linux-kernel - Re: [PATCH 12/12] crypto: caam - change JR device ownership scheme

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Date:   Thu, 19 Sep 2019 11:19:22 +0000
From:   Horia Geanta <horia.geanta@....com>
To:     Andrey Smirnov <andrew.smirnov@...il.com>,
        Leonard Crestez <leonard.crestez@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>
CC:     "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        Chris Healy <cphealy@...il.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Iuliana Prodan <iuliana.prodan@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Abel Vesa <abel.vesa@....com>
Subject: Re: [PATCH 12/12] crypto: caam - change JR device ownership scheme

On 9/18/2019 6:13 AM, Andrey Smirnov wrote:
>> I think you need to do some form of slow wait loop in jrpriv until
>> jrpriv->tfm_count reaches zero.
> Hmm, what do we do if it never does? Why do you think it would be
> better than cancelling all outstanding jobs and resetting the HW?
> 
Herbert,

What should a driver do when:
-user tries to unbind it AND
-there are tfms referencing algorithms registered by this driver

1. If driver tries to unregister the algorithms during its .remove()
callback, then this BUG_ON is hit:

int crypto_unregister_alg(struct crypto_alg *alg)
{
[...]
        BUG_ON(refcount_read(&alg->cra_refcnt) != 1);

2. If driver exits without unregistering the algorithms,
next time one of the tfms referencing those algorithms will be used
bad things will happen.

3. There is no mechanism in crypto core for notifying users
to stop using a tfm.

Thanks,
Horia