Re: [PATCH v2] x86: remove the BIOS memory corruption check feature

[H. Peter Anvin]

On July 20, 2026 1:41:05 PM PDT, Luiz Capitulino <luizcap@xxxxxxxxxx> wrote:
>By default, the BIOS memory corruption check works by reserving the
>first 64 KiB physical area from memblock, zeroing it and then scanning it
>periodically.
>
>However, this functionality has been broken since v5.13 by two commits:
>
>- Commit a799c2bd29d1 ("x86/setup: Consolidate early memory reservations").
>  Moved trim_low_memory_range() into early_reserve_memory(), which runs
>  earlier in setup_arch(), causing the first 64 KiB to be reserved (when
>  CONFIG_X86_RESERVE_LOW=64) before setup_bios_corruption_check() runs
>
>- Commit f1d4d47c5851 ("x86/setup: Always reserve the first 1M of RAM").
>  Hardcodes the reservation of the first 64 KiB early in
>  early_reserve_memory()
>
>It might be possible to get this feature to work by allowing
>setup_bios_corruption_check() to run first, but it's just not worth it
>given that the kernel will never access this memory area anyways.
>
>Signed-off-by: Luiz Capitulino <luizcap@xxxxxxxxxx>
>---
>
>Changelog
>=========
>
>v2
>- Rebase against latest Linus tree (v7.2-rc4)
>- Improve changelog
>
> .../admin-guide/kernel-parameters.txt         |  23 ---
> arch/x86/Kconfig                              |  30 ---
> arch/x86/configs/i386_defconfig               |   1 -
> arch/x86/configs/x86_64_defconfig             |   1 -
> arch/x86/include/asm/bios_ebda.h              |  17 --
> arch/x86/include/asm/setup.h                  |   1 -
> arch/x86/kernel/Makefile                      |   2 -
> arch/x86/kernel/check.c                       | 187 ------------------
> arch/x86/kernel/setup.c                       |   4 -
> 9 files changed, 266 deletions(-)
> delete mode 100644 arch/x86/kernel/check.c
>
>diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>index b5493a7f8f22..314a2a0dc9cd 100644
>--- a/Documentation/admin-guide/kernel-parameters.txt
>+++ b/Documentation/admin-guide/kernel-parameters.txt
>@@ -3935,29 +3935,6 @@ Kernel parameters
> 			specified as e820 types, e.g., 1 = RAM, 2 = reserved,
> 			3 = ACPI, 12 = PRAM.
> -	memory_corruption_check=0/1 [X86,EARLY]
>-			Some BIOSes seem to corrupt the first 64k of
>-			memory when doing things like suspend/resume.
>-			Setting this option will scan the memory
>-			looking for corruption.  Enabling this will
>-			both detect corruption and prevent the kernel
>-			from using the memory being corrupted.
>-			However, it's intended as a diagnostic tool; if
>-			repeatable BIOS-originated corruption always
>-			affects the same memory, you can use memmap=
>-			to prevent the kernel from using that memory.
>-
>-	memory_corruption_check_size=size [X86,EARLY]
>-			By default it checks for corruption in the low
>-			64k, making this memory unavailable for normal
>-			use.  Use this parameter to scan for
>-			corruption in more or less memory.
>-
>-	memory_corruption_check_period=seconds [X86,EARLY]
>-			By default it checks for corruption every 60
>-			seconds.  Use this parameter to check at some
>-			other rate.  0 disables periodic checking.
>-
> 	memory_hotplug.memmap_on_memory
> 			[KNL,X86,ARM] Boolean flag to enable this feature.
> 			Format: {on | off (default)}
>diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>index bdad90f210e4..cce558ca5c6c 100644
>--- a/arch/x86/Kconfig
>+++ b/arch/x86/Kconfig
>@@ -1601,36 +1601,6 @@ config X86_PMEM_LEGACY
>  	  Say Y if unsure.
