linux-kernel - [Patch v4 07/18] x86/smt: Convert cpu_smt_control check to cpu_smt

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Date:   Tue, 30 Oct 2018 11:49:14 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Jiri Kosina <jikos@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Tim Chen <tim.c.chen@...ux.intel.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Casey Schaufler <casey.schaufler@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Jon Masters <jcm@...hat.com>,
        Waiman Long <longman9394@...il.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [Patch v4 07/18] x86/smt: Convert cpu_smt_control check to cpu_smt_enabled static key

Change the SMT code paths check from using cpu_smt_control to
cpu_smt_enabled static key.  This saves a branching check.

Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
---
 arch/x86/kernel/cpu/bugs.c | 2 +-
 arch/x86/kvm/vmx.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 eb07ab6..32d962e 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -355,7 +355,7 @@ void arch_smt_update(void)
 
 	mutex_lock(&spec_ctrl_mutex);
 	mask = x86_spec_ctrl_base;
-	if (cpu_smt_control == CPU_SMT_ENABLED)
+	if (static_branch_likely(&cpu_smt_enabled))
 		mask |= SPEC_CTRL_STIBP;
 	else
 		mask &= ~SPEC_CTRL_STIBP;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 533a327..8ec0ea3 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -11072,7 +11072,7 @@ static int vmx_vm_init(struct kvm *kvm)
 			 * Warn upon starting the first VM in a potentially
 			 * insecure environment.
 			 */
-			if (cpu_smt_control == CPU_SMT_ENABLED)
+			if (static_branch_likely(&cpu_smt_enabled))
 				pr_warn_once(L1TF_MSG_SMT);
 			if (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_NEVER)
 				pr_warn_once(L1TF_MSG_L1D);
-- 
2.9.4