Re: [PATCH v2 4/4] crypto: qat - fallback for xts with 192 bit keys

[Giovanni Cabiddu <giovanni.cabiddu@intel.com>]

Thanks for your feedback Ard.

On Fri, Jun 26, 2020 at 08:15:16PM +0200, Ard Biesheuvel wrote:
> On Fri, 26 Jun 2020 at 10:04, Giovanni Cabiddu
> <giovanni.cabiddu@intel.com> wrote:
> >
> > +static int qat_alg_skcipher_init_xts_tfm(struct crypto_skcipher *tfm)
> > +{
> > +       struct qat_alg_skcipher_ctx *ctx = crypto_skcipher_ctx(tfm);
> > +       int reqsize;
> > +
> > +       ctx->ftfm = crypto_alloc_skcipher("xts(aes)", 0, CRYPTO_ALG_ASYNC);
> 
> Why are you only permitting synchronous fallbacks? If the logic above
> is sound, and copies the base.complete and base.data fields as well,
> the fallback can complete asynchronously without problems.
> Note that SIMD s/w implementations of XTS(AES) are asynchronous as
> well, as they use the crypto_simd helper which queues requests for
> asynchronous completion if the context from which the request was
> issued does not permit access to the SIMD register file (e.g., softirq
> context on some architectures, if the interrupted context is also
> using SIMD)
I did it this way since I though I didn't have a way to test it with an
asynchronous sw implementation.
I changed this line to avoid masking the asynchronous implementations
and test it by forcing simd.c to use always cryptd (don't know if there
is a simpler way to do it).

Also, I added to the mask CRYPTO_ALG_NEED_FALLBACK so I don't get another
implementation that requires a fallback.

I'm going to send a v3.

Regards,

-- 
Giovanni