linux-kernel - [PATCH 2/2] x86/speculation: switch_to_cond

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Date:   Wed,  5 Dec 2018 14:49:28 -0500
From:   Waiman Long <longman@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH 2/2] x86/speculation: switch_to_cond_stibp on is the likely case

Since conditional STIBP is the default, it should be treated as
the likely case. Changes the use of static_branch_unlikely() to
static_branch_likely() for switch_to_cond_stibp.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 arch/x86/kernel/cpu/bugs.c | 2 +-
 arch/x86/kernel/process.c  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index a68b32c..bd11119 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -153,7 +153,7 @@ void __init check_bugs(void)
 			hostval |= ssbd_tif_to_spec_ctrl(ti->flags);
 
 		/* Conditional STIBP enabled? */
-		if (static_branch_unlikely(&switch_to_cond_stibp))
+		if (static_branch_likely(&switch_to_cond_stibp))
 			hostval |= stibp_tif_to_spec_ctrl(ti->flags);
 
 		if (hostval != guestval) {
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 7d31192..39a21ae 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -434,7 +434,7 @@ static __always_inline void __speculation_ctrl_update(unsigned long tifp,
 	 * otherwise avoid the MSR write.
 	 */
 	if (IS_ENABLED(CONFIG_SMP) &&
-	    static_branch_unlikely(&switch_to_cond_stibp)) {
+	    static_branch_likely(&switch_to_cond_stibp)) {
 		updmsr |= !!(tif_diff & _TIF_SPEC_IB);
 		msr |= stibp_tif_to_spec_ctrl(tifn);
 	}
-- 
1.8.3.1