[ofa-general] Re: [PATCH 01 of 11] mmu-notifier-core

[Andrea Arcangeli]

On Sun, May 04, 2008 at 02:13:45PM -0500, Robin Holt wrote:
> > diff --git a/mm/Kconfig b/mm/Kconfig
> > --- a/mm/Kconfig
> > +++ b/mm/Kconfig
> > @@ -205,3 +205,6 @@ config VIRT_TO_BUS
> >  config VIRT_TO_BUS
> >  	def_bool y
> >  	depends on !ARCH_NO_VIRT_TO_BUS
> > +
> > +config MMU_NOTIFIER
> > +	bool
> 
> Without some text following the bool keyword, I am not even asked for
> this config setting on my ia64 build.

Yes, this was explicitly asked by Andrew after his review. This is the
explanation pasted from the changelog.

3) It'd be a waste to add branches in the VM if nobody could possibly
   run KVM/GRU/XPMEM on the kernel, so mmu notifiers will only enabled
   if CONFIG_KVM=m/y. In the current kernel kvm won't yet take
   advantage of mmu notifiers, but this already allows to compile a
   KVM external module against a kernel with mmu notifiers enabled and
   from the next pull from kvm.git we'll start using them. And
   GRU/XPMEM will also be able to continue the development by enabling
   KVM=m in their config, until they submit all GRU/XPMEM GPLv2 code
   to the mainline kernel. Then they can also enable MMU_NOTIFIERS in
   the same way KVM does it (even if KVM=n). This guarantees nobody
   selects MMU_NOTIFIER=y if KVM and GRU and XPMEM are all =n.