?usp=email )

Change subject: cpu/x86/smm: Fix get_save_state calculation
......................................................................

Patch Set 5:

(1 comment)

File src/cpu/x86/smm/smm_module_handler.c:

https://review.coreboot.org/c/coreboot/+/78889/comment/5e6256ba_9e837db9 :
PS4, Line 110: 		stm_psd_size = ALIGN_UP(sizeof(TXT_PROCESSOR_SMM_DESCRIPTOR),
> The inconsistency is in the definition of smm_runtime. […]

I am talking about a huge change. Just sharing definition. Here is what I have in mind.

```
Author:     Jeremy Compostella 
AuthorDate: Thu Nov 2 13:55:24 2023 -0700
Commit:     Jeremy Compostella 
CommitDate: Thu Nov 2 13:59:04 2023 -0700

cpu/x86/smm: Define STM descriptor size in SMM save state

Change-Id: Id68f9e650be24dd4d96788d2eeaea3dd88c26bd3
Signed-off-by: Jeremy Compostella

3 files changed, 11 insertions(+), 12 deletions(-)
src/cpu/x86/mp_init.c                | 5 +----
src/cpu/x86/smm/smm_module_handler.c | 9 +--------
src/include/cpu/x86/smm.h            | 9 +++++++++

modified   src/cpu/x86/mp_init.c
@@ -1087,10 +1087,7 @@ static void fill_mp_state_smm(struct mp_state *state, const struct mp_ops *ops)
    /*
     * Make sure there is enough room for the SMM descriptor
     */
-	if (CONFIG(STM)) {
-		state->smm_save_state_size +=
-			ALIGN_UP(sizeof(TXT_PROCESSOR_SMM_DESCRIPTOR), 0x100);
-	}
+	state->smm_save_state_size += STM_PSD_SIZE;

/*
     * Default to smm_initiate_relocation() if trigger callback isn't
modified   src/cpu/x86/smm/smm_module_handler.c
@@ -101,18 +101,11 @@ struct global_nvs *gnvs;

void *smm_get_save_state(int cpu)
 {
-	size_t stm_psd_size = 0;
-
    if (cpu > smm_runtime.num_cpus)
    	return NULL;

-	if (CONFIG(STM)) {
-		stm_psd_size = ALIGN_UP(sizeof(TXT_PROCESSOR_SMM_DESCRIPTOR),
-					0x100);
-	}
-
    return (void *)(smm_runtime.save_state_top[cpu] -
-			(smm_runtime.save_state_size - stm_psd_size));
+			(smm_runtime.save_state_size - STM_PSD_SIZE));
 }

uint32_t smm_revision(void)
modified   src/include/cpu/x86/smm.h
@@ -33,6 +33,15 @@

#define SMM_PCI_RESOURCE_STORE_NUM_RESOURCES 6

+/*
+ * SMI Transfer Monitor (STM) descriptor reserved in SMM save state.
+ */
+#if CONFIG(STM)
+#define STM_PSD_SIZE ALIGN_UP(sizeof(TXT_PROCESSOR_SMM_DESCRIPTOR), 0x100)
+#else
+#define STM_PSD_SIZE 0
+#endif
+
 /* Send cmd to APM_CNT with HAVE_SMI_HANDLER checking. */
 int apm_control(u8 cmd);
 u8 apm_get_apmc(void);

```