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> Date: Fri, 8 Feb 2008 16:16:34 -0800
> From: clameter@sgi.com
> To: rdreier@cisco.com
> CC: akpm@linux-foundation.org; andrea@qumranet.com; a.p.zijlstra@chello.nl; linux-mm@kvack.org; izike@qumranet.com; steiner@sgi.com; linux-kernel@vger.kernel.org; avi@qumranet.com; kvm-devel@lists.sourceforge.net; daniel.blueman@quadrics.com; holt@sgi.com; general@lists.openfabrics.org
> Subject: Re: [ofa-general] Re: [patch 0/6] MMU Notifiers V6
>
> On Fri, 8 Feb 2008, Roland Dreier wrote:
>
> > In general, this MMU notifier stuff will only be useful to a subset of
> > InfiniBand/RDMA hardware. Some adapters are smart enough to handle
> > changing the IO virtual -> bus/physical mapping on the fly, but some
> > aren't. For the dumb adapters, I think the current ib_umem_get() is
> > pretty close to as good as we can get: we have to keep the physical
> > pages pinned for as long as the adapter is allowed to DMA into the
> > memory region.
>
> I thought the adaptor can always remove the mapping by renegotiating
> with the remote side? Even if its dumb then a callback could notify the
> driver that it may be required to tear down the mapping. We then hold the
> pages until we get okay by the driver that the mapping has been removed.
>
> We could also let the unmapping fail if the driver indicates that the
> mapping must stay.
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