x86/spectre: Check CONFIG_RETPOLINE in command line parser

(cherry picked from commit 9471eee9186a46893726e22ebb54cade3f9bc043)

The spectre_v2 option 'auto' does not check whether CONFIG_RETPOLINE is
enabled. As a consequence it fails to emit the appropriate warning and sets
feature flags which have no effect at all.

Add the missing IS_ENABLED() check.

Fixes: da285121560e ("x86/spectre: Add boot time option to select Spectre v2 mitigation")
Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: ak@linux.intel.com
Cc: peterz@infradead.org
Cc: Tomohiro <misono.tomohiro@jp.fujitsu.com>
Cc: dave.hansen@intel.com
Cc: bp@alien8.de
Cc: arjan@linux.intel.com
Cc: dwmw@amazon.co.uk
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/f5892721-7528-3647-08fb-f8d10e65ad87@cn.fujitsu.com
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
[jwang: cherry-pick to 4.4]
Signed-off-by: Jack Wang <jinpu.wang@profitbricks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index e3099c2..d3b8337 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -213,10 +213,10 @@ static void __init spectre_v2_select_mitigation(void)
                return;
 
        case SPECTRE_V2_CMD_FORCE:
-               /* FALLTRHU */
        case SPECTRE_V2_CMD_AUTO:
-               goto retpoline_auto;
-
+               if (IS_ENABLED(CONFIG_RETPOLINE))
+                       goto retpoline_auto;
+               break;
        case SPECTRE_V2_CMD_RETPOLINE_AMD:
                if (IS_ENABLED(CONFIG_RETPOLINE))
                        goto retpoline_amd;