Re: [PATCH v2 04/13] RISC-V: crypto: add Zvkned accelerated AES implementation

[Eric Biggers]

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