diff --git a/arch/x86/core/CMakeLists.txt b/arch/x86/core/CMakeLists.txt
index 95ae9eb30a7..97e360c4b24 100644
--- a/arch/x86/core/CMakeLists.txt
+++ b/arch/x86/core/CMakeLists.txt
@@ -9,6 +9,7 @@ endif ()
 
 zephyr_library_sources(cpuhalt.c)
 zephyr_library_sources(memmap.c)
+zephyr_library_sources(prep_c.c)
 
 zephyr_library_sources_if_kconfig(pcie.c)
 zephyr_library_sources_if_kconfig(reboot_rst_cnt.c)
diff --git a/arch/x86/core/ia32.cmake b/arch/x86/core/ia32.cmake
index c95e37ba4c3..4954a1d0df0 100644
--- a/arch/x86/core/ia32.cmake
+++ b/arch/x86/core/ia32.cmake
@@ -18,7 +18,6 @@ zephyr_library_sources(
   ia32/swap.S
   ia32/thread.c
   ia32/spec_ctrl.c
-  ia32/prep_c.c
   )
 
 zephyr_library_sources_ifdef(CONFIG_IRQ_OFFLOAD		ia32/irq_offload.c)
diff --git a/arch/x86/core/intel64/locore.S b/arch/x86/core/intel64/locore.S
index 42e1136a722..7440d7cc2df 100644
--- a/arch/x86/core/intel64/locore.S
+++ b/arch/x86/core/intel64/locore.S
@@ -108,20 +108,6 @@ __start:
 	rep stosq
 #endif
 
-#ifdef CONFIG_MULTIBOOT_INFO
-	/* If EBX isn't 0, then we have a valid multiboot info struct. */
-
-	testl %ebx, %ebx
-	jz 1f
-	movl %ebx, %esi
-
-	movl $__MULTIBOOT_INFO_SIZEOF, %ecx
-	movq $multiboot_info, %rdi
-	rep
-	movsb
-1:
-#endif /* CONFIG_MULTIBOOT_INFO */
-
 	/*
 	 * set up SSE in case something uses the floating-point unit during
 	 * early initialization (either directly, or if GCC gets clever)
@@ -132,7 +118,8 @@ __start:
 
 	/* don't replace CALL with JMP; honor the ABI stack alignment! */
 
-	call z_cstart
+	movl %ebx, %edi		/* multiboot pointer (or NULL) */
+	call z_x86_prep_c	/* enter kernel; never returns */
 
 stop:	jmp stop
 
diff --git a/arch/x86/core/offsets/offsets.c b/arch/x86/core/offsets/offsets.c
index 42f683687a7..0cd81ac7f0c 100644
--- a/arch/x86/core/offsets/offsets.c
+++ b/arch/x86/core/offsets/offsets.c
@@ -16,8 +16,4 @@
 
 GEN_OFFSET_SYM(_thread_arch_t, flags);
 
-/* size of struct multiboot_info, used by crt0.S/locore.S */
-
-GEN_ABSOLUTE_SYM(__MULTIBOOT_INFO_SIZEOF, sizeof(struct multiboot_info));
-
 GEN_ABS_SYM_END
diff --git a/arch/x86/core/ia32/prep_c.c b/arch/x86/core/prep_c.c
similarity index 79%
rename from arch/x86/core/ia32/prep_c.c
rename to arch/x86/core/prep_c.c
index 3e5093fc0fe..6c3b22e5f46 100644
--- a/arch/x86/core/ia32/prep_c.c
+++ b/arch/x86/core/prep_c.c
@@ -8,11 +8,13 @@
 #include <arch/x86/acpi.h>
 #include <arch/x86/multiboot.h>
 
+extern FUNC_NORETURN void z_cstart(void);
+
 FUNC_NORETURN void z_x86_prep_c(struct multiboot_info *info)
 {
-	_kernel.nested = 0;
-	_kernel.irq_stack = Z_THREAD_STACK_BUFFER(_interrupt_stack) +
-				CONFIG_ISR_STACK_SIZE;
+	_kernel.cpus[0].nested = 0;
+	_kernel.cpus[0].irq_stack = Z_THREAD_STACK_BUFFER(_interrupt_stack) +
+					CONFIG_ISR_STACK_SIZE;
 
 #ifdef CONFIG_X86_VERY_EARLY_CONSOLE
 	z_x86_early_serial_init();