linux-kernel - Re: [PATCH V6 5/7] crypto: AES CBC multi-buffer glue code

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Date:   Tue, 18 Jul 2017 18:18:59 -0700
From:   Megha Dey <megha.dey@...el.com>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>, davem@...emloft.net,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V6 5/7] crypto: AES CBC multi-buffer glue code

On Tue, 2017-07-18 at 17:52 -0700, Tim Chen wrote:
> On 07/17/2017 10:41 PM, Herbert Xu wrote:
> > On Tue, Jun 27, 2017 at 05:26:13PM -0700, Megha Dey wrote:
> >>
> >> +static void completion_callback(struct mcryptd_skcipher_request_ctx *rctx,
> >> +			    struct mcryptd_alg_cstate *cstate,
> >> +			    int err)
> >> +{
> >> +	struct skcipher_request *req = cast_mcryptd_ctx_to_req(rctx);
> >> +
> >> +       /* remove from work list and invoke completion callback */
> >> +	spin_lock(&cstate->work_lock);
> >> +	list_del(&rctx->waiter);
> >> +	spin_unlock(&cstate->work_lock);
> >> +
> >> +	if (irqs_disabled())
> >> +		rctx->complete(&req->base, err);
> >> +	else {
> >> +		local_bh_disable();
> >> +		rctx->complete(&req->base, err);
> >> +		local_bh_enable();
> >> +	}
> >> +}
> > 
> > The fact that you need to do this check means that this design is
> > wrong.  You should always know what context you are in.
> > 
> 
> I think you are right.  The irqs_disabled check is not necessary
> as we only call this function in the context of the mcryptd thread.
> When I wrote the original mb algorithms I was probably unsure
> and put this check in as a precaution in other mb algorithms and
> Megha did the same.

I will make this change.
> 
> >> +/*
> >> + * CRYPTO_ALG_ASYNC flag is passed to indicate we have an ablk
> >> + * scatter-gather walk.
> >> + */
> >> +static struct skcipher_alg aes_cbc_mb_alg = {
> >> +	.base = {
> >> +		.cra_name		= "cbc(aes)",
> >> +		.cra_driver_name	= "cbc-aes-aesni-mb",
> >> +		.cra_priority		= 500,
> >> +		.cra_flags		= CRYPTO_ALG_INTERNAL,
> >> +		.cra_blocksize		= AES_BLOCK_SIZE,
> >> +		.cra_ctxsize		= CRYPTO_AES_CTX_SIZE,
> >> +		.cra_module		= THIS_MODULE,
> >> +	},
> >> +	.min_keysize	= AES_MIN_KEY_SIZE,
> >> +	.max_keysize	= AES_MAX_KEY_SIZE,
> >> +	.ivsize		= AES_BLOCK_SIZE,
> >> +	.setkey		= aes_set_key,
> >> +	.encrypt	= mb_aes_cbc_encrypt,
> >> +	.decrypt	= mb_aes_cbc_decrypt
> >> +};
> > 
> > So this claims to be a sync algorithm.  Is this really the case?

yes, the inner algorithm is sync whereas the outer algorithm is async.
> > 
> > Cheers,
> > 
>