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    SubjectRe: [PATCH] NOMMU: use copy_*_user_page() in access_process_vm()
    On 12/08/2009 10:19 PM, David Howells wrote:
    > Jie Zhang<jie.zhang@analog.com> wrote:
    >
    >> I agree on using 0 instead of NULL. But for !MMU, I think, vaddr is always as
    >> same as addr. So we don't need to pass it?
    >
    > FRV flushes the vaddr because in MMU mode the cache flush instructions take
    > virtual addresses, so if we pass addr as vaddr, I can use the same cache flush
    > code for both modes. I suspect it makes little difference to the amount of
    > code if we pass that rather than 0, as the value is already computed, and
    > either way, it's going to take one instruction to set up the argument.
    >
    > Note that Blackfin assumes that it may use the dst address for flushing - an
    > assumption that isn't valid in MMU mode with a VIVT cache (which I presume
    > Blackfin isn't, but other CPUs are).
    >
    Thanks for your explanation. Now I understand why passing add as vaddr
    is better.


    Jie


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