Re: [PATCH V3 6/6] crypto/nx: Add P9 NX support for 842 compression engine

[Haren Myneni <haren@linux.vnet.ibm.com>]

On 08/29/2017 02:23 PM, Benjamin Herrenschmidt wrote:
> On Tue, 2017-08-29 at 09:58 -0400, Dan Streetman wrote:
>>> +
>>> +       ret = -EINVAL;
>>> +       if (coproc && coproc->vas.rxwin) {
>>> +               wmem->txwin = nx842_alloc_txwin(coproc);
>>
>> this is wrong.  the workmem is scratch memory that's valid only for
>> the duration of a single operation.

Correct, workmem is used until crypto_free is called. 
>>
>> do you actually need a txwin per crypto transform?  or do you need a
>> txwin per coprocessor?  or txwin per processor?  either per-coproc or
>> per-cpu should be created at driver init and held separately
>> (globally) instead of a per-transform txwin.  I really don't see why
>> you would need a txwin per transform, because the coproc should not
>> care how many different transforms there are.
> 
> We should only need a single window for the whole kernel really, plus
> one per user process who wants direct access but that's not relevant
> here.

Opening send window for each crypto transform (crypto_alloc, compression/decompression, ..., crypto_free) so that does not have to wait for the previous copy/paste complete. VAS will map send and receive windows, and can cache in send windows (up to 128). So I thought using the same send window (per chip) for more requests (say 1000) may be adding overhead.

I will make changes if you prefer using 1 send window per chip.  

> 
> Cheers,
> Ben.
>