Re: [patch 2/4] mmu_notifier: Callbacks to invalidate addressranges

[Andrea Arcangeli]

On Fri, Feb 01, 2008 at 05:35:28PM -0600, Robin Holt wrote:
> No, we need a callout when we are becoming more restrictive, but not
> when becoming more permissive.  I would have to guess that is the case
> for any of these callouts.  It is for both GRU and XPMEM.  I would
> expect the same is true for KVM, but would like a ruling from Andrea on
> that.

I still hope I don't need to take any lock in _range_start and that
losing coherency (w/o risking global memory corruption but only
risking temporary userland data corruption thanks to the page pin) is
ok for KVM.

If I would have to take a lock in _range_start like XPMEM is forced to
do (GRU is by far not forced to it, if it would switch to my #v5) then
it would be a problem.
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