From mboxrd@z Thu Jan  1 00:00:00 1970
From: Roland Dreier <rdreier@cisco.com>
Subject: Re: Question regarding SLAB corruption
Date: Mon, 09 Jul 2007 12:25:16 -0700
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	09 Jul 2007 19:29:59 +0100")
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To: Keir Fraser <keir@xensource.com>
Cc: Lukas Hejtmanek <xhejtman@ics.muni.cz>, xen-devel@lists.xensource.com
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 > Oh! I take it then that the infiniband driver will call sync_single() on
 > subsections of a mapped region? I haven't seen that behaviour before and it
 > will kill lib/swiotlb.c (the generic Linux swiotlb implementation) just as
 > surely as it does the Xen-specific swiotlb!

I guess it is not being hit on non-Xen Linux because mthca sets a
64-bit DMA mask and hence bypasses swiotlb.

However what you point out does seem to be a bug:
Documentation/DMA-API.txt says:

    void
    dma_sync_single(struct device *dev, dma_addr_t dma_handle, size_t size,
                    enum dma_data_direction direction)

    ...

    synchronise a single contiguous or scatter/gather mapping.  All the
    parameters must be the same as those passed into the single mapping
    API.

so it seems not really kosher to do on a subsection of a mapping...

I'll take a look at how we can do better here.

 - R.