arch/x86/kernel/cpu/perfctr-watchdog.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * local apic based NMI watchdog for various CPUs.
   4  *
   5  * This file also handles reservation of performance counters for coordination
   6  * with other users (like oprofile).
   7  *
   8  * Note that these events normally don't tick when the CPU idles. This means
   9  * the frequency varies with CPU load.
  10  *
  11  * Original code for K7/P6 written by Keith Owens
  12  *
  13  */
  14
  15 #include <linux/percpu.h>
  16 #include <linux/export.h>
  17 #include <linux/kernel.h>
  18 #include <linux/bitops.h>
  19 #include <linux/smp.h>
  20 #include <asm/nmi.h>
  21 #include <linux/kprobes.h>
  22
  23 #include <asm/apic.h>
  24 #include <asm/perf_event.h>
  25
  26 /*
  27  * this number is calculated from Intel's MSR_P4_CRU_ESCR5 register and it's
  28  * offset from MSR_P4_BSU_ESCR0.
  29  *
  30  * It will be the max for all platforms (for now)
  31  */
  32 #define NMI_MAX_COUNTER_BITS 66
  33
  34 /*
  35  * perfctr_nmi_owner tracks the ownership of the perfctr registers:
  36  * evtsel_nmi_owner tracks the ownership of the event selection
  37  * - different performance counters/ event selection may be reserved for
  38  *   different subsystems this reservation system just tries to coordinate
  39  *   things a little
  40  */
  41 static DECLARE_BITMAP(perfctr_nmi_owner, NMI_MAX_COUNTER_BITS);
  42 static DECLARE_BITMAP(evntsel_nmi_owner, NMI_MAX_COUNTER_BITS);
  43
  44 /* converts an msr to an appropriate reservation bit */
  45 static inline unsigned int nmi_perfctr_msr_to_bit(unsigned int msr)
  46 {
  47         /* returns the bit offset of the performance counter register */
  48         switch (boot_cpu_data.x86_vendor) {
  49         case X86_VENDOR_AMD:
  50                 if (msr >= MSR_F15H_PERF_CTR)
  51                         return (msr - MSR_F15H_PERF_CTR) >> 1;
  52                 return msr - MSR_K7_PERFCTR0;
  53         case X86_VENDOR_INTEL:
  54                 if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON))
  55                         return msr - MSR_ARCH_PERFMON_PERFCTR0;
  56
  57                 switch (boot_cpu_data.x86) {
  58                 case 6:
  59                         return msr - MSR_P6_PERFCTR0;
  60                 case 11:
  61                         return msr - MSR_KNC_PERFCTR0;
  62                 case 15:
  63                         return msr - MSR_P4_BPU_PERFCTR0;
  64                 }
  65         }
  66         return 0;
  67 }
  68
  69 /*
  70  * converts an msr to an appropriate reservation bit
  71  * returns the bit offset of the event selection register
  72  */
  73 static inline unsigned int nmi_evntsel_msr_to_bit(unsigned int msr)
  74 {
  75         /* returns the bit offset of the event selection register */
  76         switch (boot_cpu_data.x86_vendor) {
  77         case X86_VENDOR_AMD:
  78                 if (msr >= MSR_F15H_PERF_CTL)
  79                         return (msr - MSR_F15H_PERF_CTL) >> 1;
  80                 return msr - MSR_K7_EVNTSEL0;
  81         case X86_VENDOR_INTEL:
  82                 if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON))
  83                         return msr - MSR_ARCH_PERFMON_EVENTSEL0;
  84
  85                 switch (boot_cpu_data.x86) {
  86                 case 6:
  87                         return msr - MSR_P6_EVNTSEL0;
  88                 case 11:
  89                         return msr - MSR_KNC_EVNTSEL0;
  90                 case 15:
  91                         return msr - MSR_P4_BSU_ESCR0;
  92                 }
  93         }
  94         return 0;
  95
  96 }
  97
  98 /* checks for a bit availability (hack for oprofile) */
  99 int avail_to_resrv_perfctr_nmi_bit(unsigned int counter)
 100 {
 101         BUG_ON(counter > NMI_MAX_COUNTER_BITS);
 102
 103         return !test_bit(counter, perfctr_nmi_owner);
 104 }
 105 EXPORT_SYMBOL(avail_to_resrv_perfctr_nmi_bit);
 106
 107 int reserve_perfctr_nmi(unsigned int msr)
 108 {
 109         unsigned int counter;
 110
 111         counter = nmi_perfctr_msr_to_bit(msr);
 112         /* register not managed by the allocator? */
 113         if (counter > NMI_MAX_COUNTER_BITS)
 114                 return 1;
 115
 116         if (!test_and_set_bit(counter, perfctr_nmi_owner))
 117                 return 1;
 118         return 0;
 119 }
 120 EXPORT_SYMBOL(reserve_perfctr_nmi);
 121
 122 void release_perfctr_nmi(unsigned int msr)
 123 {
 124         unsigned int counter;
 125
 126         counter = nmi_perfctr_msr_to_bit(msr);
 127         /* register not managed by the allocator? */
 128         if (counter > NMI_MAX_COUNTER_BITS)
 129                 return;
 130
 131         clear_bit(counter, perfctr_nmi_owner);
 132 }
 133 EXPORT_SYMBOL(release_perfctr_nmi);
 134
 135 int reserve_evntsel_nmi(unsigned int msr)
 136 {
 137         unsigned int counter;
 138
 139         counter = nmi_evntsel_msr_to_bit(msr);
 140         /* register not managed by the allocator? */
 141         if (counter > NMI_MAX_COUNTER_BITS)
 142                 return 1;
 143
 144         if (!test_and_set_bit(counter, evntsel_nmi_owner))
 145                 return 1;
 146         return 0;
 147 }
 148 EXPORT_SYMBOL(reserve_evntsel_nmi);
 149
 150 void release_evntsel_nmi(unsigned int msr)
 151 {
 152         unsigned int counter;
 153
 154         counter = nmi_evntsel_msr_to_bit(msr);
 155         /* register not managed by the allocator? */
 156         if (counter > NMI_MAX_COUNTER_BITS)
 157                 return;
 158
 159         clear_bit(counter, evntsel_nmi_owner);
 160 }
 161 EXPORT_SYMBOL(release_evntsel_nmi);