[openib-general] Re: [kDAPL]questions about the LMR creation of different types of memory

[Ian Jiang]

Hi Grant,
Thanks very much.
I scanned the IO-mapping.txt, DMA-API.txt and DMA-mapping.txt as soon as I
could and have got a main concept now.
As your mentioned, ULPs in OpenIB (e.g. SDP or IPoIB) are responsible for
properly mapping and unmapping for DMA use. AFAIK, SDP is implemented with
the IB native verbs. What about the kDAPL? In my opinion the kDAPL does not
do the mapping and unmapping work. So it is the responsibility of the kernel
applications using the kDAPL. Am I right?

On 12/17/05, Grant Grundler <iod00d at hp.com> wrote:
>
> While IO-mapping.txt gives a nice introduction into the topic
> of "bus addresses", the answer to the question lies in
> Documentation/DMA-API.txt. IO devices can only use "bus addresses"
> that are handed back by the interfaces described in DMA-API.txt.
> For OpenIB, ULPs (e.g. SDP or IPoIB) are responsible for properly
> mapping and unmapping for DMA use.
>
> While many architectures don't use IOMMU (and thus have 1:1
> between host physical:bus address), virtualization seems to be
> forcing the issue in the "near" future. All DMA access will need
> to be enforced to isolate virtualized guests. This is something
> some platforms with IOMMUs enforce today (e.g. Sparc64, PPC64 and
> PA-RISC).
>
> hth,
> grant
>



--
Ian Jiang
ianjiang.ict at gmail.com

Laboratory of Spatial Information Technology
Division of System Architecture
Institute of Computing Technology
Chinese Academy of Sciences
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