tools/power/turbostat: Fallback to an MSR read for EPB

Commit

  6d6501d912a9 ("tools/power/turbostat: Read energy_perf_bias from sysfs")

converted turbostat to read the energy_perf_bias value from sysfs.
However, older kernels which do not have that file yet, would fail. For
those, fall back to the MSR reading.

Fixes: 6d6501d912a9 ("tools/power/turbostat: Read energy_perf_bias from sysfs")
Reported-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Tested-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Link: https://lkml.kernel.org/r/20210127132444.981120-1-dedekind1@gmail.com

diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index 389ea52..a7c4f07 100644 (file)
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -1834,12 +1834,15 @@ int get_mp(int cpu, struct msr_counter *mp, unsigned long long *counterp)
 int get_epb(int cpu)
 {
        char path[128 + PATH_BYTES];
+       unsigned long long msr;
        int ret, epb = -1;
        FILE *fp;
 
        sprintf(path, "/sys/devices/system/cpu/cpu%d/power/energy_perf_bias", cpu);
 
-       fp = fopen_or_die(path, "r");
+       fp = fopen(path, "r");
+       if (!fp)
+               goto msr_fallback;
 
        ret = fscanf(fp, "%d", &epb);
        if (ret != 1)
@@ -1848,6 +1851,11 @@ int get_epb(int cpu)
        fclose(fp);
 
        return epb;
+
+msr_fallback:
+       get_msr(cpu, MSR_IA32_ENERGY_PERF_BIAS, &msr);
+
+       return msr & 0xf;
 }
 
 void get_apic_id(struct thread_data *t)