Re: [kvm-devel] [patch 2/4] mmu_notifier: Callbacks to invalidate address ranges

[Robin H. <ho...@sg...>]

On Fri, Feb 01, 2008 at 03:19:32PM -0800, Christoph Lameter wrote:
> On Fri, 1 Feb 2008, Robin Holt wrote:
> 
> > We are getting this callout when we transition the pte from a read-only
> > to read-write.  Jack and I can not see a reason we would need that
> > callout.  It is causing problems for xpmem in that a write fault goes
> > to get_user_pages which gets back to do_wp_page that does the callout.
> 
> Right. You placed it there in the first place. So we can drop the code 
> from do_wp_page?

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.

Thanks,
Robin