[patch V4 part 1 09/36] x86/entry/64: Avoid pointless code when CONTEXT_TRACKING=n

[Thomas Gleixner]

From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

GAS cannot optimize out the test and conditional jump when context tracking
is disabled and CALL_enter_from_user_mode is an empty macro.

Wrap it in #ifdeffery. Will go away once all this is moved to C.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx>
Acked-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Acked-by: Andy Lutomirski <luto@xxxxxxxxxx>

---
 arch/x86/entry/entry_64.S |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -888,12 +888,14 @@ apicinterrupt IRQ_WORK_VECTOR			irq_work
 	TRACE_IRQS_OFF
 	.endif
 
+#ifdef CONFIG_CONTEXT_TRACKING
 	.if \paranoid == 0
 	testb	$3, CS(%rsp)
 	jz	.Lfrom_kernel_no_context_tracking_\@
 	CALL_enter_from_user_mode
 .Lfrom_kernel_no_context_tracking_\@:
 	.endif
+#endif
 
 	movq	%rsp, %rdi			/* pt_regs pointer */