arch/x86: Drop Kconfig AP_SIPI_VECTOR

This was used to check romcc-built bootblock and romstage
agree about the location of 16-bit entrypoint. There was
no need to customize it as bootblock size requirement did
not grow. Just check for a fixed location at 4 GiB - 4 KiB.

With C_ENVIRONMENT_BOOTBLOCK we can have a proper symbol
for the purpose, since it appears in the same compilation
unit. It will adjust if C_ENV_BOOTBLOCK_SIZE changes.

Change-Id: I93f3c37e78ba587455c804de8c57e7e06832a81f
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/30854
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/cpu/Kconfig

@@ -42,12 +42,6 @@ config SMP
 	  This option is used to enable certain functions to make coreboot
 	  work correctly on symmetric multi processor (SMP) systems.
 
-config AP_SIPI_VECTOR
-	hex
-	default 0xfffff000
-	help
-	  This must equal address of ap_sipi_vector from bootblock build.
-
 config	MMX
 	bool
 	help

src/cpu/intel/car/p4-netburst/cache_as_ram.S

@@ -23,7 +23,10 @@
 
 /* Macro to access Local APIC registers at default base. */
 #define LAPIC(x)		$(LAPIC_DEFAULT_BASE | LAPIC_ ## x)
-#define START_IPI_VECTOR	((CONFIG_AP_SIPI_VECTOR >> 12) & 0xff)
+#if !IS_ENABLED(CONFIG_C_ENVIRONMENT_BOOTBLOCK)
+/* Fixed location, ASSERTED in failover.ld if it changes. */
+.set ap_sipi_vector_in_rom, 0xff
+#endif
 
 #define CACHE_AS_RAM_SIZE CONFIG_DCACHE_RAM_SIZE
 #define CACHE_AS_RAM_BASE CONFIG_DCACHE_RAM_BASE
@@ -180,7 +183,8 @@ hyper_threading_cpu:
 
 	/* Send Start IPI to all excluding ourself. */
 	movl	LAPIC(ICR), %edi
-	movl	$(LAPIC_DEST_ALLBUT | LAPIC_DM_STARTUP | START_IPI_VECTOR), %eax
+	movl	$(LAPIC_DEST_ALLBUT | LAPIC_DM_STARTUP), %eax
+	orl	$ap_sipi_vector_in_rom, %eax
 1:	movl	%eax, (%edi)
 	movl	$0x30, %ecx
 2:	pause

src/cpu/x86/16bit/entry16.inc

@@ -28,6 +28,13 @@
  */
 
 #include <arch/rom_segs.h>
+
+#if IS_ENABLED(CONFIG_SIPI_VECTOR_IN_ROM)
+/* Symbol _start16bit must be aligned to 4kB to start AP CPUs with
+ * Startup IPI message without RAM.
+ */
+.align 4096
+#endif
 .code16
 .globl _start16bit
 .type _start16bit, @function

src/cpu/x86/16bit/entry16.ld

@@ -1,2 +1,3 @@
 	gdtptr16_offset = gdtptr16 & 0xffff;
 	nullidt_offset = nullidt & 0xffff;
+	ap_sipi_vector_in_rom = (_start16bit >> 12) & 0xff;