Re: [PATCH 5.15 000/476] 5.15.149-rc1 review

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Apr 25, 2024 at 03:46:18PM -0700, Guenter Roeck wrote:
> Hi,
> 
> On 2/21/24 05:00, Greg Kroah-Hartman wrote:
> > This is the start of the stable review cycle for the 5.15.149 release.
> > There are 476 patches in this series, all will be posted as a response
> > to this one.  If anyone has any issues with these being applied, please
> > let me know.
> > 
> > Responses should be made by Fri, 23 Feb 2024 12:59:02 +0000.
> > Anything received after that time might be too late.
> > 
> [ ... ]
> 
> > Herbert Xu <herbert@gondor.apana.org.au>
> >      crypto: api - Disallow identical driver names
> > 
> 
> This patch results in a severe performance regression on arm64 systems;
> there is more than 50% throughput loss on some sequential read tests.
> The problem affects v5.15.y and older kernel branches.
> 
> Analysis shows that v5.15.y and older kernel _do_ try to register the same
> crypto algorithm twice, once through
> 
>  __crypto_register_alg
>  crypto_register_alg
>  crypto_register_skciphers
>  aes_init
> 
> and then again through
> 
>  __crypto_register_alg
>  crypto_register_alg
>  crypto_register_skcipher
>  simd_skcipher_create_compat
>  aes_init
> 
> After above patch was applied, the second registration fails, resulting
> in the regression.
> 
> The problem is not seen in later kernels due to commit 676e508122d9
> ("crypto: arm64/aes-ce - stop using SIMD helper for skciphers"). Applying this
> commit or reverting above commit fixes the regression in v5.15.y and older.
> 
> Thanks is due to Momoko Hattori for reporting the problem and finding the
> offending patch, Doug Anderson for finding the duplicate registration attempt,
> and Brian Norris for finding the fix. I copied them on this e-mail in case
> there are further questions.

Thanks for the report.  I got a report that this breaks some android
systems as well due to some FIPS crypto code that happens to duplicate
the names as well.  I think reverting it makes sense and I'll queue that
up for the next round of releases.

greg k-h