x86,static_call: Fix static-call vs return-thunk

Commit

  7825451 ("static_call: Add call depth tracking support")

failed to realize the problem fixed there is not specific to call depth
tracking but applies to all return-thunk uses.

Move the fix to the appropriate place and condition.

Fixes: ee88d36 ("x86,static_call: Use alternative RET encoding")
Reported-by: David Kaplan <David.Kaplan@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>

Author: Peter Zijlstra

arch/x86/kernel/alternative.c

@@ -720,6 +720,9 @@ void __init_or_module noinline apply_returns(s32 *start, s32 *end)
 {
 	s32 *s;
 
+	if (cpu_feature_enabled(X86_FEATURE_RETHUNK))
+		static_call_force_reinit();
+
 	for (s = start; s < end; s++) {
 		void *dest = NULL, *addr = (void *)s + *s;
 		struct insn insn;

arch/x86/kernel/callthunks.c

@@ -272,7 +272,6 @@ void __init callthunks_patch_builtin_calls(void)
 	pr_info("Setting up call depth tracking\n");
 	mutex_lock(&text_mutex);
 	callthunks_setup(&cs, &builtin_coretext);
-	static_call_force_reinit();
 	thunks_initialized = true;
 	mutex_unlock(&text_mutex);
 }