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

Andrea Arcangeli
2008-05-04T22:08:25Z

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.

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