On 8 November 2018 at 20:13, Bhupesh Sharma <bhsha...@redhat.com> wrote:
> Hi Ard,
>
> On Wed, Nov 7, 2018 at 7:46 PM Ard Biesheuvel <ard.biesheu...@linaro.org> 
> wrote:
>>
>> This series addresses the kexec/kdump crash on arm64 system with many CPUs
>> that was reported by Bhupesh.
>>
>> Patch #1 fixes the actual crash, but may result in memblock_reserve() to
>> fail. This is fixed in patch #4, where the point that the persistent
>> reservations are applied is moved to after memblock_allow_resize() has
>> been called.
>>
>> Patches #2 and #3 contain some minor preparatory changes that are
>> required on ARM to ensure that efi_apply_persistent_mem_reservations()
>> can be called at some point (i.e., when memblock resizing is already
>> permitted and early memremap() is still usable)
>>
>> Patches #5 and #6 optimize the EFI persistent memreserve infrastructure
>> so that fewer memblock reservations are required.
>>
>> Changes since v1:
>> - Russell pointed out that switching to ordinary memremap() was not
>>   possible this early, and so I refactored the ARM early boot code
>>   slightly so that we can keep using early_memremap().
>>
>> Ard Biesheuvel (6):
>>   arm64: memblock: don't permit memblock resizing until linear mapping
>>     is up
>>   ARM: mm: permit memblock resizing right after mapping the linear
>>     region
>>   ARM: mm: permit early_memremap() to be used in paging_init()
>>   efi/arm: defer persistent reservations until after paging_init()
>>   efi: permit multiple entries in persistent memreserve data structure
>>   efi: reduce the amount of memblock reservations for persistent
>>     allocations
>>
>>  arch/arm/kernel/setup.c                 |  2 -
>>  arch/arm/mm/init.c                      |  1 -
>>  arch/arm/mm/mmu.c                       |  5 ++
>>  arch/arm64/kernel/setup.c               |  1 +
>>  arch/arm64/mm/init.c                    |  2 -
>>  arch/arm64/mm/mmu.c                     |  2 +
>>  drivers/firmware/efi/efi.c              | 59 ++++++++++++++------
>>  drivers/firmware/efi/libstub/arm-stub.c |  2 +-
>>  include/linux/efi.h                     | 23 +++++++-
>>  9 files changed, 72 insertions(+), 25 deletions(-)
>>
>> --
>> 2.19.1
>>
>
> I did some quick checks (as I just returned from my holidays and got
> hold of the hardware just now) and I haven't had the opportunity to
> look closely at the entire patch set, but it looks like a step in the
> right direction especially as we try to have fewer memblock
> reservations (I will have a closer look at the patchset perhaps over
> the weekend).
>
> I tested this on the hardware (with 224 CPUs) where I was seeing the
> crash initially and kdump seems to work fine on the same. Here are
> some kdump kernel logs with 'memblock=debug' set in bootargs:
>
> [    0.000000] memblock_reserve:
> [0x00000000e2e02e18-0x00000000e2e02e4f] efi_mem_reserve+0x3c/0x54
> [    0.000000] memblock_reserve:
> [0x00000000dac70000-0x00000000dac7ffff] efi_init+0xc4/0x17c
> [    0.000000] memblock_remove:
> [0x0001000000000000-0x0000fffffffffffe] arm64_memblock_init+0x6c/0x418
> [    0.000000] memblock_remove:
> [0x0000800080000000-0x000080007ffffffe] arm64_memblock_init+0xac/0x418
> [    0.0001dd0000-0x00000000a2cfffff] arm64_memblock_init+0x184/0x418
> [    0.000000] memblock_add: [0x00000000a1dd0000-0x00000000a2cfffff]
> arm64_memblock_init+0x190/0x418
> [    0.000000] memblock_reserve:
> [0x00000000a1dd0000-0x00000000a2cfffff]
> arm64_memblock_init+0x19c/0x418
> [    0.000000] memblock_reserve:
> [0x00000000a0080000-0x00000000a1dcffff]
> arm64_memblock_init+0x1f8/0x418
> [    0.000000] memblock_reserve:
> [0x00000000a1dd0000-0x00000000a2cfb402]     0.000000]
> memblock_reserve: [0x00000000bfff0000-0x00000000bfff33ff]
> arm64_memblock_init+0x3b4/0x418
> [    0.000000] Reserving 13KB of memory at 0xbfff0000 for elfcorehdr
> [    0.000000] memblock_reserve:
> [0x00000000bffe0000-0x00000000bffeffff]
> memblock_alloc_base_nid+0x70/0x8c
> [    0.000000] memblock_reserve:
> [0x00000000bffd0000-0x00000000bffdffff]
> memblock_alloc_base_nid+0x70/0x8c
> [    0.000000] memblock_reserve: [0x00000000bffc0se_nid+0x70/0x8c
> [    0.000000] memblock_reserve:
> [0x00000000bffb0000-0x00000000bffbffff]
> memblock_alloc_base_nid+0x70/0x8c
> [    0.000000]    memblock_free:
> [0x00000000a1d80000-0x00000000a1dcffff] paging_init+0x6d4/0x6fc
> [    0.000000] memblock_reserve:
> [0x00000000ddab9e18-0x00000000ddab9e27]
> efi_apply_persistent_mem_reservations+0x8c/0xbc
>
> So, things look great so far. So, please feel free to add:
> Tested-by: Bhupesh Sharma <bhsha...@redhat.com>
>

Thanks!

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