[ofa-general] Oops in mthca

[Pradeep Satyanarayana]

I was out on vacation the last week of December and hence the delayed response.

Roland Dreier wrote:
>  > I discovered the following Oops while developing a patch to enable SRQ on HCAs with fewer than
>  > 16 SG elements.
> 
> So is this oops with some version of your patch for limited SRQ
> scatter entries applied?  It's hard to know exactly what is going
> wrong but I suspect that if you get a device that allows more than 16
> SRQ scatter entries, your patch passes that value for num_sg without
> changing the declaration of rx_sge[] to have enough entries, so when
> posting the receive request, the low-level driver goes off the end of
> the array.
 
rx_sge[] could have been the culprit. I now limit the max_sge to IPOIB_CM_RX_SG, 
and so that is not an issue any more. 

The latest patch submitted :
http://lists.openfabrics.org/pipermail/general/2007-December/044298.html

has this fix.

> 
>  > The root of this issue appears to be that ib_query_device(priv->ca, &attr)
>  > reports an incorrect value for attr.max_srq_sge. The value that
>  > ib_query_device returns is 28 (instead of 16 that I expected).
> 
> Why do you think the value 28 is incorrect?  

At one stage ib_query_device() was returning max_srq_sge of 28 and
ib_query_srq() returned max_sge of 16. And because of the discrepancy
I thought 28 was incorrect.

However, now both return 28 and that is probably a moot point.

Pradeep