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

[Eric Biggers]

On Sun, Oct 11, 2026 at 10:29:29PM +0800, Huacai Chen wrote:
> +static inline u32 get_le32(const void *p)
> +{
> +	if (static_branch_likely(&have_ual))
> +		return *((__le32 *)p);
> +	else
> +		return get_unaligned_le32(p);
> +}

No, this is just broken.  The bare misaligned access is undefined
behavior in C.  Also, every other use of {get,put}_unaligned_* in the
kernel would need this; it is not specific to the CRC code.  Also, it is
inefficient to compile both code paths into the binary.

The only way that realistically works, as we know from the other
architectures, is for the unaligned access support to be known at
compile time, and to have {get,put}_unaligned_* do the right thing
accordingly.

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.

- Eric