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

Robin Holt
2008-05-05T02:26:09Z

On Mon, May 05, 2008 at 12:08:25AM +0200, Andrea Arcangeli wrote:
> 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.

Ah, so Andrew wants users of KVM to do a select of MMU_NOTIFIER. That
makes sense. I will change (fix) my Kconfig changes.

Thanks,
Robin