linux-kernel - [RFC][PATCH 03/17] x86/cpu: Make srso_untrain

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Message-ID: <20230809072200.646688083@infradead.org>
Date:   Wed, 09 Aug 2023 09:12:21 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        David.Kaplan@....com, Andrew.Cooper3@...rix.com,
        jpoimboe@...nel.org, gregkh@...uxfoundation.org
Subject: [RFC][PATCH 03/17] x86/cpu: Make srso_untrain_ret consistent

This does change srso_untrain_ret a little to be more consistent with
srso_alias_untrain_ret (and zen_untrain_ret). Specifically I made
srso_untrain_ret tail-call the srso_return_thunk, instead of doing the
call directly. This matches how srso_alias_untrain_ret amd
zen_untrain_ret also tail-call their respective return_thunk.

If this is a problem this can be easily fixed and a comment added to
explain -- but this way they all end with a tail-call to their own
return-thunk, which is nice and consistent.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/lib/retpoline.S |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -262,7 +262,7 @@ SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLO
 	int3
 	/* end of movabs */
 	lfence
-	call srso_safe_ret
+	jmp srso_return_thunk
 	int3
 SYM_CODE_END(srso_safe_ret)
 SYM_FUNC_END(srso_untrain_ret)