Re: [PATCH] powerpc/crypto/chacha-p10: Fix failure on non Power10

[Herbert Xu <herbert@gondor.apana.org.au>]

On Fri, Mar 29, 2024 at 12:02:00AM +1100, Michael Ellerman wrote:
> The chacha-p10-crypto module provides optimised chacha routines for
> Power10. It also selects CRYPTO_ARCH_HAVE_LIB_CHACHA which says it
> provides chacha_crypt_arch() to generic code.
> 
> Notably the module needs to provide chacha_crypt_arch() regardless of
> whether it is loaded on Power10 or an older CPU.
> 
> The implementation of chacha_crypt_arch() already has a fallback to
> chacha_crypt_generic(), however the module as a whole fails to load on
> pre-Power10, because of the use of module_cpu_feature_match().
> 
> This breaks for example loading wireguard:
> 
>   jostaberry-1:~ # modprobe -v wireguard
>   insmod /lib/modules/6.8.0-lp155.8.g7e0e887-default/kernel/arch/powerpc/crypto/chacha-p10-crypto.ko.zst
>   modprobe: ERROR: could not insert 'wireguard': No such device
> 
> Fix it by removing module_cpu_feature_match(), and instead check the
> CPU feature manually. If the CPU feature is not found, the module
> still loads successfully, but doesn't register the Power10 specific
> algorithms. That allows chacha_crypt_generic() to remain available for
> use, fixing the problem.
> 
>   [root@fedora ~]# modprobe -v wireguard
>   insmod /lib/modules/6.8.0-00001-g786a790c4d79/kernel/net/ipv4/udp_tunnel.ko
>   insmod /lib/modules/6.8.0-00001-g786a790c4d79/kernel/net/ipv6/ip6_udp_tunnel.ko
>   insmod /lib/modules/6.8.0-00001-g786a790c4d79/kernel/lib/crypto/libchacha.ko
>   insmod /lib/modules/6.8.0-00001-g786a790c4d79/kernel/arch/powerpc/crypto/chacha-p10-crypto.ko
>   insmod /lib/modules/6.8.0-00001-g786a790c4d79/kernel/lib/crypto/libchacha20poly1305.ko
>   insmod /lib/modules/6.8.0-00001-g786a790c4d79/kernel/drivers/net/wireguard/wireguard.ko
>   [   18.910452][  T721] wireguard: allowedips self-tests: pass
>   [   18.914999][  T721] wireguard: nonce counter self-tests: pass
>   [   19.029066][  T721] wireguard: ratelimiter self-tests: pass
>   [   19.029257][  T721] wireguard: WireGuard 1.0.0 loaded. See www.wireguard.com for information.
>   [   19.029361][  T721] wireguard: Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
> 
> Reported-by: Michal Suchánek <msuchanek@suse.de>
> Closes: https://lore.kernel.org/all/20240315122005.GG20665@kitsune.suse.cz/
> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
> ---
>  arch/powerpc/crypto/chacha-p10-glue.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)

Acked-by: Herbert Xu <herbert@gondor.apana.org.au>

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt