Messages in this thread | | | Date | Thu, 3 Nov 2005 17:14:21 +0200 | From | "Michael S. Tsirkin" <> | Subject | Re: Nick's core remove PageReserved broke vmware... |
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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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