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.
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 */
41static DECLARE_BITMAP(perfctr_nmi_owner, NMI_MAX_COUNTER_BITS);
42static DECLARE_BITMAP(evntsel_nmi_owner, NMI_MAX_COUNTER_BITS);
43
44/* converts an msr to an appropriate reservation bit */
45static 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 break;
67 case X86_VENDOR_ZHAOXIN:
68 case X86_VENDOR_CENTAUR:
69 return msr - MSR_ARCH_PERFMON_PERFCTR0;
70 }
71 return 0;
72}
73
74/*
75 * converts an msr to an appropriate reservation bit
76 * returns the bit offset of the event selection register
77 */
78static inline unsigned int nmi_evntsel_msr_to_bit(unsigned int msr)
79{
80 /* returns the bit offset of the event selection register */
81 switch (boot_cpu_data.x86_vendor) {
82 case X86_VENDOR_HYGON:
83 case X86_VENDOR_AMD:
84 if (msr >= MSR_F15H_PERF_CTL)
85 return (msr - MSR_F15H_PERF_CTL) >> 1;
86 return msr - MSR_K7_EVNTSEL0;
87 case X86_VENDOR_INTEL:
88 if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON))
89 return msr - MSR_ARCH_PERFMON_EVENTSEL0;
90
91 switch (boot_cpu_data.x86) {
92 case 6:
93 return msr - MSR_P6_EVNTSEL0;
94 case 11:
95 return msr - MSR_KNC_EVNTSEL0;
96 case 15:
97 return msr - MSR_P4_BSU_ESCR0;
98 }
99 break;
100 case X86_VENDOR_ZHAOXIN:
101 case X86_VENDOR_CENTAUR:
102 return msr - MSR_ARCH_PERFMON_EVENTSEL0;
103 }
104 return 0;
105
106}
107
108int reserve_perfctr_nmi(unsigned int msr)
109{
110 unsigned int counter;
111
112 counter = nmi_perfctr_msr_to_bit(msr);
113 /* register not managed by the allocator? */
114 if (counter > NMI_MAX_COUNTER_BITS)
115 return 1;
116
117 if (!test_and_set_bit(nr: counter, addr: perfctr_nmi_owner))
118 return 1;
119 return 0;
120}
121EXPORT_SYMBOL(reserve_perfctr_nmi);
122
123void release_perfctr_nmi(unsigned int msr)
124{
125 unsigned int counter;
126
127 counter = nmi_perfctr_msr_to_bit(msr);
128 /* register not managed by the allocator? */
129 if (counter > NMI_MAX_COUNTER_BITS)
130 return;
131
132 clear_bit(nr: counter, addr: perfctr_nmi_owner);
133}
134EXPORT_SYMBOL(release_perfctr_nmi);
135
136int reserve_evntsel_nmi(unsigned int msr)
137{
138 unsigned int counter;
139
140 counter = nmi_evntsel_msr_to_bit(msr);
141 /* register not managed by the allocator? */
142 if (counter > NMI_MAX_COUNTER_BITS)
143 return 1;
144
145 if (!test_and_set_bit(nr: counter, addr: evntsel_nmi_owner))
146 return 1;
147 return 0;
148}
149EXPORT_SYMBOL(reserve_evntsel_nmi);
150
151void release_evntsel_nmi(unsigned int msr)
152{
153 unsigned int counter;
154
155 counter = nmi_evntsel_msr_to_bit(msr);
156 /* register not managed by the allocator? */
157 if (counter > NMI_MAX_COUNTER_BITS)
158 return;
159
160 clear_bit(nr: counter, addr: evntsel_nmi_owner);
161}
162EXPORT_SYMBOL(release_evntsel_nmi);
163