> -config X86_CHECK_BIOS_CORRUPTION
>-	bool "Check for low memory corruption"
>-	help
>-	  Periodically check for memory corruption in low memory, which
>-	  is suspected to be caused by BIOS.  Even when enabled in the
>-	  configuration, it is disabled at runtime.  Enable it by
>-	  setting "memory_corruption_check=1" on the kernel command
>-	  line.  By default it scans the low 64k of memory every 60
>-	  seconds; see the memory_corruption_check_size and
>-	  memory_corruption_check_period parameters in
>-	  Documentation/admin-guide/kernel-parameters.rst to adjust this.
>-
>-	  When enabled with the default parameters, this option has
>-	  almost no overhead, as it reserves a relatively small amount
>-	  of memory and scans it infrequently.  It both detects corruption
>-	  and prevents it from affecting the running system.
>-
>-	  It is, however, intended as a diagnostic tool; if repeatable
>-	  BIOS-originated corruption always affects the same memory,
>-	  you can use memmap= to prevent the kernel from using that
>-	  memory.
>-
>-config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
>-	bool "Set the default setting of memory_corruption_check"
>-	depends on X86_CHECK_BIOS_CORRUPTION
>-	default y
>-	help
>-	  Set whether the default state of memory_corruption_check is
>-	  on or off.
>-
> config MTRR
> 	def_bool y
> 	prompt "MTRR (Memory Type Range Register) support" if EXPERT
>diff --git a/arch/x86/configs/i386_defconfig b/arch/x86/configs/i386_defconfig
>index 79fa38ca954d..848c2d924668 100644
>--- a/arch/x86/configs/i386_defconfig
>+++ b/arch/x86/configs/i386_defconfig
>@@ -36,7 +36,6 @@ CONFIG_PARAVIRT=y
> CONFIG_X86_REROUTE_FOR_BROKEN_BOOT_IRQS=y
> CONFIG_X86_MSR=y
> CONFIG_X86_CPUID=y
>-CONFIG_X86_CHECK_BIOS_CORRUPTION=y
> # CONFIG_MTRR_SANITIZER is not set
> CONFIG_EFI=y
> CONFIG_EFI_STUB=y
>diff --git a/arch/x86/configs/x86_64_defconfig b/arch/x86/configs/x86_64_defconfig
>index 269f7d808be4..e05d67f708cb 100644
>--- a/arch/x86/configs/x86_64_defconfig
>+++ b/arch/x86/configs/x86_64_defconfig
>@@ -35,7 +35,6 @@ CONFIG_X86_REROUTE_FOR_BROKEN_BOOT_IRQS=y
> CONFIG_X86_MSR=y
> CONFIG_X86_CPUID=y
> CONFIG_NUMA=y
>-CONFIG_X86_CHECK_BIOS_CORRUPTION=y
> # CONFIG_MTRR_SANITIZER is not set
> CONFIG_EFI=y
> CONFIG_EFI_STUB=y
>diff --git a/arch/x86/include/asm/bios_ebda.h b/arch/x86/include/asm/bios_ebda.h
>index 4d5a17e2febe..2f441fd9ebf8 100644
>--- a/arch/x86/include/asm/bios_ebda.h
>+++ b/arch/x86/include/asm/bios_ebda.h
>@@ -20,21 +20,4 @@ static inline unsigned int get_bios_ebda(void)
>  void reserve_bios_regions(void);
> -#ifdef CONFIG_X86_CHECK_BIOS_CORRUPTION
>-/*
>- * This is obviously not a great place for this, but we want to be
>- * able to scatter it around anywhere in the kernel.
