[openib-general] [ANNOUNCE] GSI Implementation Candidate

[Dror Goldenberg]

> -----Original Message-----
> From: Roland Dreier [mailto:roland at topspin.com]
> Sent: Monday, August 02, 2004 8:39 PM
> 
> 
>     Grant> I don't understand how protection domains play with DMA. I
>     Grant> gather so far the HCA hosts a virtual -> DMA mapping table
>     Grant> which the HCA driver keeps up to date. Is the protection
>     Grant> domain used by the HCA to limit which entries in the table
>     Grant> a process on a remote host may derefence?
> 
> Every queue pair and every memory region is created in some protection
> domain.  For a memory region to be used by an operation on a queue
> pair, their protection domains must match.  However, the verbs
> extensions define a "default L_Key" (for kernel use only) that turns
> off both virtual->physical translation and protection domain
> checking.  It's almost possible to simulate this on the current
> Mellanox HCA, except that I don't know of a way to turn off protection
> domain checking, so we'll have to create one pseudo-default L_Key per
> protection domain.
> 
>  - Roland
> 

It is not possible to turn off PD check on a MR in Tavor. You will have 
to create an MR for each PD that you need. One way to go is to map
all kernel apps to the same PD, but you probably don't want to do such
a thing.
Once we get to verbs extensions, you can configure Arbel to disable 
the PD check for certain QPs.

-Dror
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