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    SubjectRe: alpha iommu fixes
    On Mon, May 21, 2001 at 12:05:20AM +1000, Andrew Morton wrote:
    > Andrea Arcangeli wrote:
    > >
    > > [ cc'ed to l-k ]
    > >
    > > > DMA-mapping.txt assumes that it cannot fail.
    > >
    > > DMA-mapping.txt is wrong. Both pci_map_sg and pci_map_single failed if
    > > they returned zero. You either have to drop the skb or to try again later
    > > if they returns zero.
    > >
    > Well this is news to me. No drivers understand this.

    Yes, almost all drivers are buggy.

    > How long has this been the case? What platforms?

    Always and all platforms.

    Just think about this, you have 2^32 of bus address space, and you
    theoritically can start I/O for more than 2^32 of phys memory, see?
    Whatever platform it is it will never be able to guarantee all mappings
    to succeed.

    > For netdevices at least, the pci_map_single() call is always close
    > to the site of the skb allocation. So what we can do is to roll
    > them together and use the existing oom-handling associated with alloc_skb(),
    > assuming the driver has it...


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