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    SubjectRe: [PATCH] Containment measures for slab objects on scatter gather lists
    > DMA to or from memory should be done via the DMA mapping API.  If we're
    > DMAing to/from a limited range within a page, either we should be using
    > dma_map_single(), or dma_map_page() with an appropriate offset and size.

    If those ranges overlap a cache line then the dma mapping API will not
    save your backside.

    On a system with a 32 byte cache granularity what happens if you get two
    dma mapping calls for x and x+16. Right now the thing that avoids this
    occurring is that the allocators don't pack stuff in that hard so x+16
    always belongs to the same driver and we can hope driver authors are

    > sizes, but they do happen. We handle this on ARM by writing back
    > the overlapped lines and invalidating the rest before the DMA operation
    > commences, and hope that the overlapped lines aren't touched for the
    > duration of the DMA.)

    The combination of "hope" and "DMA" isn't a good one for stable system
    design. In this situation we should be waving large red flags
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      Last update: 2007-06-30 01:09    [W:0.029 / U:4.504 seconds]
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