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authorLinus Torvalds <torvalds@linux-foundation.org>2018-12-01 21:35:48 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2018-12-01 21:35:48 +0100
commit4b78317679c4f3782a3cff0ddb269c1fcfde7621 (patch)
treefd3d202ef58da346528625067bc139bc19b28726 /kernel/sched
parentMerge tag 'for-linus-20181201' of git://git.kernel.dk/linux-block (diff)
parentx86/speculation: Provide IBPB always command line options (diff)
downloadlinux-4b78317679c4f3782a3cff0ddb269c1fcfde7621.tar.xz
linux-4b78317679c4f3782a3cff0ddb269c1fcfde7621.zip
Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull STIBP fallout fixes from Thomas Gleixner: "The performance destruction department finally got it's act together and came up with a cure for the STIPB regression: - Provide a command line option to control the spectre v2 user space mitigations. Default is either seccomp or prctl (if seccomp is disabled in Kconfig). prctl allows mitigation opt-in, seccomp enables the migitation for sandboxed processes. - Rework the code to handle the conditional STIBP/IBPB control and remove the now unused ptrace_may_access_sched() optimization attempt - Disable STIBP automatically when SMT is disabled - Optimize the switch_to() logic to avoid MSR writes and invocations of __switch_to_xtra(). - Make the asynchronous speculation TIF updates synchronous to prevent stale mitigation state. As a general cleanup this also makes retpoline directly depend on compiler support and removes the 'minimal retpoline' option which just pretended to provide some form of security while providing none" * 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (31 commits) x86/speculation: Provide IBPB always command line options x86/speculation: Add seccomp Spectre v2 user space protection mode x86/speculation: Enable prctl mode for spectre_v2_user x86/speculation: Add prctl() control for indirect branch speculation x86/speculation: Prepare arch_smt_update() for PRCTL mode x86/speculation: Prevent stale SPEC_CTRL msr content x86/speculation: Split out TIF update ptrace: Remove unused ptrace_may_access_sched() and MODE_IBRS x86/speculation: Prepare for conditional IBPB in switch_mm() x86/speculation: Avoid __switch_to_xtra() calls x86/process: Consolidate and simplify switch_to_xtra() code x86/speculation: Prepare for per task indirect branch speculation control x86/speculation: Add command line control for indirect branch speculation x86/speculation: Unify conditional spectre v2 print functions x86/speculataion: Mark command line parser data __initdata x86/speculation: Mark string arrays const correctly x86/speculation: Reorder the spec_v2 code x86/l1tf: Show actual SMT state x86/speculation: Rework SMT state change sched/smt: Expose sched_smt_present static key ...
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/core.c19
-rw-r--r--kernel/sched/sched.h4
2 files changed, 12 insertions, 11 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 091e089063be..6fedf3a98581 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5738,15 +5738,10 @@ int sched_cpu_activate(unsigned int cpu)
#ifdef CONFIG_SCHED_SMT
/*
- * The sched_smt_present static key needs to be evaluated on every
- * hotplug event because at boot time SMT might be disabled when
- * the number of booted CPUs is limited.
- *
- * If then later a sibling gets hotplugged, then the key would stay
- * off and SMT scheduling would never be functional.
+ * When going up, increment the number of cores with SMT present.
*/
- if (cpumask_weight(cpu_smt_mask(cpu)) > 1)
- static_branch_enable_cpuslocked(&sched_smt_present);
+ if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
+ static_branch_inc_cpuslocked(&sched_smt_present);
#endif
set_cpu_active(cpu, true);
@@ -5790,6 +5785,14 @@ int sched_cpu_deactivate(unsigned int cpu)
*/
synchronize_rcu_mult(call_rcu, call_rcu_sched);
+#ifdef CONFIG_SCHED_SMT
+ /*
+ * When going down, decrement the number of cores with SMT present.
+ */
+ if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
+ static_branch_dec_cpuslocked(&sched_smt_present);
+#endif
+
if (!sched_smp_initialized)
return 0;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 618577fc9aa8..4e524ab589c9 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -23,6 +23,7 @@
#include <linux/sched/prio.h>
#include <linux/sched/rt.h>
#include <linux/sched/signal.h>
+#include <linux/sched/smt.h>
#include <linux/sched/stat.h>
#include <linux/sched/sysctl.h>
#include <linux/sched/task.h>
@@ -936,9 +937,6 @@ 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)