linux-kernel - [PATCH 19/22] x86/srso: Improve i-cache locality for alias mitigation

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Message-ID: <61b4147837d1e0273d094f3d11384fcdcf9b637f.1692580085.git.jpoimboe@kernel.org>
Date:   Sun, 20 Aug 2023 18:19:16 -0700
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Babu Moger <babu.moger@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>, David.Kaplan@....com,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Nikolay Borisov <nik.borisov@...e.com>,
        gregkh@...uxfoundation.org, Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 19/22] x86/srso: Improve i-cache locality for alias mitigation

Move srso_alias_return_thunk() to the same section as
srso_alias_safe_ret() so they can share a cache line.

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 arch/x86/lib/retpoline.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index af3c1f0e4fb8..415521dbe15e 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -166,14 +166,14 @@ SYM_CODE_START_NOALIGN(srso_alias_safe_ret)
 	ret
 	int3
 SYM_FUNC_END(srso_alias_safe_ret)
-	.popsection
 
-SYM_CODE_START(srso_alias_return_thunk)
+SYM_CODE_START_NOALIGN(srso_alias_return_thunk)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
 	call srso_alias_safe_ret
 	ud2
 SYM_CODE_END(srso_alias_return_thunk)
+	.popsection
 
 /*
  * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
-- 
2.41.0