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    SubjectRe: [PATCH 0/6] get rid of on-stack dma buffers
    From: James Bottomley <>
    Date: Tue, 22 Mar 2011 08:35:04 -0500

    > The API will round up so that the correct region covers the API.
    > However, if you have other structures packed into the space (as very
    > often happens on stack), you get cache line interference in the CPU if
    > they get accessed: The act of accessing an adjacent object pulls in
    > cache above your object and destroys DMA coherence. This is the
    > principle reason why DMA to stack is a bad idea.

    Another major real reason we can't DMA on-stack stuff is because the
    stack is mapped virtually on some platforms.

    And that is the original reason the restriction was put in place.

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      Last update: 2011-03-22 21:17    [W:0.018 / U:2.160 seconds]
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