[Patch v4 06/18] smt: Create cpu_smt_enabled static key for SMT specific code

From: Tim Chen <tim.c.chen@linux.intel.com>
To: Jiri Kosina <jikos@kernel.org>, Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	David Woodhouse <dwmw@amazon.co.uk>,
	Andi Kleen <ak@linux.intel.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Casey Schaufler <casey.schaufler@intel.com>,
	Asit Mallick <asit.k.mallick@intel.com>,
	Arjan van de Ven <arjan@linux.intel.com>,
	Jon Masters <jcm@redhat.com>, Waiman Long <longman9394@gmail.com>,
	linux-kernel@vger.kernel.org, x86@kernel.org
Subject: [Patch v4 06/18] smt: Create cpu_smt_enabled static key for SMT specific code
Date: Tue, 30 Oct 2018 11:49:13 -0700	[thread overview]
Message-ID: <89b4d2ca342d18404535a3cc88956d85e4ec0279.1540923609.git.tim.c.chen@linux.intel.com> (raw)
In-Reply-To: <cover.1540923609.git.tim.c.chen@linux.intel.com>
In-Reply-To: <cover.1540923609.git.tim.c.chen@linux.intel.com>

Create cpu_smt_enabled static key used for enabling
SMT specific code paths.

Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
---
 include/linux/cpu.h |  1 +
 kernel/cpu.c        | 12 ++++++++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 218df7f..b54f085 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -188,5 +188,6 @@ static inline void cpu_smt_disable(bool force) { }
 static inline void cpu_smt_check_topology_early(void) { }
 static inline void cpu_smt_check_topology(void) { }
 #endif
+DECLARE_STATIC_KEY_TRUE(cpu_smt_enabled);
 
 #endif /* _LINUX_CPU_H_ */
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 3adecda..03170c8 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -349,6 +349,8 @@ EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
 #ifdef CONFIG_HOTPLUG_SMT
 enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
 EXPORT_SYMBOL_GPL(cpu_smt_control);
+DEFINE_STATIC_KEY_TRUE(cpu_smt_enabled);
+EXPORT_SYMBOL_GPL(cpu_smt_enabled);
 
 static bool cpu_smt_available __read_mostly;
 
@@ -364,6 +366,7 @@ void __init cpu_smt_disable(bool force)
 	} else {
 		cpu_smt_control = CPU_SMT_DISABLED;
 	}
+	static_branch_disable(&cpu_smt_enabled);
 }
 
 /*
@@ -373,8 +376,10 @@ void __init cpu_smt_disable(bool force)
  */
 void __init cpu_smt_check_topology_early(void)
 {
-	if (!topology_smt_supported())
+	if (!topology_smt_supported()) {
 		cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
+		static_branch_disable(&cpu_smt_enabled);
+	}
 }
 
 /*
@@ -386,8 +391,10 @@ void __init cpu_smt_check_topology_early(void)
  */
 void __init cpu_smt_check_topology(void)
 {
-	if (!cpu_smt_available)
+	if (!cpu_smt_available) {
 		cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
+		static_branch_disable(&cpu_smt_enabled);
+	}
 }
 
 static int __init smt_cmdline_disable(char *str)
@@ -2072,6 +2079,7 @@ static int cpuhp_smt_enable(void)
 
 	cpu_maps_update_begin();
 	cpu_smt_control = CPU_SMT_ENABLED;
+	static_branch_enable(&cpu_smt_enabled);
 	arch_smt_update();
 	for_each_present_cpu(cpu) {
 		/* Skip online CPUs and CPUs on offline nodes */
-- 
2.9.4

