queue-4.4/sched-add-sched_smt_active.patch

   1 From foo@baz Tue 14 May 2019 08:29:35 PM CEST
   2 From: Ben Hutchings <ben@decadent.org.uk>
   3 Date: Fri, 10 May 2019 00:46:25 +0100
   4 Subject: sched: Add sched_smt_active()
   5
   6 From: Ben Hutchings <ben@decadent.org.uk>
   7
   8 Add the sched_smt_active() function needed for some x86 speculation
   9 mitigations.  This was introduced upstream by commits 1b568f0aabf2
  10 "sched/core: Optimize SCHED_SMT", ba2591a5993e "sched/smt: Update
  11 sched_smt_present at runtime", c5511d03ec09 "sched/smt: Make
  12 sched_smt_present track topology", and 321a874a7ef8 "sched/smt: Expose
  13 sched_smt_present static key".  The upstream implementation uses the
  14 static_key_{disable,enable}_cpuslocked() functions, which aren't
  15 practical to backport.
  16
  17 Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
  18 Cc: Thomas Gleixner <tglx@linutronix.de>
  19 Cc: Ingo Molnar <mingo@kernel.org>
  20 Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
  21 Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
  22 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  23 ---
  24  include/linux/sched/smt.h |   18 ++++++++++++++++++
  25  kernel/sched/core.c       |   24 ++++++++++++++++++++++++
  26  kernel/sched/sched.h      |    1 +
  27  3 files changed, 43 insertions(+)
  28  create mode 100644 include/linux/sched/smt.h
  29
  30 --- /dev/null
  31 +++ b/include/linux/sched/smt.h
  32 @@ -0,0 +1,18 @@
  33 +/* SPDX-License-Identifier: GPL-2.0 */
  34 +#ifndef _LINUX_SCHED_SMT_H
  35 +#define _LINUX_SCHED_SMT_H
  36 +
  37 +#include <linux/atomic.h>
  38 +
  39 +#ifdef CONFIG_SCHED_SMT
  40 +extern atomic_t sched_smt_present;
  41 +
  42 +static __always_inline bool sched_smt_active(void)
  43 +{
  44 +       return atomic_read(&sched_smt_present);
  45 +}
  46 +#else
  47 +static inline bool sched_smt_active(void) { return false; }
  48 +#endif
  49 +
  50 +#endif
  51 --- a/kernel/sched/core.c
  52 +++ b/kernel/sched/core.c
  53 @@ -5610,6 +5610,10 @@ static void set_cpu_rq_start_time(void)
  54         rq->age_stamp = sched_clock_cpu(cpu);
  55  }
  56
  57 +#ifdef CONFIG_SCHED_SMT
  58 +atomic_t sched_smt_present = ATOMIC_INIT(0);
  59 +#endif
  60 +
  61  static int sched_cpu_active(struct notifier_block *nfb,
  62                                       unsigned long action, void *hcpu)
  63  {
  64 @@ -5626,11 +5630,23 @@ static int sched_cpu_active(struct notif
  65                  * set_cpu_online(). But it might not yet have marked itself
  66                  * as active, which is essential from here on.
  67                  */
  68 +#ifdef CONFIG_SCHED_SMT
  69 +               /*
  70 +                * When going up, increment the number of cores with SMT present.
  71 +                */
  72 +               if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
  73 +                       atomic_inc(&sched_smt_present);
  74 +#endif
  75                 set_cpu_active(cpu, true);
  76                 stop_machine_unpark(cpu);
  77                 return NOTIFY_OK;
  78
  79         case CPU_DOWN_FAILED:
  80 +#ifdef CONFIG_SCHED_SMT
  81 +               /* Same as for CPU_ONLINE */
  82 +               if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
  83 +                       atomic_inc(&sched_smt_present);
  84 +#endif
  85                 set_cpu_active(cpu, true);
  86                 return NOTIFY_OK;
  87
  88 @@ -5645,7 +5661,15 @@ static int sched_cpu_inactive(struct not
  89         switch (action & ~CPU_TASKS_FROZEN) {
  90         case CPU_DOWN_PREPARE:
  91                 set_cpu_active((long)hcpu, false);
  92 +#ifdef CONFIG_SCHED_SMT
  93 +               /*
  94 +                * When going down, decrement the number of cores with SMT present.
  95 +                */
  96 +               if (cpumask_weight(cpu_smt_mask((long)hcpu)) == 2)
  97 +                       atomic_dec(&sched_smt_present);
  98 +#endif
  99                 return NOTIFY_OK;
 100 +
 101         default:
 102                 return NOTIFY_DONE;
 103         }
 104 --- a/kernel/sched/sched.h
 105 +++ b/kernel/sched/sched.h
 106 @@ -2,6 +2,7 @@
 107  #include <linux/sched.h>
 108  #include <linux/sched/sysctl.h>
 109  #include <linux/sched/rt.h>
 110 +#include <linux/sched/smt.h>
 111  #include <linux/sched/deadline.h>
 112  #include <linux/mutex.h>
 113  #include <linux/spinlock.h>