Re: [PATCH 1/2] crypto: pcrypt - Remove pcrypt

[Eric Biggers <ebiggers@kernel.org>]

On Fri, Jul 24, 2026 at 08:19:02PM +0200, Hendrik Donner wrote:
> 
> so i'm now on 7.1.4 with
> 
>   PCI: imx6: Keep i.MX6 Root Port MSI/MSI-X Capabilities with iMSI-RX to
> work around hardware bug
> 
> on top to be able to tune queue settings. And to have a working ethernet
> in the first place, without the patch the NETDEV WATCHDOG resets the
> card all the time due to queues stalling. But now more than 1 CPU are
> serving IRQs.
> 
> With pcrypt
> (seqiv(rfc4106(pcrypt(gcm_base(ctr-aes-neonbs,ghash-lib))))):
> 
> Upload:
> [  4]   0.00-60.00  sec   901 MBytes   126 Mbits/sec
> 
> Download:
> [  4]   0.00-60.00  sec  1.23 GBytes   177 Mbits/sec
> 
> Without pcrypt
> (seqiv(rfc4106(gcm_base(ctr-aes-neonbs,ghash-lib)))):
> 
> Upload:
> [  4]   0.00-60.00  sec   679 MBytes  94.9 Mbits/sec
> 
> Download:
> [  4]   0.00-60.00  sec   674 MBytes  94.3 Mbits/sec
> 
> So counterintuitively pcrypt matters more again. I repeated the tests a
> few times, those numbers are fairly representative. Every run is over a
> 60 sec window.

Thanks for trying it.  Perhaps this is related to the iperf3 test using
only a single flow?  Does that reflect the real-world case for you?

I'm also curious whether you're particularly attached to AES-GCM, or
whether you've considered switching to ChaCha20Poly1305 which would be
much faster on that CPU.  This could be done either by switching to
"rfc7539esp(chacha20,poly1305)" within IPsec, or by just switching to
WireGuard.

If none of those are options for you and you do want pcrypt to be kept
around, could you confirm that you're solely using 'crconf' (run as
root) to enable it, and in particular you're not relying on the
misfeature of also being able to enable it as an unprivileged user using
AF_ALG?  We can keep it around for a bit longer if really needed, but
the unprivileged stuff definitely has to go.  We should also keep in
mind that pcrypt does not get tested very well (as the crypto self-tests
just test serial use) and historically has had a lot of issues.

- Eric