cpufrequtils aperf: Make data collection cpu hotplug proof

Measuring boosting performance fails when some cores are offlined due to
the cores counting not being aware of that fact. Make it more robust and
print an "offline" label for the offlined cores instead of bailing out.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>

utils/aperf.c

diff --git a/utils/aperf.c b/utils/aperf.c
index bbe0d9b..893e8eb 100644
--- a/utils/aperf.c
+++ b/utils/aperf.c
@@ -118,7 +118,7 @@
 	retval = read_msr(cpu, MSR_IA32_APERF, (unsigned long long*)aperf);
 	if (retval < 0)
 		return retval;
-	
+
 	retval = read_msr(cpu, MSR_IA32_MPERF, (unsigned long long*)mperf);
 	if (retval < 0)
 		return retval;
@@ -202,35 +202,20 @@
 	int ret;
 
 	cpu_info->is_valid = 0;
-		
-	ret = cpu_has_effective_freq();
-	if (ret < 0) {
-		fprintf(stderr, "Could not read cpuid, is the cpuid "
-			"driver loaded or compiled into the kernel?\n");
-		return ret;
-	} else if (ret == 0) {
-		fprintf(stderr, "CPU(s) do not support mperf/aperf MSR "
-			"registers\n");
-		return EXIT_FAILURE;
-	}
-	
-	if (cpufreq_get_hardware_limits(cpu, &min, &max)) {
-		fprintf(stderr, "Could not get max frequency (P0), a "
-			"cpufreq driver must be loaded?\n");
-		return EXIT_FAILURE;
-	} else
-		cpu_info->max_freq = max;
+
+	if (cpufreq_get_hardware_limits(cpu, &min, &max))
+		return -EINVAL;
+
+	cpu_info->max_freq = max;
 	
 	ret = get_aperf_mperf(cpu, &aperf, &mperf);
-	if (ret < 0) {
-		fprintf(stderr, "Could not read MSRs, is the msr driver loaded"
-			" or compiled into the kernel?\n");
-		return EXIT_FAILURE;
-	} else {
-		cpu_info->saved_aperf = aperf;
-		cpu_info->saved_mperf = mperf;
-	}
+	if (ret < 0)
+		return -EINVAL;
+
+	cpu_info->saved_aperf = aperf;
+	cpu_info->saved_mperf = mperf;
 	cpu_info->is_valid = 1;
+
 	return 0;
 }
 
@@ -245,7 +230,6 @@
 	printf("%.2u", c0_percent);
 }
 
-
 static int do_measuring_on_cpu(int sleep_time, int once, int cpu)
 {
 	int ret;
@@ -270,13 +254,16 @@
 
 		if (!cpu_info.is_valid)
 			continue;
-		
+
 		ret = get_aperf_mperf(cpu, &current_aperf, &current_mperf);
-		if (ret < 0)
-			return EXIT_FAILURE;
+		if (ret < 0) {
+			printf("\t[offline]\n");
+			continue;
+		}
+
 		mperf_diff = current_mperf - cpu_info.saved_mperf;
 		aperf_diff = current_aperf - cpu_info.saved_aperf;
-		
+
 		get_C_state_time(diff_time, mperf_diff,
 				 cpu_info.max_freq,
 				 &C0_time, &CX_time,
@@ -312,12 +299,12 @@
 
 	cpu_list = (struct avg_perf_cpu_info*)
 		malloc(cpus * sizeof (struct avg_perf_cpu_info));
-	
+
 	for (cpu = 0; cpu < cpus; cpu++) {
 		ret = get_measure_start_info(cpu, &cpu_list[cpu]);
-		if (ret)
-			return ret;
-	}	
+		if   (ret)
+		continue;
+	}
 
 	while(1) {
 		gettimeofday(&start_time, NULL);
@@ -332,13 +319,15 @@
 		       sizeof(struct timeval));
 
 		for (cpu = 0; cpu < cpus; cpu++) {
-			if (!cpu_list[cpu].is_valid)
-				continue;
 
 			ret = get_aperf_mperf(cpu, &current_aperf,
 					      &current_mperf);
-			if (ret < 0)
-				return EXIT_FAILURE;
+
+			if ((ret < 0) || !cpu_list[cpu].is_valid) {
+				printf("\t[offline]\n");
+				continue;
+			}
+
 			mperf_diff = current_mperf - cpu_list[cpu].saved_mperf;
 			aperf_diff = current_aperf - cpu_list[cpu].saved_aperf;
 
@@ -389,6 +378,8 @@
 {
 	int c, ret, cpu = -1;
 	int sleep_time = 1, once = 0;
+	const char *msr_path = "/dev/cpu/0/msr";
+
 	while ( (c = getopt_long(argc,argv,"c:ohi:",long_options,
 				 NULL)) != -1 ) {
 		switch ( c ) {
@@ -406,6 +397,18 @@
 			break;
 		}
 	}
+
+	if (!cpu_has_effective_freq()) {
+		fprintf(stderr, "CPU doesn't support APERF/MPERF!\n");
+		return EXIT_FAILURE;
+	}
+
+	ret = access(msr_path, F_OK);
+	if (ret < 0) {
+		fprintf(stderr, "Error reading %s, load/enable msr.ko\n", msr_path);
+		goto out;
+	}
+
 	printf("CPU\tAverage freq(KHz)\tTime in C0\tTime in"
 	       " Cx\tC0 percentage\n");
 
@@ -413,6 +416,8 @@
 		ret = do_measure_all_cpus(sleep_time, once);
 	else
 		ret = do_measuring_on_cpu(sleep_time, once, cpu);
-	return ret;		
+
+out:
+	return ret;
 }
 /******* Options parsing, main ********/