Re: [PATCH] lib/crypto: riscv: Depend on RISCV_EFFICIENT_VECTOR_UNALIGNED_ACCESS

[Eric Biggers <ebiggers@kernel.org>]

On Thu, Feb 12, 2026 at 11:34:00AM +0100, Andreas Schwab wrote:
> On Dez 06 2025, Eric Biggers wrote:
> 
> > Replace the RISCV_ISA_V dependency of the RISC-V crypto code with
> > RISCV_EFFICIENT_VECTOR_UNALIGNED_ACCESS, which implies RISCV_ISA_V as
> > well as vector unaligned accesses being efficient.
> 
> That should be a runtime dependency.
> 

Currently there's no easy way to make it a runtime dependency,
especially given RISC-V's support for systems where the
"vector unaligned accesses are supported and efficient" property can
vary across CPUs on the same system and thus also vary at runtime as
CPUs go online and offline.  See
https://lore.kernel.org/linux-riscv/20251206195655.GA4665@quark/ where I
described these challenges in more detail.

I'd certainly *like* to make it a runtime dependency.  But the RISC-V
folks will need to provide a way to do that.  Part of that will likely
involve dropping support for systems where some CPUs don't have the same
feature set as the boot CPU, aligning with the other architectures.

For now, this patch was the only real option.

- Eric