linux-kernel - [PATCH] turbostat: Running on virtual machine is not supported

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Message-Id: <1500987324-507-1-git-send-email-prarit@redhat.com>
Date:   Tue, 25 Jul 2017 08:55:24 -0400
From:   Prarit Bhargava <prarit@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Prarit Bhargava <prarit@...hat.com>,
        Len Brown <len.brown@...el.com>, Len Brown <lenb@...nel.org>
Subject: [PATCH] turbostat: Running on virtual machine is not supported

When running turbostat on a virtual machine the error

turbostat: msr 0 offset 0xe2 read failed: Input/output error

is output to the user.

/dev/msr and perf do not work on a virtual machine.  turbostat is
dependent on that support so turbostat does not work either.

A common way of determining if the system is a virtual machine is to
search /proc/cpuinfo flags entry for "hypervisor".  turbostat must output
a proper error message when found.

Signed-off-by: Prarit Bhargava <prarit@...hat.com>
Cc: Len Brown <len.brown@...el.com>
Cc: Len Brown <lenb@...nel.org>
---
 tools/power/x86/turbostat/turbostat.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index 0dafba2c1e7d..ca1ea68bc4e8 100644
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -5088,6 +5088,34 @@ void cmdline(int argc, char **argv)
 	}
 }
 
+int has_hypervisor(void)
+{
+	FILE *cpuinfo;
+	char *flags, *hypervisor;
+	char *buffer;
+
+	/* On VMs /proc/cpuinfo contains a "flags" entry for hypervisor */
+	cpuinfo = fopen_or_die("/proc/cpuinfo", "ro");
+
+	buffer = malloc(4096);
+	if (!buffer)
+		err(-ENOMEM, "buffer malloc fail");
+
+	fread(buffer, 1024, 1, cpuinfo);
+
+	flags = strstr(buffer, "flags");
+	rewind(cpuinfo);
+	fseek(cpuinfo, flags - buffer, SEEK_SET);
+	fgets(buffer, 4096, cpuinfo);
+	fclose(cpuinfo);
+
+	hypervisor = strstr(buffer, "hypervisor");
+
+	free(buffer);
+
+	return !!hypervisor;
+}
+
 int main(int argc, char **argv)
 {
 	outf = stderr;
@@ -5097,6 +5125,12 @@ int main(int argc, char **argv)
 	if (!quiet)
 		print_version();
 
+	if (has_hypervisor()) {
+		fprintf(outf,
+			"turbostat is not supported on virtual machines.\n");
+		return -ENXIO;
+	}
+
 	probe_sysfs();
 
 	turbostat_init();
-- 
1.8.5.5