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Date:   Tue, 28 Nov 2023 12:12:28 -0800
From:   Eric Biggers <ebiggers@kernel.org>
To:     Conor Dooley <conor@kernel.org>
Cc:     Jerry Shih <jerry.shih@sifive.com>, paul.walmsley@sifive.com,
        palmer@dabbelt.com, aou@eecs.berkeley.edu,
        herbert@gondor.apana.org.au, davem@davemloft.net,
        conor.dooley@microchip.com, ardb@kernel.org, heiko@sntech.de,
        phoebe.chen@sifive.com, hongrong.hsu@sifive.com,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-crypto@vger.kernel.org
Subject: Re: [PATCH v2 04/13] RISC-V: crypto: add Zvkned accelerated AES
 implementation
Message-ID: <20231128201228.GE1148@sol.localdomain>
References: <20231127070703.1697-1-jerry.shih@sifive.com>
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 <20231128-await-tipper-2094715466f2@spud>
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On Tue, Nov 28, 2023 at 05:54:49PM +0000, Conor Dooley wrote:
> > +static inline bool check_aes_ext(void)
> > +{
> > +	return riscv_isa_extension_available(NULL, ZVKNED) &&
> > +	       riscv_vector_vlen() >= 128;
> > +}
> 
> I'm not keen on this construct, where you are checking vlen greater than
> 128 and the presence of Zvkned without checking for the presence of V
> itself. Can you use "has_vector()" in any places where you depend on the
> presence of vector please?

Shouldn't both of those things imply vector support already?

> Also, there are potentially a lot of places in this drivers where you
> can replace "riscv_isa_extension_available()" with
> "riscv_has_extension_likely()". The latter is optimised with
> alternatives, so in places that are going to be evaluated frequently it
> may be beneficial for you.

These extension checks are only executed in module_init functions, so they're
not performance critical.

- Eric