perf machine: Do not require /lib/modules/* on a guest

For some types of work loads and special guest environments, you might
have a kernel that has no kernel modules. The perf kvm record tool
fails instantiate vmlinux maps when the kernel modules directory cannot
be opened, even though the kallsyms has been properly processed. This
leads to a perf kvm report that has no guest symbols resolved.

This patch changes the failure to locate kernel modules to be non-fatal.

Signed-off-by: Jason Wessel <[e-mail]>
Acked-by: David Ahern <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/machine.c

···
 	free(line);
 	fclose(file);
 
-	return machine__set_modules_path(machine);
+	if (machine__set_modules_path(machine) < 0) {
+		pr_debug("Problems setting modules path maps, continuing anyway...\n");
+	}
+	return 0;
 
 out_delete_line:
 	free(line);