[lkml]   [2002]   [Jun]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: PCI DMA to small buffers on cache-incoherent arch
    >>>>> "David" == David S Miller <> writes:

    Paul> This is the problem scenario. Suppose we are doing DMA to a
    Paul> buffer B and also independently accessing a variable X which
    Paul> is not part of B. Suppose that X and the beginning of B are
    Paul> both in cache line C.

    David> I see what the problem is. Hmmm...

    David> I'm trying to specify this such that knowledge of
    David> cachelines and whatnot don't escape the arch specific code,
    David> ho hum... Looks like that isn't possible.

    So is the consensus now that in general drivers should make sure any
    buffers passed to pci_map/unmap are aligned to SMP_CACHE_BYTES (and a
    multiple of SMP_CACHE_BYTES in size)? In other words if a driver uses
    an unaligned buffer it should be fixed unless we can prove (and
    document in a comment :) that it won't cause problems on an arch
    without cache coherency and with a writeback cache.

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2005-03-22 13:26    [W:0.046 / U:5.416 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site