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    SubjectRe: [PATCH 21/22] arm64: replace ZONE_DMA with ZONE_DMA32
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    On 10/01/18 15:55, Christoph Hellwig wrote:
    > On Wed, Jan 10, 2018 at 04:55:17PM +0100, Christoph Hellwig wrote:
    >> On Wed, Jan 10, 2018 at 12:58:14PM +0000, Robin Murphy wrote:
    >>> On 10/01/18 08:09, Christoph Hellwig wrote:
    >>>> arm64 uses ZONE_DMA for allocations below 32-bits. These days we
    >>>> name the zone for that ZONE_DMA32, which will allow to use the
    >>>> dma-direct and generic swiotlb code as-is, so rename it.
    >>>
    >>> I do wonder if we could also "upgrade" GFP_DMA to GFP_DMA32 somehow when
    >>> !ZONE_DMA - there are almost certainly arm64 drivers out there using a
    >>> combination of GFP_DMA and streaming mappings which will no longer get the
    >>> guaranteed 32-bit addresses they expect after this. I'm not sure quite how
    >>> feasible that is, though :/
    >>
    >> I can't find anything obvious in the tree. The alternative would be
    >> to keep ZONE_DMA and set ARCH_ZONE_DMA_BITS.
    >>
    >>> That said, I do agree that this is an appropriate change (the legacy of
    >>> GFP_DMA is obviously horrible), so, provided we get plenty of time to find
    >>> and fix the fallout when it lands:
    >>>
    >>> Reviewed-by: Robin Murphy <robin.murphy@arm.com>
    >>
    >> I was hoping to get this into 4.15. What would be proper time to
    >> fix the fallout?
    >
    > Err, 4.16 of course.

    Hee hee - cramming it into 4.15 is exactly what I wouldn't want to do,
    even if Linus would accept it :)

    Landing it this merge window for 4.16-rc1 sounds good if we can manage that.

    Robin.

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