x86: load new GDT after setting up boot cpu per-cpu area

Impact: sync 32 and 64-bit code

Merge load_gs_base() into switch_to_new_gdt().  Load the GDT and
per-cpu state for the boot cpu when its new area is set up.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

arch/x86/include/asm/processor.h

@@ -394,11 +394,6 @@ union irq_stack_union {
 
 DECLARE_PER_CPU(union irq_stack_union, irq_stack_union);
 DECLARE_PER_CPU(char *, irq_stack_ptr);
-
-static inline void load_gs_base(int cpu)
-{
-	wrmsrl(MSR_GS_BASE, (unsigned long)per_cpu(irq_stack_union.gs_base, cpu));
-}
 #endif
 
 extern void print_cpu_info(struct cpuinfo_x86 *);

arch/x86/kernel/cpu/common.c

@@ -258,12 +258,17 @@ __u32 cleared_cpu_caps[NCAPINTS] __cpuinitdata;
 void switch_to_new_gdt(void)
 {
 	struct desc_ptr gdt_descr;
+	int cpu = smp_processor_id();
 
-	gdt_descr.address = (long)get_cpu_gdt_table(smp_processor_id());
+	gdt_descr.address = (long)get_cpu_gdt_table(cpu);
 	gdt_descr.size = GDT_SIZE - 1;
 	load_gdt(&gdt_descr);
+	/* Reload the per-cpu base */
 #ifdef CONFIG_X86_32
-	asm("mov %0, %%fs" : : "r" (__KERNEL_PERCPU) : "memory");
+	loadsegment(fs, __KERNEL_PERCPU);
+#else
+	loadsegment(gs, 0);
+	wrmsrl(MSR_GS_BASE, (unsigned long)per_cpu(irq_stack_union.gs_base, cpu));
 #endif
 }
 
@@ -968,10 +973,6 @@ void __cpuinit cpu_init(void)
 	struct task_struct *me;
 	int i;
 
-	loadsegment(fs, 0);
-	loadsegment(gs, 0);
-	load_gs_base(cpu);
-
 #ifdef CONFIG_NUMA
 	if (cpu != 0 && percpu_read(node_number) == 0 &&
 	    cpu_to_node(cpu) != NUMA_NO_NODE)
@@ -993,6 +994,8 @@ void __cpuinit cpu_init(void)
 	 */
 
 	switch_to_new_gdt();
+	loadsegment(fs, 0);
+
 	load_idt((const struct desc_ptr *)&idt_descr);
 
 	memset(me->thread.tls_array, 0, GDT_ENTRY_TLS_ENTRIES * 8);

arch/x86/kernel/setup_percpu.c

@@ -112,14 +112,14 @@ void __init setup_per_cpu_areas(void)
 #ifdef CONFIG_NUMA
 		per_cpu(x86_cpu_to_node_map, cpu) =
 				early_per_cpu_map(x86_cpu_to_node_map, cpu);
+#endif
 #endif
 		/*
 		 * Up to this point, the boot CPU has been using .data.init
-		 * area.  Reload %gs offset for the boot CPU.
+		 * area.  Reload any changed state for the boot CPU.
 		 */
 		if (cpu == boot_cpu_id)
-			load_gs_base(cpu);
-#endif
+			switch_to_new_gdt();
 
 		DBG("PERCPU: cpu %4d %p\n", cpu, ptr);
 	}