• Ard Biesheuvel's avatar
    efi/arm: Don't mark ACPI reclaim memory as MEMBLOCK_NOMAP · f56ab9a5
    Ard Biesheuvel authored
    
    
    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: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
    Acked-by: Mark Rutland's avatarMark Rutland <mark.rutland@arm.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Matt Fleming <matt@codeblueprint.co.uk>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: linux-efi@vger.kernel.org
    Link: http://lkml.kernel.org/r/20170818194947.19347-2-ard.biesheuvel@linaro.org
    
    
    Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    f56ab9a5