[ofa-general] [PATCH RFC] ib_mthca: avoid recycling FMR R_Keys too soon

[Olaf Kirch]

On Thursday 21 February 2008 12:42, Or Gerlitz wrote:
> As far as I understand under Sinai you must issue an adjust_key call 
> when the key is about to wraparound, correct?

I don't think so. On Arbel, ib_mthca uses the entire upper part of the
32bit word as the sequence counter. Is SINAI_OPT is set, the sequence
counter is in bits 25-31 (17-24 seem to be reserved, and bit 3 is
mirrored to bit 23 - this is what adjust_key seems to be doing).

If SINAI_OPT is not set, the sequence counter is in bits 17-31, and
adjust_key is a no-nop.

So when the sequence counter overflows, it doesn't spill into any
reserved bit.

At least that's how I read the code.

Olaf
-- 
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