linux-kernel - [RFC PATCH 27/56] x86/mm: Conditionally free alternative sections

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Message-ID: <20251013143444.3999-28-david.kaplan@amd.com>
Date: Mon, 13 Oct 2025 09:34:15 -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 27/56] x86/mm: Conditionally free alternative sections

Keep the alternative related sections, located at the beginning of the
.init section, around if needed.

Signed-off-by: David Kaplan <david.kaplan@....com>
---
 arch/x86/mm/init.c        | 12 ++++++++++--
 arch/x86/mm/mm_internal.h |  2 ++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 8bf6ad4b9400..8dfde4889a09 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -977,8 +977,16 @@ void __ref free_initmem(void)
 
 	mem_encrypt_free_decrypted_mem();
 
-	free_kernel_image_pages("unused kernel image (initmem)",
-				&__init_begin, &__init_end);
+	/*
+	 * __init_alt_end is after the alternative sections in case we need to
+	 * keep that around to support runtime patching.
+	 */
+	if (IS_ENABLED(CONFIG_DYNAMIC_MITIGATIONS))
+		free_kernel_image_pages("unused kernel image (initmem)",
+					&__init_alt_end, &__init_end);
+	else
+		free_kernel_image_pages("unused kernel image (initmem)",
+					&__init_begin, &__init_end);
 }
 
 #ifdef CONFIG_BLK_DEV_INITRD
diff --git a/arch/x86/mm/mm_internal.h b/arch/x86/mm/mm_internal.h
index 097aadc250f7..e961f2257009 100644
--- a/arch/x86/mm/mm_internal.h
+++ b/arch/x86/mm/mm_internal.h
@@ -29,4 +29,6 @@ extern unsigned long tlb_single_page_flush_ceiling;
 void __init x86_numa_init(void);
 #endif
 
+extern void *__init_alt_end;
+
 #endif	/* __X86_MM_INTERNAL_H */
-- 
2.34.1