[ofw] RE: Possible IPoIB DMA problems

[Fab Tillier]

>From: Tzachi Dar [mailto:tzachid at mellanox.co.il]
>Sent: Thursday, August 21, 2008 9:07 AM
>To: Anh Duong; ofw at lists.openfabrics.org
>Cc: Stan C. Smith; John Russo; Fab Tillier; Alex Estrin; Usha Srinivasan
>Subject: RE: Possible IPoIB DMA problems
>
>As far as I know all low-level drivers on open fabrics don't use DMA
>addresses. Leonid will be able to say more once he is back from
>vacation.

For SRP and 'normal' IPoIB packets the storport and NDIS drivers do the DMA mappings, respectively.  The solution for IPoIB's special packet handling is to allocate a common buffer for the receive buffers.  It should be pretty straight forward.

IBAL has the same problem internally with MAD buffers.  Allocating a common buffer for this is much more complicated due to how IBAL is designed (it doesn't know about device objects and Windows DMA).  A potential work around here would be to size the special QPs large enough that the MAD payload could be sent as an inline buffer.

-Fab