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    Subject[PATCH v2 4/4] arm64: acpi: fix alignment fault in accessing ACPI
    Date
    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)
    (snip...)
    Bye!
    (snip...)
    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
    (snip...)
    Process swapper/0 (pid: 0, stack limit = 0xffff000008cc0000)
    Call trace:
    (snip...)
    [<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..

    (diagnosis)
    * 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 <takahiro.akashi@linaro.org>
    Suggested-by: James Morse <james.morse@arm.com>
    Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
    Reported-by and Tested-by: Bhupesh Sharma <bhsharma@redhat.com>
    ---
    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 */
    #ifdef CONFIG_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 */

    #ifdef CONFIG_ACPI_NUMA
    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>

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

    -#ifdef CONFIG_ACPI_APEI
    -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);
    }
    -#endif
    --
    2.17.0
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