Re: [PATCH v3] lib/crc: arm64: add NEON accelerated CRC64-NVMe implementation

[Eric Biggers <ebiggers@kernel.org>]

On Sun, Mar 29, 2026 at 07:43:38AM +0000, Demian Shulhan wrote:
> Implement an optimized CRC64 (NVMe) algorithm for ARM64 using NEON
> Polynomial Multiply Long (PMULL) instructions. The generic shift-and-XOR
> software implementation is slow, which creates a bottleneck in NVMe and
> other storage subsystems.
> 
> The acceleration is implemented using C intrinsics (<arm_neon.h>) rather
> than raw assembly for better readability and maintainability.
> 
> Key highlights of this implementation:
> - Uses 4KB chunking inside scoped_ksimd() to avoid preemption latency
>   spikes on large buffers.
> - Pre-calculates and loads fold constants via vld1q_u64() to minimize
>   register spilling.
> - Benchmarks show the break-even point against the generic implementation
>   is around 128 bytes. The PMULL path is enabled only for len >= 128.
> 
> Performance results (kunit crc_benchmark on Cortex-A72):
> - Generic (len=4096): ~268 MB/s
> - PMULL (len=4096): ~1556 MB/s (nearly 6x improvement)
> 
> Signed-off-by: Demian Shulhan <demyansh@gmail.com>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/log/?h=crc-next

Thanks!

- Eric