Re: [PATCH 0/2] arm64: Support to find mirrored memory ranges

[j00447129 <jingxiangfeng@huawei.com>]

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On 2020/2/20 17:21, Ard Biesheuvel wrote:
> On Thu, 20 Feb 2020 at 04:43, Jing Xiangfeng <jingxiangfeng@huawei.com> wrote:
>> This series enable finding mirrored memory ranges
>> functionality on arm64 platform. This feature has been
>> implemented on the x86 platform, so we move some
>> functions from x86.
>>
> Hello Jing Xiangfeng,
>
> Could you explain your use case a bit better? Usually, the firmware is
> a better place to make modifications to the EFI memory map.
>
> The reason I am asking is that currently, on ARM and arm64, we never
> make *any* changes to the firmware provided tables (EFI system table,
> EFI memory map, DT/ACPI/SMBIOS tables etc), in order to ensure that
> kexec is idempotent, i.e., it will always see the exact same state as
> far as the firmware is concerned. This is a bit different from x86,
> where the memory map is already modified for various other reasons, so
> using it for fake memory regions is not such a big deal.
     I am not familiar with the firmware specifications. If we want to 
support
     this functionality now, does it mean that the UEFI spec needs to be 
modified?
     kexec related functions also need to be verified under 
synchronization, right?
>
> Do you see a use case for this in production?
     I'm debugging it by fake memory regions.  Our server is expected to 
support it.

         Thanks for your comments
>
>> Jing Xiangfeng (2):
>>    efi: allow EFI_FAKE_MEMMAP on arm64 platform
>>    arm64/efi: support to find mirrored memory ranges
>>
>>   arch/x86/include/asm/efi.h      |  5 -----
>>   arch/x86/platform/efi/efi.c     | 39 ---------------------------------------
>>   drivers/firmware/efi/Kconfig    |  2 +-
>>   drivers/firmware/efi/arm-init.c |  2 ++
>>   drivers/firmware/efi/efi.c      | 23 +++++++++++++++++++++++
>>   drivers/firmware/efi/memmap.c   | 16 ++++++++++++++++
>>   include/linux/efi.h             |  5 +++++
>>   7 files changed, 47 insertions(+), 45 deletions(-)
>>
>> --
>> 1.8.3.1
>>
> .
>


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