[PATCH v3.1 0/4] arm64: kexec, kdump: fix boot failures on acpi-only system

[rruigrok@codeaurora.org (Richard Ruigrok)]

Hi Akashi,

On 7/9/2018 5:42 PM, AKASHI Takahiro wrote:
> This patch series is a set of bug fixes to address kexec/kdump
> failures which are sometimes observed on ACPI-only system and reported
> in LAK-ML before.
>
> In short, the phenomena are:
> 1. kexec'ed kernel can fail to boot because some ACPI table is corrupted
>    by a new kernel (or other data) being loaded into System RAM. Currently
>    kexec may possibly allocate space ignoring such "reserved" regions.
>    We will see no messages after "Bye!"
>
> 2. crash dump (kdump) kernel can fail to boot and get into panic due to
>    an alignment fault when accessing ACPI tables. This can happen because
>    those tables are not always properly aligned while they are mapped
>    non-cacheable (ioremap'ed) as they are not recognized as part of System
>    RAM under the current implementation.
>
> After discussing several possibilities to address those issues,
> the agreed approach, in my understanding, is
> * to add resource entries for every "reserved", i.e. memblock_reserve(),
>   regions to /proc/iomem.
>   (NOMAP regions, also marked as "reserved," remains at top-level for
>   backward compatibility. User-space can tell the difference between
>   reserved-system-ram and reserved-address-space.)
> * For case (1), user space (kexec-tools) should rule out such regions
>   in searching for free space for loaded data.
> * For case (2), the kernel should access ACPI tables by mapping
>   them with appropriate memory attributes described in UEFI memory map.
>   (This means that it doesn't require any changes in /proc/iomem, and
>   hence user space.)
>
> Please find past discussions about /proc/iomem in [1].
> --- more words from James ---
> Our attempts to fix this just in the kernel reached a dead end, because Kdump
> needs to include reserved-system-ram, whereas kexec has to avoid it. User-space
> needs to be able to tell reserved-system-ram and reserved-address-space apart.
> Hence we need to expose that information, and pick it up in user-space.
>
> Patched-kernel and unpatch-user-space will work the same way it does today, as
> the additional reserved regions are ignored by user-space.
>
> Unpatched-kernel and patched-user-space will also work the same way it does
> today as the additional reserved regions are missing.
> --->8---
>
> Patch#1 addresses kexec case, for which you are also required to update
> user space. See necessary patches in [2]. If you want to review Patch#1,
> please also take a look at and review [2].
>
> Patch#2, #3 and #4 address the kdump case above.
>
>
> Changes in v3.1 (2018, July 10, 2018)
> * add Ard's patch[4] to this patch set
>
> Changes in v3 (2018, July 9, 2018)
> * drop the v2's patch#3, preferring [4]
>
> Changes in v2 (2018, June 19, 2018)
> * re-organise v1's patch#2 and #3 into v2's #2, #3 and #4
>   not to break bisect
>
> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2018-March/565980.html
> [2] https://git.linaro.org/people/takahiro.akashi/kexec-tools.git arm64/resv_mem
> [3] http://lists.infradead.org/pipermail/linux-arm-kernel/2018-April/573655.html
> [4] https://marc.info/?l=linux-efi&m=152930773507524&w=2
>
> AKASHI Takahiro (2):
>   efi/arm: map UEFI memory map even w/o runtime services enabled
>   arm64: acpi: fix alignment fault in accessing ACPI
>
> Ard Biesheuvel (1):
>   efi/arm: preserve early mapping of UEFI memory map longer for BGRT
>
> James Morse (1):
>   arm64: export memblock_reserve()d regions via /proc/iomem
>
>  arch/arm64/include/asm/acpi.h      | 23 ++++++++++++------
>  arch/arm64/kernel/acpi.c           | 11 +++------
>  arch/arm64/kernel/setup.c          | 38 ++++++++++++++++++++++++++++++
>  drivers/firmware/efi/arm-init.c    |  1 -
>  drivers/firmware/efi/arm-runtime.c | 16 +++++++------
>  5 files changed, 66 insertions(+), 23 deletions(-)
>
Please add my tested-by <rruigrok@codeaurora.org>

Tested this patch series on top of v4.17 on Centriq ARM64 system with the kexec-tool as specified : https://git.linaro.org/people/takahiro.akashi/kexec-tools.git? branch arm64/resv_mem
Prior to this patch set and Kexec tool update, we were seeing the ESRT region being over-written, it showed as a mangled region in a kexec'ed kernel.
- ex: [??? 0.000000] esrt: Unsupported ESRT version 5681331550117508106.
With this patchset and tool upadate, the ESRT region appears correct
[??? 0.000000] esrt: Reserving ESRT space from 0x000000000b6c8d18 to 0x000000000b6c8df0.

Thanks for fixing this!
Richard

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