[S] Change in coreboot[master]: cpu/x86: Set up a separate stack for APs

[Arthur Heymans (Code Review)]

Arthur Heymans has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/69123 )

Change subject: cpu/x86: Set up a separate stack for APs
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cpu/x86: Set up a separate stack for APs

APs use a lot less stack, so set up a separate stack for those in .bss.

Now that CPU_INFO_V2 is the only code path that is used, there is no
need to align stacks in c_start.S.

Change-Id: I7a681a2e3003da0400843daa5d6d6180d952abf5
Signed-off-by: Arthur Heymans 
---
M src/arch/x86/c_start.S
M src/cpu/x86/Kconfig
M src/cpu/x86/mp_init.c
3 files changed, 29 insertions(+), 7 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/23/69123/1

diff --git a/src/arch/x86/c_start.S b/src/arch/x86/c_start.S
index 02a9b89..e4f52e4 100644
--- a/src/arch/x86/c_start.S
+++ b/src/arch/x86/c_start.S
@@ -11,11 +11,9 @@
 .global _estack
 .global _stack_size

-/* Stack alignment is not enforced with rmodule loader, reserve one
- * extra CPU such that alignment can be enforced on entry. */
-.align CONFIG_STACK_SIZE
+.align 16
 _stack:
-.space (CONFIG_MAX_CPUS+1)*CONFIG_STACK_SIZE
+.space CONFIG_STACK_SIZE
 _estack:
 .set _stack_size, _estack - _stack

@@ -76,7 +74,7 @@

/* Set new stack with enforced alignment. */
    movl	$_estack, %esp
-	andl	$(~(CONFIG_STACK_SIZE-1)), %esp
+	andl	$(0xfffffff0), %esp

push_cpu_info

diff --git a/src/cpu/x86/Kconfig b/src/cpu/x86/Kconfig
index 1d6b489..7927e52 100644
--- a/src/cpu/x86/Kconfig
+++ b/src/cpu/x86/Kconfig
@@ -209,4 +209,11 @@
      However, modern OSes use PAT to control cacheability instead of
      using MTRRs.

+config AP_STACK_SIZE
+	hex
+	default 0x200
+	help
+	  This is the amount of stack each AP needs. The BSP stack size can be
+	  larger and is set with STACK_SIZE.
+
 endif # ARCH_X86
diff --git a/src/cpu/x86/mp_init.c b/src/cpu/x86/mp_init.c
index e3b294f..6cfa96e 100644
--- a/src/cpu/x86/mp_init.c
+++ b/src/cpu/x86/mp_init.c
@@ -209,6 +209,8 @@
    park_this_cpu(NULL);
 }

+static __aligned(16) uint8_t ap_stack[CONFIG_AP_STACK_SIZE * CONFIG_MAX_CPUS];
+
 static void setup_default_sipi_vector_params(struct sipi_params *sp)
 {
    sp->gdt = (uintptr_t)&gdt;
@@ -216,8 +218,8 @@
    sp->idt_ptr = (uintptr_t)&idtarg;
    sp->per_cpu_segment_descriptors = (uintptr_t)&per_cpu_segment_descriptors;
    sp->per_cpu_segment_selector = per_cpu_segment_selector;
-	sp->stack_size = CONFIG_STACK_SIZE;
-	sp->stack_top = ALIGN_DOWN((uintptr_t)&_estack, CONFIG_STACK_SIZE);
+	sp->stack_size = CONFIG_AP_STACK_SIZE;
+	sp->stack_top = (uintptr_t)ap_stack + ARRAY_SIZE(ap_stack);
 }

static const unsigned int fixed_mtrrs[NUM_FIXED_MTRRS] = {