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    SubjectRe: [PATCH 0/3] x86: restore old GART alloc_coherent
    On Wed, Sep 24, 2008 at 08:48:34PM +0900, FUJITA Tomonori wrote:
    > This pachset is against tip/iommu.
    >
    > What this patchset does is restoring old GART alloc_coherent behavior
    > (before the alloc_coherent rewrite):
    >
    > http://lkml.org/lkml/2008/8/12/200
    >
    > Currently, GART alloc_coherent tries to allocate pages with GFP_DMA32
    > for a device having dma_masks > 24bit < 32bits. If GART gets an
    > address that a device can't access to, GART tries to map the address
    > to a virtual I/O address that the device can access to.
    >
    > But Andi pointed out, "The GART is somewhere in the 4GB range so you
    > cannot use it to map anything < 4GB. Also GART is pretty small."
    >
    > http://lkml.org/lkml/2008/9/12/43
    >
    > So it's possible that GART doesn't have virtual I/O address space that
    > a device can access to. The current behavior might not work for a
    > device having dma_masks > 24bit < 32bits. This patchset restores old
    > GART alloc_coherent behavior, which doesn't use GART hardware (if an
    > user doesn't enable force_iommu option).

    Acked-by: Joerg Roedel <joerg.roedel@amd.com>

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