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    SubjectRe: [PATCH 9/9] x86/iommu: use dma_ops_list in get_dma_ops
    On Sun, Sep 28, 2008 at 08:44:24PM +0200, Joerg Roedel wrote:

    > Hmm, we should only call find_dma_ops_for_device() the first time a
    > dma api call is done (look into get_dma_ops). But I also thought
    > about how this lock can be avoided. In the real world it should not
    > be necessary because the dma_ops list is initialized before dma api
    > calls are done. But since there is now a register function which can
    > be called its safer this way. What do you think, are we still safe
    > enough without this lock?

    We could be, if we add a check to the register function that verifies
    it isn't being called after DMAs have started. Something like:

    in register:

    if (dma_started)
    yell loudly

    before PCI device initialization and after IOMMU initialization:
    dma_started = true

    Cheers,
    Muli
    --
    The First Workshop on I/O Virtualization (WIOV '08)
    Dec 2008, San Diego, CA, http://www.usenix.org/wiov08/
    xxx
    SYSTOR 2009---The Israeli Experimental Systems Conference
    http://www.haifa.il.ibm.com/conferences/systor2009/


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