queue-4.9/0030-sched-Add-sched_smt_active.patch

   1 From b8ef0db49f019de335737e44082f01532d34fe61 Mon Sep 17 00:00:00 2001
   2 From: Ben Hutchings <ben@decadent.org.uk>
   3 Date: Fri, 10 May 2019 00:46:25 +0100
   4 Subject: [PATCH 30/76] sched: Add sched_smt_active()
   5
   6 Add the sched_smt_active() function needed for some x86 speculation
   7 mitigations.  This was introduced upstream by commits 1b568f0aabf2
   8 "sched/core: Optimize SCHED_SMT", ba2591a5993e "sched/smt: Update
   9 sched_smt_present at runtime", c5511d03ec09 "sched/smt: Make
  10 sched_smt_present track topology", and 321a874a7ef8 "sched/smt: Expose
  11 sched_smt_present static key".  The upstream implementation uses the
  12 static_key_{disable,enable}_cpuslocked() functions, which aren't
  13 practical to backport.
  14
  15 Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
  16 Cc: Thomas Gleixner <tglx@linutronix.de>
  17 Cc: Ingo Molnar <mingo@kernel.org>
  18 Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
  19 Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
  20 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  21 ---
  22  include/linux/sched/smt.h | 18 ++++++++++++++++++
  23  kernel/sched/core.c       | 19 +++++++++++++++++++
  24  kernel/sched/sched.h      |  1 +
  25  3 files changed, 38 insertions(+)
  26  create mode 100644 include/linux/sched/smt.h
  27
  28 diff --git a/include/linux/sched/smt.h b/include/linux/sched/smt.h
  29 new file mode 100644
  30 index 000000000000..5209c268c6fd
  31 --- /dev/null
  32 +++ b/include/linux/sched/smt.h
  33 @@ -0,0 +1,18 @@
  34 +/* SPDX-License-Identifier: GPL-2.0 */
  35 +#ifndef _LINUX_SCHED_SMT_H
  36 +#define _LINUX_SCHED_SMT_H
  37 +
  38 +#include <linux/atomic.h>
  39 +
  40 +#ifdef CONFIG_SCHED_SMT
  41 +extern atomic_t sched_smt_present;
  42 +
  43 +static __always_inline bool sched_smt_active(void)
  44 +{
  45 +       return atomic_read(&sched_smt_present);
  46 +}
  47 +#else
  48 +static inline bool sched_smt_active(void) { return false; }
  49 +#endif
  50 +
  51 +#endif
  52 diff --git a/kernel/sched/core.c b/kernel/sched/core.c
  53 index 6b3fff6a6437..50e80b1be2c8 100644
  54 --- a/kernel/sched/core.c
  55 +++ b/kernel/sched/core.c
  56 @@ -7355,11 +7355,22 @@ static int cpuset_cpu_inactive(unsigned int cpu)
  57         return 0;
  58  }
  59
  60 +#ifdef CONFIG_SCHED_SMT
  61 +atomic_t sched_smt_present = ATOMIC_INIT(0);
  62 +#endif
  63 +
  64  int sched_cpu_activate(unsigned int cpu)
  65  {
  66         struct rq *rq = cpu_rq(cpu);
  67         unsigned long flags;
  68
  69 +#ifdef CONFIG_SCHED_SMT
  70 +       /*
  71 +        * When going up, increment the number of cores with SMT present.
  72 +        */
  73 +       if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
  74 +               atomic_inc(&sched_smt_present);
  75 +#endif
  76         set_cpu_active(cpu, true);
  77
  78         if (sched_smp_initialized) {
  79 @@ -7408,6 +7419,14 @@ int sched_cpu_deactivate(unsigned int cpu)
  80         else
  81                 synchronize_rcu();
  82
  83 +#ifdef CONFIG_SCHED_SMT
  84 +       /*
  85 +        * When going down, decrement the number of cores with SMT present.
  86 +        */
  87 +       if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
  88 +               atomic_dec(&sched_smt_present);
  89 +#endif
  90 +
  91         if (!sched_smp_initialized)
  92                 return 0;
  93
  94 diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
  95 index ec6e838e991a..15c08752926b 100644
  96 --- a/kernel/sched/sched.h
  97 +++ b/kernel/sched/sched.h
  98 @@ -2,6 +2,7 @@
  99  #include <linux/sched.h>
 100  #include <linux/sched/sysctl.h>
 101  #include <linux/sched/rt.h>
 102 +#include <linux/sched/smt.h>
 103  #include <linux/u64_stats_sync.h>
 104  #include <linux/sched/deadline.h>
 105  #include <linux/kernel_stat.h>
 106 --
 107 2.21.0
 108