Re: stable request

Thomas Backlund
2021-03-16T12:16:42Z

Den 16.3.2021 kl. 12:17, skrev Ard Biesheuvel:
> On Tue, 16 Mar 2021 at 10:21, Thomas Backlund <tmb@tmb.nu> wrote:
>> Den 16.3.2021 kl. 08:37, skrev Ard Biesheuvel:
>>> Please consider backporting commit
>>>
>>> 86ad60a65f29dd862a11c22bb4b5be28d6c5cef1
>>> crypto: x86/aes-ni-xts - use direct calls to and 4-way stride
>>>
>>> to stable. It addresses a rather substantial retpoline-related
>>> performance regression in the AES-NI XTS code, which is a widely used
>>> disk encryption algorithm on x86.
>>>
>> To get all the nice bits, we added the following in Mageia 5.10 / 5.11
>> series kerenels (the 2 first is needed to get the third to apply/build
>> nicely):
>>
> I will leave it up to the -stable maintainers to decide, but I will
> point out that none of the additional patches fix any bugs, so this
> may violate the stable kernel rules. In fact, I deliberately split the
> XTS changes into two patches so that the first one could be
> backported individually.

Yes, I understand that.

but commit

86ad60a65f29dd862a11c22bb4b5be28d6c5cef1
crypto: x86/aes-ni-xts - use direct calls to and 4-way stride

only applies cleanly on 5.11.

So if it's wanted in 5.10 you need the 2 others too... unless you intend to provide a tested backport...
and IIRC GregKH prefers 1:1 matching of patches between -stable and linus tree unless they are too intrusive.

As for the last one I seem to remember comments that it too was part of the "affects performance", but I might be remembering wrong... and since you are Author of them I assume you know better about the facts :)

That's why I listed them as an extra "hopefully helfpful" info and datapoint that they work...
We have been carrying them in 5.10 series since we rebased to 5.10.8 on January 17th, 2021

but in the end it's up to the -stable maintainers as you point out...

--
Thomas

> --
> Ard.
>
>
>> applied in this order:
>>
>> From 032d049ea0f45b45c21f3f02b542aa18bc6b6428 Mon Sep 17 00:00:00 2001
>> From: Uros Bizjak <ubizjak@gmail.com>
>> Date: Fri, 27 Nov 2020 10:44:52 +0100
>> Subject: [PATCH] crypto: aesni - Use TEST %reg,%reg instead of CMP $0,%reg
>>
>> From ddf169a98f01d6fd46295ec0dd4c1d6385be65d4 Mon Sep 17 00:00:00 2001
>> From: Ard Biesheuvel <ardb@kernel.org>
>> Date: Tue, 8 Dec 2020 00:34:02 +0100
>> Subject: [PATCH] crypto: aesni - implement support for cts(cbc(aes))
>>
>> From 86ad60a65f29dd862a11c22bb4b5be28d6c5cef1 Mon Sep 17 00:00:00 2001
>> From: Ard Biesheuvel <ardb@kernel.org>
>> Date: Thu, 31 Dec 2020 17:41:54 +0100
>> Subject: [PATCH] crypto: x86/aes-ni-xts - use direct calls to and 4-way
>> stride
>>
>> From 2481104fe98d5b016fdd95d649b1235f21e491ba Mon Sep 17 00:00:00 2001
>> From: Ard Biesheuvel <ardb@kernel.org>
>> Date: Thu, 31 Dec 2020 17:41:55 +0100
>> Subject: [PATCH] crypto: x86/aes-ni-xts - rewrite and drop indirections
>> via glue helper
>>
>> --
>> Thomas
>>