>- */
>-void check_for_bios_corruption(void);
>-void start_periodic_check_for_corruption(void);
>-#else
>-static inline void check_for_bios_corruption(void)
>-{
>-}
>-
>-static inline void start_periodic_check_for_corruption(void)
>-{
>-}
>-#endif
>-
> #endif /* _ASM_X86_BIOS_EBDA_H */
>diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
>index 914eb32581c7..1f58361eb038 100644
>--- a/arch/x86/include/asm/setup.h
>+++ b/arch/x86/include/asm/setup.h
>@@ -42,7 +42,6 @@ static inline void vsmp_init(void) { }
>  struct pt_regs;
> -void setup_bios_corruption_check(void);
> void early_platform_quirks(void);
>  extern unsigned long saved_video_mode;
>diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
>index 31f46fd00527..702536938433 100644
>--- a/arch/x86/kernel/Makefile
>+++ b/arch/x86/kernel/Makefile
>@@ -149,8 +149,6 @@ obj-$(CONFIG_JAILHOUSE_GUEST)	+= jailhouse.o
> obj-$(CONFIG_EISA)		+= eisa.o
> obj-$(CONFIG_PCSPKR_PLATFORM)	+= pcspeaker.o
> -obj-$(CONFIG_X86_CHECK_BIOS_CORRUPTION) += check.o
>-
> obj-$(CONFIG_OF)			+= devicetree.o
> obj-$(CONFIG_UPROBES)			+= uprobes.o
> diff --git a/arch/x86/kernel/check.c b/arch/x86/kernel/check.c
>deleted file mode 100644
>index 5136e6818da8..000000000000
>--- a/arch/x86/kernel/check.c
>+++ /dev/null
>@@ -1,187 +0,0 @@
>-// SPDX-License-Identifier: GPL-2.0
>-
>-#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>-
>-#include <linux/init.h>
>-#include <linux/sched.h>
>-#include <linux/kthread.h>
>-#include <linux/workqueue.h>
>-#include <linux/memblock.h>
>-
>-#include <asm/proto.h>
>-#include <asm/setup.h>
>-
>-/*
>- * Some BIOSes seem to corrupt the low 64k of memory during events
>- * like suspend/resume and unplugging an HDMI cable.  Reserve all
>- * remaining free memory in that area and fill it with a distinct
>- * pattern.
>- */
>-#define MAX_SCAN_AREAS	8
>-
>-static int __read_mostly memory_corruption_check = -1;
>-
>-static unsigned __read_mostly corruption_check_size = 64*1024;
>-static unsigned __read_mostly corruption_check_period = 60; /* seconds */
>-
>-static struct scan_area {
>-	u64 addr;
>-	u64 size;
>-} scan_areas[MAX_SCAN_AREAS];
>-static int num_scan_areas;
>-
>-static __init int set_corruption_check(char *arg)
>-{
>-	ssize_t ret;
>-	unsigned long val;
>-
>-	if (!arg) {
>-		pr_err("memory_corruption_check config string not provided\n");
>-		return -EINVAL;
>-	}
>-
>-	ret = kstrtoul(arg, 10, &val);
>-	if (ret)
>-		return ret;
>-
>-	memory_corruption_check = val;
>-
>-	return 0;
>-}
>-early_param("memory_corruption_check", set_corruption_check);
>-
>-static __init int set_corruption_check_period(char *arg)
>-{
>-	ssize_t ret;
>-	unsigned long val;
>-
>-	if (!arg) {
>-		pr_err("memory_corruption_check_period config string not provided\n");
>-		return -EINVAL;
>-	}
>-
>-	ret = kstrtoul(arg, 10, &val);
>-	if (ret)
>-		return ret;
>-
>-	corruption_check_period = val;
>-	return 0;
>-}
>-early_param("memory_corruption_check_period", set_corruption_check_period);
>-
>-static __init int set_corruption_check_size(char *arg)
>-{
>-	char *end;
>-	unsigned size;
>-
>-	if (!arg) {
>-		pr_err("memory_corruption_check_size config string not provided\n");
>-		return -EINVAL;
>-	}
>-
>-	size = memparse(arg, &end);
>-
>-	if (*end == '\0')
>-		corruption_check_size = size;
