89 lines · c
1// SPDX-License-Identifier: GPL-2.02#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 0x19813#define MSR_IA32_MISC_ENABLES 0x1a014#define MSR_NEHALEM_TURBO_RATIO_LIMIT 0x1ad15 16/*17 * read_msr18 *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 complete22 * EIO -If the CPU does not support MSRs23 * ENXIO -If the CPU does not exist24 */25 26int 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_msr48 *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 complete52 * EIO -If the CPU does not support MSRs53 * ENXIO -If the CPU does not exist54 */55int 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 75unsigned 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#endif89