[openib-general] Question on get_dma_mr()
devesh28 at gmail.com
Tue Mar 28 22:03:13 PST 2006
Thanks to all of you
On 3/27/06, Roland Dreier <rdreier at cisco.com> wrote:
> Devesh> Hello all, Please any body explain me about the
> Devesh> functionality of verbs ib_get_dma_mr()?
> Actually, the responses you've gotten are not quite right.
> ib_get_dma_mr() returns a memory region that can be used for any _bus_
> addresses. In other words, if an S/G entry is passed to the driver
S/G entry ?
that uses the L_Key from ib_get_dma_mr() and an address of, say,
> 0xdeadbeef, then the RDMA device should use a bus address of
> 0xdeadbeef to access that memory.
What is the size of this region ? is there any limitation in providing this
The difference between bus addresses and physical addresses is
> significant when IOMMUs are present.
> This is somewhat similar to the verbs extensions notion of "reserved
> L_Key," except that it also provides an R_Key and the ability to
> specify the access permissions of the region.
Finally you mean to say in the implementation of this function providing
a unique L_Key and R_Key is sufficient. Is it?
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