linux-kernel - Re: [PATCH v4 1/2] crypto: engine

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Date:   Thu, 12 Mar 2020 12:52:05 +0000
From:   Iuliana Prodan <iuliana.prodan@....com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
CC:     Baolin Wang <baolin.wang@...aro.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Corentin Labbe <clabbe.montjoie@...il.com>,
        Horia Geanta <horia.geanta@....com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Maxime Ripard <mripard@...nel.org>,
        Aymen Sghaier <aymen.sghaier@....com>,
        "David S. Miller" <davem@...emloft.net>,
        Silvano Di Ninno <silvano.dininno@....com>,
        Franck Lenormand <franck.lenormand@....com>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH v4 1/2] crypto: engine - support for parallel requests

On 3/12/2020 2:45 PM, Iuliana Prodan wrote:
> On 3/12/2020 5:26 AM, Herbert Xu wrote:
>> On Mon, Mar 09, 2020 at 12:51:32AM +0200, Iuliana Prodan wrote:
>>>
>>>    	ret = enginectx->op.do_one_request(engine, async_req);
>>> -	if (ret) {
>>> -		dev_err(engine->dev, "Failed to do one request from queue: %d\n", ret);
>>> -		goto req_err;
>>> +	can_enq_more = ret;
>>> +	if (can_enq_more < 0) {
>>> +		dev_err(engine->dev, "Failed to do one request from queue: %d\n",
>>> +			ret);
>>> +		goto req_err_1;
>>> +	}
>>
>> So this now includes the case of the hardware queue being full
>> and the request needs to be queued until space opens up again.
>> In this case, we should not do dev_err.  So you need to be able
>> to distinguish between the hardware queue being full vs. a real
>> fatal error on the request (e.g., out-of-memory or some hardware
>> failure).
>>
> There are two aspects here:
> - if all requests go through crypto-engine, and, in this case, if there
> is no space in hw queue, do_one_req returns 0, and actually there will
> be no case of do_one_request() < 0;
> - if there are other requests (non crypto API) that go to hw for
> execution (in CAAM we have split key or RNG) those might occupy the hw
> queue, after crypto-engine returns that it still has space. This case
> wasn't supported before my modifications and neither with these patches.
> This use-case can be solved by retrying to send the request to hw -
> enqueue it back to crypto-engine, in the head of the queue (to keep the
> order, and send it again to hw).
> I've tried this, but it implies modifications in all drivers. For
> example, a driver, in case of error, it frees the resources of the
> request. So, will need to map again a request.
> 

I believe this recovery mechanism should be handled in other patch (series).
Herbert, what is your proposal to move forward?

Thanks,
Iulia