From: Will Deacon <will@kernel.org>
Date: Wed, 10 Jun 2026 10:40:23 +0000 (+0100)
Subject: Revert "arm64: mm: Unmap kernel data/bss entirely from the linear map"
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f102131c842d1e1d95bc7b818ab93944195da7e9;p=thirdparty%2Flinux.git

Revert "arm64: mm: Unmap kernel data/bss entirely from the linear map"

This reverts commit 63e0b6a5b6934d6a919d1c65ea185303200a1874.

Unmapping the kernel '.bss' appears to break KVM initialisation on some
devices, breaking the boot on popular platforms such as RaspberryPi3 and
4.

Revert this change for now so that we can revisit it in future.

Reported-by: Mark Brown <broonie@kernel.org>
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/all/aicVyebkEMs6w6UV@sirena.co.uk
Link: https://lore.kernel.org/r/a1b27e97-182c-485d-a448-56c19c5de2c2@samsung.com
Signed-off-by: Will Deacon <will@kernel.org>
---

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index d68e691c093a5..354bedf0e6386 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -24,7 +24,6 @@
 #include <linux/mm.h>
 #include <linux/vmalloc.h>
 #include <linux/set_memory.h>
-#include <linux/suspend.h>
 #include <linux/kfence.h>
 #include <linux/pkeys.h>
 #include <linux/mm_inline.h>
@@ -1063,29 +1062,6 @@ static void __init __map_memblock(phys_addr_t start, phys_addr_t end,
 				 end - start, prot, early_pgtable_alloc, flags);
 }
 
-static void mark_linear_data_alias_valid(bool valid)
-{
-	set_memory_valid((unsigned long)lm_alias(__init_end),
-			 (unsigned long)(__bss_stop - __init_end) / PAGE_SIZE,
-			 valid);
-}
-
-static int arm64_hibernate_pm_notify(struct notifier_block *nb,
-				     unsigned long mode, void *unused)
-{
-	switch (mode) {
-	default:
-		break;
-	case PM_POST_HIBERNATION:
-		mark_linear_data_alias_valid(false);
-		break;
-	case PM_HIBERNATION_PREPARE:
-		mark_linear_data_alias_valid(true);
-		break;
-	}
-	return 0;
-}
-
 void __init mark_linear_text_alias_ro(void)
 {
 	/*
@@ -1094,21 +1070,6 @@ void __init mark_linear_text_alias_ro(void)
 	update_mapping_prot(__pa_symbol(_text), (unsigned long)lm_alias(_text),
 			    (unsigned long)__init_begin - (unsigned long)_text,
 			    PAGE_KERNEL_RO);
-
-	/*
-	 * Register a PM notifier to remap the linear alias of data/bss as
-	 * valid read-only before hibernation. This is needed because the
-	 * snapshot logic disregards PageReserved pages (such as the ones
-	 * covering the kernel image) unless they are mapped in the linear
-	 * map.
-	 */
-	if (IS_ENABLED(CONFIG_HIBERNATION)) {
-		static struct notifier_block nb = {
-			.notifier_call = arm64_hibernate_pm_notify
-		};
-
-		register_pm_notifier(&nb);
-	}
 }
 
 #ifdef CONFIG_KFENCE
@@ -1238,8 +1199,10 @@ static void __init map_mem(void)
 			       flags);
 	}
 
-	/* Map the kernel data/bss as invalid in the linear map */
-	mark_linear_data_alias_valid(false);
+	/* Map the kernel data/bss read-only in the linear map */
+	__map_memblock(init_end, kernel_end, PAGE_KERNEL_RO, flags);
+	flush_tlb_kernel_range((unsigned long)lm_alias(__init_end),
+			       (unsigned long)lm_alias(__bss_stop));
 }
 
 void mark_rodata_ro(void)