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