linux-kernel - [PATCH v3 3/7] x86/bugs: Exit early if return thunk is already set

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Message-ID: <20250522-eibrs-fix-v3-3-12704e291e1e@linux.intel.com>
Date: Thu, 22 May 2025 18:21:02 -0700
From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To: x86@...nel.org
Cc: David Kaplan <david.kaplan@....com>, linux-kernel@...r.kernel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Josh Poimboeuf <jpoimboe@...nel.org>
Subject: [PATCH v3 3/7] x86/bugs: Exit early if return thunk is already set

When the exact same return thunk is already set, avoid the warning and exit
early. This is to prepare for ITS to also set CDT return thunk independent
of retbleed.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
---
 arch/x86/kernel/cpu/bugs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 94d0de3e61aec32b3b67c8d21f89a8c67b93dff3..354593065025fd7c5727e955d76523777b3da9ee 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -113,6 +113,9 @@ void (*x86_return_thunk)(void) __ro_after_init = __x86_return_thunk;
 
 static void __init set_return_thunk(void *thunk)
 {
+	if (thunk == x86_return_thunk)
+		return;
+
 	if (x86_return_thunk != __x86_return_thunk)
 		pr_warn("x86/bugs: return thunk changed\n");
 

-- 
2.34.1