sched/smt: Expose sched_smt_present static key

Make the scheduler's 'sched_smt_present' static key globaly available, so
it can be used in the x86 speculation control code.

Provide a query function and a stub for the CONFIG_SMP=n case.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Casey Schaufler <casey.schaufler@intel.com>
Cc: Asit Mallick <asit.k.mallick@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Jon Masters <jcm@redhat.com>
Cc: Waiman Long <longman9394@gmail.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Dave Stewart <david.c.stewart@intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181125185004.430168326@linutronix.de
CVE-2017-5715

(backported from commit 321a874a7ef85655e93b3206d0f36b4a6097f948)
[tyhicks: Backport to 4.15:
 - Handle context differences in the #include lines of sched.h]
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Juerg Haefliger <juergh@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/include/linux/sched/smt.h b/include/linux/sched/smt.h
new file mode 100644 (file)
index 0000000..c9e0be5
--- /dev/null
+++ b/include/linux/sched/smt.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_SCHED_SMT_H
+#define _LINUX_SCHED_SMT_H
+
+#include <linux/static_key.h>
+
+#ifdef CONFIG_SCHED_SMT
+extern struct static_key_false sched_smt_present;
+
+static __always_inline bool sched_smt_active(void)
+{
+       return static_branch_likely(&sched_smt_present);
+}
+#else
+static inline bool sched_smt_active(void) { return false; }
+#endif
+
+#endif

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index b51f34aa2835be73edb539ef01182736a6cf2af6..41be9d48380f1fad96c212f396c16d21c2942acf 100644 (file)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -20,6 +20,7 @@
 #include <linux/sched/task_stack.h>
 #include <linux/sched/cputime.h>
 #include <linux/sched/init.h>
+#include <linux/sched/smt.h>
 
 #include <linux/u64_stats_sync.h>
 #include <linux/kernel_stat.h>
@@ -827,9 +828,6 @@ static inline int cpu_of(struct rq *rq)
 
 
 #ifdef CONFIG_SCHED_SMT
-
-extern struct static_key_false sched_smt_present;
-
 extern void __update_idle_core(struct rq *rq);
 
 static inline void update_idle_core(struct rq *rq)