x86/cpu/bugs: Make retpoline module warning conditional

(cherry picked from commit e383095c)

If sysfs is disabled and RETPOLINE not defined:

arch/x86/kernel/cpu/bugs.c:97:13: warning: ‘spectre_v2_bad_module’ defined but not used
[-Wunused-variable]
 static bool spectre_v2_bad_module;

Hide it.

Fixes: caf7501a ("module/retpoline: Warn about missing retpoline in module")
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/kernel/cpu/bugs.c

@@ -93,9 +93,10 @@ static const char *spectre_v2_strings[] = {
 #define pr_fmt(fmt)     "Spectre V2 : " fmt
 
 static enum spectre_v2_mitigation spectre_v2_enabled = SPECTRE_V2_NONE;
-static bool spectre_v2_bad_module;
 
 #ifdef RETPOLINE
+static bool spectre_v2_bad_module;
+
 bool retpoline_module_ok(bool has_retpoline)
 {
 	if (spectre_v2_enabled == SPECTRE_V2_NONE || has_retpoline)
@@ -105,6 +106,13 @@ bool retpoline_module_ok(bool has_retpoline)
 	spectre_v2_bad_module = true;
 	return false;
 }
+
+static inline const char *spectre_v2_module_string(void)
+{
+	return spectre_v2_bad_module ? " - vulnerable module loaded" : "";
+}
+#else
+static inline const char *spectre_v2_module_string(void) { return ""; }
 #endif
 
 static void __init spec2_print_if_insecure(const char *reason)
@@ -299,7 +307,7 @@ ssize_t cpu_show_spectre_v2(struct device *dev,
 		return sprintf(buf, "Not affected\n");
 
 	return sprintf(buf, "%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
-		       boot_cpu_has(X86_FEATURE_IBPB) ? ", IPBP" : "",
-		       spectre_v2_bad_module ? " - vulnerable module loaded" : "");
+		       boot_cpu_has(X86_FEATURE_IBPB) ? ", IBPB" : "",
+		       spectre_v2_module_string());
 }
 #endif