Messages in this thread | | | Subject | Re: [ofa-general] Re: [patch 0/6] MMU Notifiers V6 | From | Roland Dreier <> | Date | Fri, 08 Feb 2008 16:12:42 -0800 |
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> We have done several rounds of discussion on linux-kernel about this so > far and the IB folks have not shown up to join in. I have tried to make > this as general as possible.
Sorry, this has been on my "things to look at" list for a while, but I haven't gotten a chance to really understand where things are yet.
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.
For the smart adapters, we just need a chance to change the adapter's page table when the kernel/CPU's mapping changes, and naively, this stuff looks like it would work.
Andrew, does that help?
- R.
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