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    SubjectRe: [PATCH v2 4/4] arm64: acpi: fix alignment fault in accessing ACPI
    On 19 June 2018 at 08:44, AKASHI Takahiro <takahiro.akashi@linaro.org> wrote:
    > 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>

    Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

    > ---
    > 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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