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Message-Id: <20200225222648.395059616@linutronix.de>
User-Agent: quilt/0.65
Date:   Tue, 25 Feb 2020 23:16:08 +0100
From:   Thomas Gleixner <tglx@linutronix.de>
To:     LKML <linux-kernel@vger.kernel.org>
Cc:     x86@kernel.org, Steven Rostedt <rostedt@goodmis.org>,
        Brian Gerst <brgerst@gmail.com>,
        Juergen Gross <jgross@suse.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Arnd Bergmann <arnd@arndb.de>
Subject: [patch 02/24] x86/entry/64: Avoid pointless code when CONTEXT_TRACKING=n
References: <20200225221606.511535280@linutronix.de>
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Sender: linux-kernel-owner@vger.kernel.org
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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@linutronix.de>
---
 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
@@ -884,12 +884,14 @@ 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 */