x86: provide 64-bit with a load_sp0 function.

Paravirt guests need to inform the underlying hypervisor whenever the sp0
tss field changes. i386 already has such a function, and we use it for
x86_64 too. There's an unnecessary (for 64-bit) msr handling part in the original
version, and it is placed around an ifdef. Making no more sense in
processor_32.h, it is moved to the common header

Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/process_64.c

@@ -639,7 +639,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 	/*
 	 * Reload esp0, LDT and the page table pointer:
 	 */
-	tss->x86_tss.sp0 = next->sp0;
+	load_sp0(tss, next);
 
 	/* 
 	 * Switch DS and ES.

arch/x86/kernel/smpboot_64.c

@@ -614,7 +614,7 @@ do_rest:
 	start_rip = setup_trampoline();
 
 	init_rsp = c_idle.idle->thread.sp;
-	per_cpu(init_tss, cpu).x86_tss.sp0 = init_rsp;
+	load_sp0(&per_cpu(init_tss, cpu), &c_idle.idle->thread);
 	initial_code = start_secondary;
 	clear_tsk_thread_flag(c_idle.idle, TIF_FORK);
 

include/asm-x86/processor.h

@@ -193,8 +193,22 @@ static inline void native_set_iopl_mask(unsigned mask)
 #endif
 }
 
+static inline void native_load_sp0(struct tss_struct *tss,
+				   struct thread_struct *thread)
+{
+	tss->x86_tss.sp0 = thread->sp0;
+#ifdef CONFIG_X86_32
+	/* Only happens when SEP is enabled, no need to test "SEP"arately */
+	if (unlikely(tss->x86_tss.ss1 != thread->sysenter_cs)) {
+		tss->x86_tss.ss1 = thread->sysenter_cs;
+		wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0);
+	}
+#endif
+}
 
-#ifndef CONFIG_PARAVIRT
+#ifdef CONFIG_PARAVIRT
+#include <asm/paravirt.h>
+#else
 #define __cpuid native_cpuid
 #define paravirt_enabled() 0
 
@@ -206,6 +220,12 @@ static inline void native_set_iopl_mask(unsigned mask)
 #define set_debugreg(value, register)				\
 	native_set_debugreg(register, value)
 
+static inline void load_sp0(struct tss_struct *tss,
+			    struct thread_struct *thread)
+{
+	native_load_sp0(tss, thread);
+}
+
 #define set_iopl_mask native_set_iopl_mask
 #endif /* CONFIG_PARAVIRT */
 

include/asm-x86/processor_32.h

@@ -278,26 +278,6 @@ extern unsigned long thread_saved_pc(struct task_struct *tsk);
 
 #define KSTK_ESP(task) (task_pt_regs(task)->sp)
 
-static inline void native_load_sp0(struct tss_struct *tss, struct thread_struct *thread)
-{
-	tss->x86_tss.sp0 = thread->sp0;
-	/* This can only happen when SEP is enabled, no need to test "SEP"arately */
-	if (unlikely(tss->x86_tss.ss1 != thread->sysenter_cs)) {
-		tss->x86_tss.ss1 = thread->sysenter_cs;
-		wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0);
-	}
-}
-
-#ifdef CONFIG_PARAVIRT
-#include <asm/paravirt.h>
-#else
-
-static inline void load_sp0(struct tss_struct *tss, struct thread_struct *thread)
-{
-	native_load_sp0(tss, thread);
-}
-#endif /* CONFIG_PARAVIRT */
-
 /* generic versions from gas */
 #define GENERIC_NOP1	".byte 0x90\n"
 #define GENERIC_NOP2    	".byte 0x89,0xf6\n"