Messages in this thread | | | Date | Wed, 23 Jan 2008 15:12:36 +0100 | From | Gerd Hoffmann <> | Subject | Re: [kvm-devel] [PATCH] export notifier #1 |
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Hi,
>> That would render the notifies useless for Xen too. Xen needs to >> intercept the actual pte clear and instead of just zapping it use the >> hypercall to do the unmap and release the grant. > > We are tackling that by having our own page table hanging off the > structure representing our seg (thing created when we do the equiv of > your grant call).
--verbose please. I don't understand that "own page table" trick. Is that page table actually used by the processor or is it just used to maintain some sort of page list?
>> Current implementation uses a new vm_ops operation which is called if >> present instead of doing a ptep_get_and_clear_full(). It is in the >> XenSource tree only, mainline hasn't this yet due to implementing only >> the DomU bits so far. When adding Dom0 support to mainline we'll need >> some way to handle it, and I'd like to see the notifies be designed in a >> way that Xen can simply use them. > > Would the callouts Christoph proposed work for you if you maintained > your own page table and moved them after the callouts the mmu_notifiers > are using.
I *think* it would. I'm not that deep in the VM details to be sure though. One possible problem I see is that the hypercall does also tear down the mapping, so this isn't just a notify but also changes the page tables, which could confuse the VM later on when it comes to the actual pte clearing.
cheers, Gerd
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