soc/intel/alderlake: Remove dependency of FSP-S CpuMpPei Module

This patch fixes a hidden issue present inside FSP-S while coreboot
decides to skip performing MP initialization by overriding FSP-S UPDs
as below:
 1. CpuMpPpi  ------> Passing `NULL` as coreboot assume FSP don't need
                      to use coreboot wrapper for performing any
                      operation over APs.

 2. SkipMpInit -----> Set `1` to let FSP know that coreboot decided
                      to skip FSP running CPU feature programming.

Unfortunately, the assumption of coreboot is not aligned with FSP when
it comes to the behaviour of `CpuMpPpi` UPD. FSP assumes ownership of
the APs (Application Processors) upon passing `NULL` pointer to the
`CpuMpPpi` FSP-S UPD.

FSP-S creates its own infrastructure code after seeing the CpuMpPpi
UPD is set to `NULL`. FSP requires the CpuMpPei module, file name `UefiCpuPkg/CpuMpPei/CpuMpPei.c`, function name `InitializeCpuMpWorker`
to perform those additional initialization which is not relevant for
the coreboot upon selecting the SkipMpInit UPD to 1 (a.k.a avoid
running CPU feature programming on APs).

Additionally, FSP-S binary size has increased by ~30KB (irrespective of
being compressed) with the inclusion of the CpuMpPei module, which is
eventually not meaningful for coreboot.

Hence, this patch selects `MP_SERVICES_PPI_V2_NOOP` config
unconditionally to ensure pass a valid pointer to the `CpuMpPpi` UPD
and avoid APs getting hijacked by FSP while coreboot decides to set
SkipMpInit UPD.

Ideally, FSP should have avoided all AP related operations when
coreboot requested FSP to skip MP init by overriding required UPDs.

TEST=Able to drop CpuMpPei Module from FSP and boot to Chrome OS on
Google/Redrix, Kano, Taeko devices with SkipMpInit=1.

Without this patch:

Here is the CPU AP logs coming from the EDK2 (open-source)
[UefiCpuPkg/CpuMpPei/CpuMpPei.c] when coreboot sets `NULL` to the
CpuMpPpi UPD.

[SPEW ]  Loading PEIM EDADEB9D-DDBA-48BD-9D22-C1C169C8C5C6
[SPEW ]  Loading PEIM at 0x00076F9A000 EntryPoint=0x00076FA24E2
         CpuMpPei.efi PROGRESS CODE: V03020002 I0
[SPEW ]  Register PPI Notify: F894643D-C449-42D1-8EA8-85BDD8C65BDE
[SPEW ]  Notify: PPI Guid: F894643D-C449-42D1-8EA8-85BDD8C65BDE,
         Peim notify entry point: 76FA0239
AP Loop Mode is 2
GetMicrocodePatchInfoFromHob: Microcode patch cache HOB is not found.
CPU[0000]: Microcode revision = 00000000, expected = 00000000
[SPEW ]  Register PPI Notify: 8F9D4825-797D-48FC-8471-845025792EF6
Does not find any stored CPU BIST information from PPI!
  APICID - 0x00000000, BIST - 0x00000000
[SPEW ]  Install PPI: 9E9F374B-8F16-4230-9824-5846EE766A97
[SPEW ]  Install PPI: 5CB9CB3D-31A4-480C-9498-29D269BACFBA
[SPEW ]  Install PPI: EE16160A-E8BE-47A6-820A-C6900DB0250A
PROGRESS CODE: V03020003 I0

With this patch:

No instance of `CpuMpPei` has been found in the AP UART log with FSP
debug enabled.

Signed-off-by: Subrata Banik <subratabanik@google.com>
Change-Id: I8ebe0bcfda513e79e791df7ab54b357aa23d295c
Reviewed-on: https://review.coreboot.org/c/coreboot/+/66706
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

2 files changed, 18 insertions, 10 deletions

diff --git a/src/soc/intel/alderlake/Kconfig b/src/soc/intel/alderlake/Kconfig
index f2b7d6ff40..c79eb08c7b 100644
--- a/src/soc/intel/alderlake/Kconfig
+++ b/src/soc/intel/alderlake/Kconfig
@@ -430,6 +430,13 @@ config USE_FSP_MP_INIT
 
 config USE_COREBOOT_MP_INIT
 	bool "Use coreboot MP init"
+	# FSP assumes ownership of the APs (Application Processors)
+	# upon passing `NULL` pointer to the CpuMpPpi FSP-S UPD.
+	# Hence, select `MP_SERVICES_PPI_V2_NOOP` config to pass a valid
+	# pointer to the CpuMpPpi UPD with FSP_UNSUPPORTED type APIs.
+	# This will protect APs from getting hijacked by FSP while coreboot
+	# decides to set SkipMpInit UPD.
+	select MP_SERVICES_PPI_V2_NOOP
 	select RELOAD_MICROCODE_PATCH
 	help
 	  Upon selection, coreboot performs MP Init.
diff --git a/src/soc/intel/alderlake/fsp_params.c b/src/soc/intel/alderlake/fsp_params.c
index 6826306c12..dd17e33d36 100644
--- a/src/soc/intel/alderlake/fsp_params.c
+++ b/src/soc/intel/alderlake/fsp_params.c
@@ -586,22 +586,23 @@ static void fill_fsps_microcode_params(FSP_S_CONFIG *s_cfg,
 static void fill_fsps_cpu_params(FSP_S_CONFIG *s_cfg,
 		const struct soc_intel_alderlake_config *config)
 {
-	if (CONFIG(USE_FSP_MP_INIT)) {
+	/*
+	 * FIXME: FSP assumes ownership of the APs (Application Processors)
+	 * upon passing `NULL` pointer to the CpuMpPpi FSP-S UPD.
+	 * Hence, pass a valid pointer to the CpuMpPpi UPD unconditionally.
+	 * This would avoid APs from getting hijacked by FSP while coreboot
+	 * decides to set SkipMpInit UPD.
+	 */
+	s_cfg->CpuMpPpi = (uintptr_t) mp_fill_ppi_services_data();
+
+	if (CONFIG(USE_FSP_MP_INIT))
 		/*
 		 * Fill `2nd microcode loading FSP UPD` if FSP is running CPU feature
 		 * programming.
 		 */
 		fill_fsps_microcode_params(s_cfg, config);
-		/*
-		 * Use FSP running MP PPI services to perform CPU feature programming
-		 * if Kconfig is enabled
-		 */
-		s_cfg->CpuMpPpi = (uintptr_t) mp_fill_ppi_services_data();
-	} else {
-		/* Use coreboot native driver to perform MP init by default */
-		s_cfg->CpuMpPpi = (uintptr_t)NULL;
+	else
 		s_cfg->SkipMpInit = !CONFIG(USE_INTEL_FSP_MP_INIT);
-	}
 }
 
 static void fill_fsps_igd_params(FSP_S_CONFIG *s_cfg,