linux-kernel - [RFC PATCH 40/56] x86/alternative: Use sync_core_nmi

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Message-ID: <20251013143444.3999-41-david.kaplan@amd.com>
Date: Mon, 13 Oct 2025 09:34:28 -0500
From: David Kaplan <david.kaplan@....com>
To: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>,
	Peter Zijlstra <peterz@...radead.org>, Josh Poimboeuf <jpoimboe@...nel.org>,
	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, Ingo Molnar
	<mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>,
	<x86@...nel.org>, "H . Peter Anvin" <hpa@...or.com>
CC: Alexander Graf <graf@...zon.com>, Boris Ostrovsky
	<boris.ostrovsky@...cle.com>, <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH 40/56] x86/alternative: Use sync_core_nmi_safe()

Re-patching is done under NMI context so the NMI-safe version of
sync_core() must be used.

Signed-off-by: David Kaplan <david.kaplan@....com>
---
 arch/x86/kernel/alternative.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index b67116ae883c..2d48d750d4d9 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -2585,7 +2585,11 @@ void __init_or_module text_poke_early(void *addr, const void *opcode,
 	} else {
 		local_irq_save(flags);
 		memcpy(addr, opcode, len);
-		sync_core();
+		/* Re-patching occurs in NMI context so we can't do IRET. */
+		if (repatch_in_progress)
+			sync_core_nmi_safe();
+		else
+			sync_core();
 		local_irq_restore(flags);
 
 		/*
-- 
2.34.1