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Subject[PATCH v3 3/3] arm64: acpi: fix alignment fault in accessing ACPI
This is a fix against the issue that crash dump kernel may hang up
during booting, which can happen on any ACPI-based system with "ACPI
Reclaim Memory."

(kernel messages after panic kicked off kdump)
ACPI: Core revision 20170728
pud=000000002e7d0003, *pmd=000000002e7c0003, *pte=00e8000039710707
Internal error: Oops: 96000021 [#1] SMP
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.14.0-rc6 #1
task: ffff000008d05180 task.stack: ffff000008cc0000
PC is at acpi_ns_lookup+0x25c/0x3c0
LR is at acpi_ds_load1_begin_op+0xa4/0x294
Process swapper/0 (pid: 0, stack limit = 0xffff000008cc0000)
Call trace:
[<ffff0000084a6764>] acpi_ns_lookup+0x25c/0x3c0
[<ffff00000849b4f8>] acpi_ds_load1_begin_op+0xa4/0x294
[<ffff0000084ad4ac>] acpi_ps_build_named_op+0xc4/0x198
[<ffff0000084ad6cc>] acpi_ps_create_op+0x14c/0x270
[<ffff0000084acfa8>] acpi_ps_parse_loop+0x188/0x5c8
[<ffff0000084ae048>] acpi_ps_parse_aml+0xb0/0x2b8
[<ffff0000084a8e10>] acpi_ns_one_complete_parse+0x144/0x184
[<ffff0000084a8e98>] acpi_ns_parse_table+0x48/0x68
[<ffff0000084a82cc>] acpi_ns_load_table+0x4c/0xdc
[<ffff0000084b32f8>] acpi_tb_load_namespace+0xe4/0x264
[<ffff000008baf9b4>] acpi_load_tables+0x48/0xc0
[<ffff000008badc20>] acpi_early_init+0x9c/0xd0
[<ffff000008b70d50>] start_kernel+0x3b4/0x43c
Code: b9008fb9 2a000318 36380054 32190318 (b94002c0)
---[ end trace c46ed37f9651c58e ]---
Kernel panic - not syncing: Fatal exception
Rebooting in 10 seconds..

* This fault is a data abort, alignment fault (ESR=0x96000021)
during reading out ACPI table.
* Initial ACPI tables are normally stored in system ram and marked as
"ACPI Reclaim memory" by the firmware.
* After the commit f56ab9a5b73c ("efi/arm: Don't mark ACPI reclaim
memory as MEMBLOCK_NOMAP"), those regions are differently handled
as they are "memblock-reserved", without NOMAP bit.
* So they are now excluded from device tree's "usable-memory-range"
which kexec-tools determines based on a current view of /proc/iomem.
* When crash dump kernel boots up, it tries to accesses ACPI tables by
mapping them with ioremap(), not ioremap_cache(), in acpi_os_ioremap()
since they are no longer part of mapped system ram.
* Given that ACPI accessor/helper functions are compiled in without
unaligned access support (ACPI_MISALIGNMENT_NOT_SUPPORTED),
any unaligned access to ACPI tables can cause a fatal panic.

With this patch, acpi_os_ioremap() always honors memory attribute
information provided by the firmware (EFI) and retaining cacheability
allows the kernel safe access to ACPI tables.

Signed-off-by: AKASHI Takahiro <>
Reviewed-by: James Morse <>
Reviewed-by: Ard Biesheuvel <>
Reported-by and Tested-by: Bhupesh Sharma <>
arch/arm64/include/asm/acpi.h | 23 ++++++++++++++++-------
arch/arm64/kernel/acpi.c | 11 +++--------
2 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
index 0db62a4cbce2..68bc18cb2b85 100644
--- a/arch/arm64/include/asm/acpi.h
+++ b/arch/arm64/include/asm/acpi.h
@@ -12,10 +12,12 @@
#ifndef _ASM_ACPI_H
#define _ASM_ACPI_H

+#include <linux/efi.h>
#include <linux/memblock.h>
#include <linux/psci.h>

#include <asm/cputype.h>
+#include <asm/io.h>
#include <asm/smp_plat.h>
#include <asm/tlbflush.h>

@@ -29,18 +31,22 @@

/* Basic configuration for ACPI */
+pgprot_t __acpi_get_mem_attribute(phys_addr_t addr);
/* ACPI table mapping after acpi_permanent_mmap is set */
static inline void __iomem *acpi_os_ioremap(acpi_physical_address phys,
acpi_size size)
+ /* For normal memory we already have a cacheable mapping. */
+ if (memblock_is_map_memory(phys))
+ return (void __iomem *)__phys_to_virt(phys);
- * EFI's reserve_regions() call adds memory with the WB attribute
- * to memblock via early_init_dt_add_memory_arch().
+ * We should still honor the memory's attribute here because
+ * crash dump kernel possibly excludes some ACPI (reclaim)
+ * regions from memblock list.
- if (!memblock_is_memory(phys))
- return ioremap(phys, size);
- return ioremap_cache(phys, size);
+ return __ioremap(phys, size, __acpi_get_mem_attribute(phys));
#define acpi_os_ioremap acpi_os_ioremap

@@ -129,7 +135,10 @@ static inline const char *acpi_get_enable_method(int cpu)
* for compatibility.
#define acpi_disable_cmcff 1
-pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr);
+static inline pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr)
+ return __acpi_get_mem_attribute(addr);
#endif /* CONFIG_ACPI_APEI */

diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index 7b09487ff8fb..ed46dc188b22 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c
@@ -18,6 +18,7 @@
#include <linux/acpi.h>
#include <linux/bootmem.h>
#include <linux/cpumask.h>
+#include <linux/efi.h>
#include <linux/efi-bgrt.h>
#include <linux/init.h>
#include <linux/irq.h>
@@ -29,13 +30,9 @@

#include <asm/cputype.h>
#include <asm/cpu_ops.h>
+#include <asm/pgtable.h>
#include <asm/smp_plat.h>

-# include <linux/efi.h>
-# include <asm/pgtable.h>
int acpi_noirq = 1; /* skip ACPI IRQ initialization */
int acpi_disabled = 1;
@@ -239,8 +236,7 @@ void __init acpi_boot_table_init(void)

-pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr)
+pgprot_t __acpi_get_mem_attribute(phys_addr_t addr)
* According to "Table 8 Map: EFI memory types to AArch64 memory
@@ -261,4 +257,3 @@ pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr)
return __pgprot(PROT_NORMAL_NC);
return __pgprot(PROT_DEVICE_nGnRnE);
 \ /
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