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    SubjectRe: Nick's core remove PageReserved broke vmware...
    Quoting Hugh Dickins <hugh@veritas.com>:
    > > All existing drivers that set VM_DONTCOPY also set VM_IO.
    > > So lets just disable playing with these flags from madvise if VM_IO is set.
    > > There's no reason I can see that the driver should have a say
    > > on what the process does with its own (non-IO) memory.
    > > Sounds good?
    >
    > You're then saying that a process cannot set VM_DONTCOPY on a VM_IO
    > area to prevent the first child getting the area, but clear it after
    > so the next child does get a copy of the area. I think it'd be wrong
    > (surprising) to limit the functionality in that way.

    Okay, I guess. I am just trying to avoid more VM_ flags.
    Cant we get rid of the last requirement, then?
    I dont see why the driver should have a say on what the process does with its
    own memory.

    > > By the way, as a separate issue, we still have a problem with DMA to pages
    > > which are *needed* by the child process. What do you think about VM_COPY
    > > (to do the old unix thing of actually copying the page instead of
    > > setting the COW flag) and a matching madvise call to set/clear it?
    >
    > I don't much want to add another path into copy_pte_range, actually
    > copying pages. If the process really wants DMA into such areas,
    > then it should contain the code for the child to COW them itself?
    >
    > Hugh

    How do you do that, say, for a stack page, or global data section?

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