linux-kernel - Re: Clarification of allowed context for crypto routines

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Message-ID: <20090123223150.GA1264@gondor.apana.org.au>
Date:	Sat, 24 Jan 2009 09:31:50 +1100
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Andrey Borzenkov <arvidjaar@...l.ru>
Cc:	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Clarification of allowed context for crypto routines

Andrey Borzenkov <arvidjaar@...l.ru> wrote:
>
> As I can understand, user context requirement is due to potential for 
> setkey to sleep (although it appears, that currently the only module 
> that can sleep is shash which is calling kmalloc with GFP_KERNEL). Is it 
> correct?

Yep.

> But where is the difference between hard and softirq contexts? I fail to 
> see any technical reason for this requirement.

The reasons are two-fold:

1) Crypto operations are so slow in general that if you did them
in hard IRQ context it would just be wrong;

2) The highmem primitives we use are currently softirq only.  We
could make them work for hardirq as well, but because of 1) we
didn't.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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