1 // SPDX-License-Identifier: GPL-2.0
2 #if defined(__i386__) || defined(__x86_64__)
3
4 #include <fcntl.h>
5 #include <stdio.h>
6 #include <unistd.h>
7 #include <stdint.h>
8
9 #include "helpers/helpers.h"
10
11 /* Intel specific MSRs */
12 #define MSR_IA32_PERF_STATUS 0x198
13 #define MSR_IA32_MISC_ENABLES 0x1a0
14 #define MSR_NEHALEM_TURBO_RATIO_LIMIT 0x1ad
15
16 /*
17 * read_msr
18 *
19 * Will return 0 on success and -1 on failure.
20 * Possible errno values could be:
21 * EFAULT -If the read/write did not fully complete
22 * EIO -If the CPU does not support MSRs
23 * ENXIO -If the CPU does not exist
24 */
25
26 int read_msr(int cpu, unsigned int idx, unsigned long long *val)
27 {
28 int fd;
29 char msr_file_name[64];
30
31 sprintf(msr_file_name, "/dev/cpu/%d/msr", cpu);
32 fd = open(msr_file_name, O_RDONLY);
33 if (fd < 0)
34 return -1;
35 if (lseek(fd, idx, SEEK_CUR) == -1)
36 goto err;
37 if (read(fd, val, sizeof *val) != sizeof *val)
38 goto err;
39 close(fd);
40 return 0;
41 err:
42 close(fd);
43 return -1;
44 }
45
46 /*
47 * write_msr
48 *
49 * Will return 0 on success and -1 on failure.
50 * Possible errno values could be:
51 * EFAULT -If the read/write did not fully complete
52 * EIO -If the CPU does not support MSRs
53 * ENXIO -If the CPU does not exist
54 */
55 int write_msr(int cpu, unsigned int idx, unsigned long long val)
56 {
57 int fd;
58 char msr_file_name[64];
59
60 sprintf(msr_file_name, "/dev/cpu/%d/msr", cpu);
61 fd = open(msr_file_name, O_WRONLY);
62 if (fd < 0)
63 return -1;
64 if (lseek(fd, idx, SEEK_CUR) == -1)
65 goto err;
66 if (write(fd, &val, sizeof val) != sizeof val)
67 goto err;
68 close(fd);
69 return 0;
70 err:
71 close(fd);
72 return -1;
73 }
74
75 unsigned long long msr_intel_get_turbo_ratio(unsigned int cpu)
76 {
77 unsigned long long val;
78 int ret;
79
80 if (!(cpupower_cpu_info.caps & CPUPOWER_CAP_HAS_TURBO_RATIO))
81 return -1;
82
83 ret = read_msr(cpu, MSR_NEHALEM_TURBO_RATIO_LIMIT, &val);
84 if (ret)
85 return ret;
86 return val;
87 }
88 #endif
89
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