Subject: Re: cleanup the RAID5 XOR library v4

From: Eric Biggers <[email-masked]>
Date: Sun, 29 Mar 2026 21:07:24 -0700

On Sun, Mar 29, 2026 at 03:51:26PM -0700, Andrew Morton wrote:
> > 
> > Reviewed-by: Eric Biggers <[email-masked]>
> 
> Great, thanks, added to all changelogs.
> 
> > But yes, as Andrew mentioned there are two "xor: add a better public
> > API" patches.  They should be folded together.
> 
> I folded them.
> 
> I'm a bit wobbly about upstreaming all this for 7.1-rc1.  It hits on a
> lot of stuff and I don't think we've heard a lot from the affected
> maintainers.
> 
> otoh, we're unlikely to learn much from an additional nine weeks in
> linux-next so at some point one has to forge ahead and rely on seven
> weeks of -rc to address any remaining niggles.  And I'm confident that
> Christoph will support his work well.
> 
> But still, hearing some reassuring words about this would be
> appreciated ;)

The architecture-optimized crypto and CRC code has been the same way.
I've been working on it across architectures, and most of the arch
maintainers don't pay much attention to it.

I've seen engagement from a few of them, for example s390.  But as a
general rule it's a separate group of people working on this code.

I think seeing the same for lib/raid/ is expected.  So while the arch
maintainers are always welcome to chime in, I don't think we need to
wait for all of them, as then we'd be waiting forever.

Re testing, I've been running the crypto, CRC, and now the XOR KUnit
tests in QEMU for 8 architectures (arm, arm64, mips, powerpc, riscv,
s390, sparc, and x86), and over 40 variants within those (e.g. varying
CONFIG_64BIT, CONFIG_CPU_BIG_ENDIAN, and QEMU's "-cpu" flag).  They are
all passing, including the XOR test that Christoph added in this series.

(So I guess feel free to add:

    Tested-by: Eric Biggers <[email-masked]>

to all the patches in this series as well.)

That still doesn't cover all the arch-optimized code, due to me missing
various combinations or QEMU not supporting them.  But it's something.

I'm also hoping that with the move to standard KUnit tests, we'll get a
larger group of people, including projects like KernelCI, that simply
run *all* the kernel's KUnit tests on whatever platforms they care
about.  That approach is more scalable.

- Eric