On 10 January 2018 at 10:09, AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx> 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."
>
> <kicking off kdump after panic>
> 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' attribute were changed
> removing NOMAP bit and they are instead "memblock-reserved".
> * When crash dump kernel boots up, it tries to accesses ACPI tables by
> ioremap'ing them (through acpi_os_ioremap()).
> * Since those regions are not included in device tree's
> "usable-memory-range" and so not recognized as part of crash dump
> kernel's system ram, ioremap() will create a non-cacheable mapping here.
> * ACPI accessor/helper functions are compiled in without unaligned access
> support (ACPI_MISALIGNMENT_NOT_SUPPORTED), eventually ending up a fatal
> panic when accessing ACPI tables.
>
> With this patch, all the reserved memory regions, as well as NOMAP-
> attributed ones which are presumably ACPI runtime code and data, are set
> to be retained in system ram even if they are outside of usable memory
> range specified by device tree blob. Accordingly, ACPI tables are mapped
> as cacheable and can be safely accessed without causing unaligned access
> faults.
>
> Reported-by: Bhupesh Sharma <bhsharma@xxxxxxxxxx>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
> ---
> arch/arm64/mm/init.c | 16 ++++++++++++++--
> 1 file changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 2d5a443b205c..e4a8b64a09b1 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -352,11 +352,23 @@ static void __init fdt_enforce_memory_region(void)
> struct memblock_region reg = {
> .size = 0,
> };
> + u64 idx;
> + phys_addr_t start, end;
>
> of_scan_flat_dt(early_init_dt_scan_usablemem, ®);
>
> - if (reg.size)
> - memblock_cap_memory_range(reg.base, reg.size);
Given that memblock_cap_memory_range() was introduced by you for
kdump, is there any way to handle it there?
If not, should we remove it?
> + if (reg.size) {
> +retry:
> + /* exclude usable & !reserved memory */
> + for_each_free_mem_range(idx, NUMA_NO_NODE, MEMBLOCK_NONE,
> + &start, &end, NULL) {
> + memblock_remove(start, end - start);
> + goto retry;
> + }
> +
> + /* add back fdt's usable memory */
> + memblock_add(reg.base, reg.size);
> + }
> }
>
> void __init arm64_memblock_init(void)
> --
> 2.15.1
>
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