x86/boot: Fix data placement around __high_start()

multiboot_ptr should be in __initdata - it is only used on the BSP path.
Furthermore, the .align 8 then .long means that stack_start is misaligned.

Move both into setup.c, which lets the compiler handle the details correctly,
as well as providing proper debug information for them.

Declare stack_start in setup.h and avoid extern-ing it locally in smpboot.c.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/boot/x86_64.S

@@ -67,14 +67,6 @@ ENTRY(__high_start)
         call    __start_xen
         BUG     /* __start_xen() shouldn't return. */
 
-        .data
-        .align 8
-multiboot_ptr:
-        .long   0
-
-GLOBAL(stack_start)
-        .quad   cpu0_stack + STACK_SIZE - CPUINFO_sizeof
-
         .section .data.page_aligned, "aw", @progbits
         .align PAGE_SIZE, 0
 /*

xen/arch/x86/setup.c

@@ -141,6 +141,12 @@ unsigned long __read_mostly xen_virt_end;
 char __section(".bss.stack_aligned") __aligned(STACK_SIZE)
     cpu0_stack[STACK_SIZE];
 
+/* Used by the BSP/AP paths to find the higher half stack mapping to use. */
+void *stack_start = cpu0_stack + STACK_SIZE - sizeof(struct cpu_info);
+
+/* Used by the boot asm to stash the relocated multiboot info pointer. */
+unsigned int __initdata multiboot_ptr;
+
 struct cpuinfo_x86 __read_mostly boot_cpu_data = { 0, 0, 0, 0, -1 };
 
 unsigned long __read_mostly mmu_cr4_features = XEN_MINIMAL_CR4;

xen/arch/x86/smpboot.c

@@ -42,6 +42,7 @@
 #include <asm/microcode.h>
 #include <asm/msr.h>
 #include <asm/mtrr.h>
+#include <asm/setup.h>
 #include <asm/spec_ctrl.h>
 #include <asm/time.h>
 #include <asm/tboot.h>
@@ -419,8 +420,6 @@ void start_secondary(void *unused)
     startup_cpu_idle_loop();
 }
 
-extern void *stack_start;
-
 static int wakeup_secondary_cpu(int phys_apicid, unsigned long start_eip)
 {
     unsigned long send_status = 0, accept_status = 0;

xen/include/asm-x86/setup.h

@@ -12,6 +12,8 @@ extern char __2M_rwdata_start[], __2M_rwdata_end[];
 extern unsigned long xenheap_initial_phys_start;
 extern uint64_t boot_tsc_stamp;
 
+extern void *stack_start;
+
 void early_cpu_init(void);
 void early_time_init(void);