x86: rework __per_cpu_load adjustments

Impact: cleanup

Use cpu_number to determine if the adjustment is necessary.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

arch/x86/kernel/head_64.S

@@ -207,19 +207,15 @@ ENTRY(secondary_startup_64)
 
 #ifdef CONFIG_SMP
 	/*
-	 * early_gdt_base should point to the gdt_page in static percpu init
-	 * data area.  Computing this requires two symbols - __per_cpu_load
-	 * and per_cpu__gdt_page.  As linker can't do no such relocation, do
-	 * it by hand.  As early_gdt_descr is manipulated by C code for
-	 * secondary CPUs, this should be done only once for the boot CPU
-	 * when early_gdt_descr_base contains zero.
+	 * Fix up static pointers that need __per_cpu_load added.  The assembler
+	 * is unable to do this directly.  This is only needed for the boot cpu.
+	 * These values are set up with the correct base addresses by C code for
+	 * secondary cpus.
 	 */
-	movq	early_gdt_descr_base(%rip), %rax
-	testq	%rax, %rax
-	jnz	1f
-	movq	$__per_cpu_load, %rax
-	addq	$per_cpu__gdt_page, %rax
-	movq	%rax, early_gdt_descr_base(%rip)
+	movq	initial_gs(%rip), %rax
+	cmpl	$0, per_cpu__cpu_number(%rax)
+	jne	1f
+	addq	%rax, early_gdt_descr_base(%rip)
 1:
 #endif
 	/*
@@ -431,12 +427,8 @@ NEXT_PAGE(level2_spare_pgt)
 	.globl early_gdt_descr
 early_gdt_descr:
 	.word	GDT_ENTRIES*8-1
-#ifdef CONFIG_SMP
 early_gdt_descr_base:
-	.quad   0x0000000000000000
-#else
 	.quad	per_cpu__gdt_page
-#endif
 
 ENTRY(phys_base)
 	/* This must match the first entry in level2_kernel_pgt */