Re: [PATCH 1/2] lib/crc: loongarch: Use hardware unaligned load in CRC32(C) loops

[Eric Biggers <ebiggers@kernel.org>]

On Mon, Oct 12, 2026 at 02:43:47PM +0800, Huacai Chen wrote:
> Yes, we considered modifying {get,put}_unaligned_* globally. But it is
> not arch-specific code and we have no way to override it.
> 
> On the other hand, the byte-to-byte {get,put}_unaligned_* is always
> correct, we are free to only optimise the hot path (like crc32 code).

The unaligned access macros are used in lots of other
performance-critical code.  Hacks in random places don't scale.

> > > Since loongarch made the incorrect decision to not specify unaligned
> > > access unconditionally, similar to RISC-V it can be worked around only
> > > by overriding that in the kconfig.  For loongarch that appears that
> > > already be implemented; just unset CONFIG_ARCH_STRICT_ALIGN when you
> > > know the kernel will run only on CPUs that have fixed this bug.
> > I think that we have the use cases to provide the general kernel instead of the two kernel with
> > different config, so the image increase will be tolerated.
> Yes, the default configuration is to keep CONFIG_ARCH_STRICT_ALIGN set
> for single kernel binary.

So don't do that.  It does not work for divergent unaligned access
support, as the other architectures have learned long ago.

- Eric