[PATCH] efi: arm: Don't mark ACPI reclaim memory as MEMBLOCK_NOMAP

[Ard Biesheuvel]

On 5 June 2017 at 09:08, Mark Rutland <mark.rutland at arm.com> wrote:
> On Mon, Jun 05, 2017 at 08:04:35AM +0000, Ard Biesheuvel wrote:
>> On ARM, regions of memory that are described by UEFI as having special
>> significance to the firmware itself are omitted from the linear mapping.
>> This is necessary since we cannot guarantee that alternate mappings of
>> the same physical region will use attributes that are compatible with
>> the ones we use for the linear mapping, and aliases with mismatched
>> attributes are prohibited by the architecture.
>>
>> The above does not apply to ACPI reclaim regions: such regions have no
>> special significance to the firmware, and it is up to the OS to decide
>> whether or not to preserve them after it has consumed their contents,
>> and for how long, after which time the OS can use the memory in any way
>> it likes. In the Linux case, such regions are preserved indefinitely,
>> and are simply treated the same way as other 'reserved' memory types.
>>
>> Punching holes into the linear mapping causes page table fragmentation,
>> which increases TLB pressure, and so we should avoid doing so if we can.
>> So add a special case for regions of type EFI_ACPI_RECLAIM_MEMORY, and
>> memblock_reserve() them instead of marking them MEMBLOCK_NOMAP.
>>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>
> Sounds sane to me. FWIW:
>
> Acked-by: Mark Rutland <mark.rutland at arm.com>
>

Thanks.

I have queued this in efi/next