>-
>-	return (size == corruption_check_size) ? 0 : -EINVAL;
>-}
>-early_param("memory_corruption_check_size", set_corruption_check_size);
>-
>-
>-void __init setup_bios_corruption_check(void)
>-{
>-	phys_addr_t start, end;
>-	u64 i;
>-
>-	if (memory_corruption_check == -1) {
>-		memory_corruption_check =
>-#ifdef CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
>-			1
>-#else
>-			0
>-#endif
>-			;
>-	}
>-
>-	if (corruption_check_size == 0)
>-		memory_corruption_check = 0;
>-
>-	if (!memory_corruption_check)
>-		return;
>-
>-	corruption_check_size = round_up(corruption_check_size, PAGE_SIZE);
>-
>-	for_each_free_mem_range(i, NUMA_NO_NODE, MEMBLOCK_NONE, &start, &end,
>-				NULL) {
>-		start = clamp_t(phys_addr_t, round_up(start, PAGE_SIZE),
>-				PAGE_SIZE, corruption_check_size);
>-		end = clamp_t(phys_addr_t, round_down(end, PAGE_SIZE),
>-			      PAGE_SIZE, corruption_check_size);
>-		if (start >= end)
>-			continue;
>-
>-		memblock_reserve(start, end - start);
>-		scan_areas[num_scan_areas].addr = start;
>-		scan_areas[num_scan_areas].size = end - start;
>-
>-		/* Assume we've already mapped this early memory */
>-		memset(__va(start), 0, end - start);
>-
>-		if (++num_scan_areas >= MAX_SCAN_AREAS)
>-			break;
>-	}
>-
>-	if (num_scan_areas)
>-		pr_info("Scanning %d areas for low memory corruption\n", num_scan_areas);
>-}
>-
>-
>-static void check_for_bios_corruption(void)
>-{
>-	int i;
>-	int corruption = 0;
>-
>-	if (!memory_corruption_check)
>-		return;
>-
>-	for (i = 0; i < num_scan_areas; i++) {
>-		unsigned long *addr = __va(scan_areas[i].addr);
>-		unsigned long size = scan_areas[i].size;
>-
>-		for (; size; addr++, size -= sizeof(unsigned long)) {
>-			if (!*addr)
>-				continue;
>-			pr_err("Corrupted low memory at %p (%lx phys) = %08lx\n", addr, __pa(addr), *addr);
>-			corruption = 1;
>-			*addr = 0;
>-		}
>-	}
>-
>-	WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n");
>-}
>-
>-static void check_corruption(struct work_struct *dummy);
>-static DECLARE_DELAYED_WORK(bios_check_work, check_corruption);
>-
>-static void check_corruption(struct work_struct *dummy)
>-{
>-	check_for_bios_corruption();
>-	schedule_delayed_work(&bios_check_work,
>-		round_jiffies_relative(corruption_check_period*HZ));
>-}
>-
>-static int start_periodic_check_for_corruption(void)
>-{
>-	if (!num_scan_areas || !memory_corruption_check || corruption_check_period == 0)
>-		return 0;
>-
>-	pr_info("Scanning for low memory corruption every %d seconds\n", corruption_check_period);
>-
>-	/* First time we run the checks right away */
>-	schedule_delayed_work(&bios_check_work, 0);
>-
>-	return 0;
>-}
>-device_initcall(start_periodic_check_for_corruption);
>-
>diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
>index 46882ce79c3a..ec2cbe3f800d 100644
>--- a/arch/x86/kernel/setup.c
>+++ b/arch/x86/kernel/setup.c
>@@ -1096,10 +1096,6 @@ void __init setup_arch(char **cmdline_p)
> 	/* preallocate 4k for mptable mpc */
> 	e820__memblock_alloc_reserved_mpc_new();
> -#ifdef CONFIG_X86_CHECK_BIOS_CORRUPTION
>-	setup_bios_corruption_check();
>-#endif
>-
> #ifdef CONFIG_X86_32
> 	printk(KERN_DEBUG "initial memory mapped: [mem 0x00000000-%#010lx]\n",
> 			(max_pfn_mapped<<PAGE_SHIFT) - 1);

Acked-by: H. Peter Anvin <hpa@xxxxxxxxx>