From: Ben Hutchings <ben@decadent.org.uk>
Date: Thu, 03 Nov 2016 15:25:26 -0600
Subject: cpupower: Fix checks for CPU existence
Forwarded: https://lore.kernel.org/all/20170418023118.GD4152@decadent.org.uk/

Calls to cpufreq_cpu_exists(cpu) were converted to
cpupower_is_cpu_online(cpu) when libcpupower was introduced and the
former function was deleted.  However, cpupower_is_cpu_online() does
not distinguish physically absent and offline CPUs, and does not set
errno.

cpufreq-set has already been fixed (commit c25badc9ceb6).

In cpufreq-bench, which prints an error message for offline CPUs,
properly distinguish and report the zero and negative cases.

Fixes: ac5a181d065d ("cpupower: Add cpuidle parts into library")
Fixes: 53d1cd6b125f ("cpupowerutils: bench - Fix cpu online check")
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
[carnil: Update/Refresh patch for 4.14.17: The issue with the
incorrect check has been fixed with upstream commit 53d1cd6b125f.
Keep in the patch the distinction and report for the zero and
negative cases.]
---
--- a/tools/power/cpupower/bench/system.c
+++ b/tools/power/cpupower/bench/system.c
@@ -45,12 +45,19 @@ long long int get_time()
 
 int set_cpufreq_governor(char *governor, unsigned int cpu)
 {
+	int rc;
 
 	dprintf("set %s as cpufreq governor\n", governor);
 
-	if (cpupower_is_cpu_online(cpu) != 1) {
-		perror("cpufreq_cpu_exists");
-		fprintf(stderr, "error: cpu %u does not exist\n", cpu);
+	rc = cpupower_is_cpu_online(cpu);
+	if (rc != 1) {
+		if (rc < 0)
+			fprintf(stderr, "cpupower_is_cpu_online: %s\n",
+				strerror(-rc));
+		else
+			fprintf(stderr,
+				"error: cpu %u is offline or does not exist\n",
+				cpu);
 		return -1;
 	}