1 // SPDX-License-Identifier: GPL-2.0
2 #if defined(__i386__) || defined(__x86_64__)
9 #include "helpers/helpers.h"
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
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
26 int read_msr(int cpu
, unsigned int idx
, unsigned long long *val
)
29 char msr_file_name
[64];
31 sprintf(msr_file_name
, "/dev/cpu/%d/msr", cpu
);
32 fd
= open(msr_file_name
, O_RDONLY
);
35 if (lseek(fd
, idx
, SEEK_CUR
) == -1)
37 if (read(fd
, val
, sizeof *val
) != sizeof *val
)
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
55 int write_msr(int cpu
, unsigned int idx
, unsigned long long val
)
58 char msr_file_name
[64];
60 sprintf(msr_file_name
, "/dev/cpu/%d/msr", cpu
);
61 fd
= open(msr_file_name
, O_WRONLY
);
64 if (lseek(fd
, idx
, SEEK_CUR
) == -1)
66 if (write(fd
, &val
, sizeof val
) != sizeof val
)
75 unsigned long long msr_intel_get_turbo_ratio(unsigned int cpu
)
77 unsigned long long val
;
80 if (!(cpupower_cpu_info
.caps
& CPUPOWER_CAP_HAS_TURBO_RATIO
))
83 ret
= read_msr(cpu
, MSR_NEHALEM_TURBO_RATIO_LIMIT
, &val
);