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

DEFINITIONS

1. nmi_perfctr_msr_to_bit
2. nmi_evntsel_msr_to_bit
3. avail_to_resrv_perfctr_nmi_bit
4. reserve_perfctr_nmi
5. release_perfctr_nmi
6. reserve_evntsel_nmi
7. release_evntsel_nmi

   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_HYGON:
  50         case X86_VENDOR_AMD:
  51                 if (msr >= MSR_F15H_PERF_CTR)
  52                         return (msr - MSR_F15H_PERF_CTR) >> 1;
  53                 return msr - MSR_K7_PERFCTR0;
  54         case X86_VENDOR_INTEL:
  55                 if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON))
  56                         return msr - MSR_ARCH_PERFMON_PERFCTR0;
  57 
  58                 switch (boot_cpu_data.x86) {
  59                 case 6:
  60                         return msr - MSR_P6_PERFCTR0;
  61                 case 11:
  62                         return msr - MSR_KNC_PERFCTR0;
  63                 case 15:
  64                         return msr - MSR_P4_BPU_PERFCTR0;
  65                 }
  66         }
  67         return 0;
  68 }
  69 
  70 /*
  71  * converts an msr to an appropriate reservation bit
  72  * returns the bit offset of the event selection register
  73  */
  74 static inline unsigned int nmi_evntsel_msr_to_bit(unsigned int msr)
  75 {
  76         /* returns the bit offset of the event selection register */
  77         switch (boot_cpu_data.x86_vendor) {
  78         case X86_VENDOR_HYGON:
  79         case X86_VENDOR_AMD:
  80                 if (msr >= MSR_F15H_PERF_CTL)
  81                         return (msr - MSR_F15H_PERF_CTL) >> 1;
  82                 return msr - MSR_K7_EVNTSEL0;
  83         case X86_VENDOR_INTEL:
  84                 if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON))
  85                         return msr - MSR_ARCH_PERFMON_EVENTSEL0;
  86 
  87                 switch (boot_cpu_data.x86) {
  88                 case 6:
  89                         return msr - MSR_P6_EVNTSEL0;
  90                 case 11:
  91                         return msr - MSR_KNC_EVNTSEL0;
  92                 case 15:
  93                         return msr - MSR_P4_BSU_ESCR0;
  94                 }
  95         }
  96         return 0;
  97 
  98 }
  99 
 100 /* checks for a bit availability (hack for oprofile) */
 101 int avail_to_resrv_perfctr_nmi_bit(unsigned int counter)
 102 {
 103         BUG_ON(counter > NMI_MAX_COUNTER_BITS);
 104 
 105         return !test_bit(counter, perfctr_nmi_owner);
 106 }
 107 EXPORT_SYMBOL(avail_to_resrv_perfctr_nmi_bit);
 108 
 109 int reserve_perfctr_nmi(unsigned int msr)
 110 {
 111         unsigned int counter;
 112 
 113         counter = nmi_perfctr_msr_to_bit(msr);
 114         /* register not managed by the allocator? */
 115         if (counter > NMI_MAX_COUNTER_BITS)
 116                 return 1;
 117 
 118         if (!test_and_set_bit(counter, perfctr_nmi_owner))
 119                 return 1;
 120         return 0;
 121 }
 122 EXPORT_SYMBOL(reserve_perfctr_nmi);
 123 
 124 void release_perfctr_nmi(unsigned int msr)
 125 {
 126         unsigned int counter;
 127 
 128         counter = nmi_perfctr_msr_to_bit(msr);
 129         /* register not managed by the allocator? */
 130         if (counter > NMI_MAX_COUNTER_BITS)
 131                 return;
 132 
 133         clear_bit(counter, perfctr_nmi_owner);
 134 }
 135 EXPORT_SYMBOL(release_perfctr_nmi);
 136 
 137 int reserve_evntsel_nmi(unsigned int msr)
 138 {
 139         unsigned int counter;
 140 
 141         counter = nmi_evntsel_msr_to_bit(msr);
 142         /* register not managed by the allocator? */
 143         if (counter > NMI_MAX_COUNTER_BITS)
 144                 return 1;
 145 
 146         if (!test_and_set_bit(counter, evntsel_nmi_owner))
 147                 return 1;
 148         return 0;
 149 }
 150 EXPORT_SYMBOL(reserve_evntsel_nmi);
 151 
 152 void release_evntsel_nmi(unsigned int msr)
 153 {
 154         unsigned int counter;
 155 
 156         counter = nmi_evntsel_msr_to_bit(msr);
 157         /* register not managed by the allocator? */
 158         if (counter > NMI_MAX_COUNTER_BITS)
 159                 return;
 160 
 161         clear_bit(counter, evntsel_nmi_owner);
 162 }
 163 EXPORT_SYMBOL(release_evntsel_nmi);