linux-kernel - [tip: x86/bugs] x86/srso: Improve i-cache locality for alias mitigation

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Message-ID: <169295877114.27769.14263128082058843579.tip-bot2@tip-bot2>
Date:   Fri, 25 Aug 2023 10:19:31 -0000
From:   "tip-bot2 for Josh Poimboeuf" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Josh Poimboeuf <jpoimboe@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/bugs] x86/srso: Improve i-cache locality for alias mitigation

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     3033c66da13ca363ad2f10dcd858c994e2f4bd00
Gitweb:        https://git.kernel.org/tip/3033c66da13ca363ad2f10dcd858c994e2f4bd00
Author:        Josh Poimboeuf <jpoimboe@...nel.org>
AuthorDate:    Fri, 25 Aug 2023 00:01:44 -07:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Fri, 25 Aug 2023 11:22:00 +02:00

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>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Link: https://lore.kernel.org/r/4f975cf178ab641d3720362f244694408d85ecca.1692919072.git.jpoimboe@kernel.org
---
 arch/x86/lib/retpoline.S | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index cd86aeb..9ab634f 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -177,15 +177,14 @@ SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	int3
 SYM_FUNC_END(srso_alias_safe_ret)
 
-	.section .text..__x86.return_thunk
-
-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)
 
+	.section .text..__x86.return_thunk
 /*
  * Some generic notes on the untraining sequences:
  *