[PATCH] arm64: errata: Remove AES hwcap for COMPAT tasks on A57 and A72

[Robin Murphy]

On 2022-01-27 14:52, Arnd Bergmann wrote:
> On Thu, Jan 27, 2022 at 1:39 PM Ard Biesheuvel <ardb at kernel.org> wrote:
>> Cortex-A57 and Cortex-A72 have an erratum where an interrupt that
>> occurs between a pair of AES instructions in aarch32 mode may corrupt
>> the ELR. The task will subsequently produce the wrong AES result.
> 
>> Fortunately, the only A72 that is known to be widely deployed with
>> 32-bit kernels and/or user space is the Raspberry Pi 4, which does not
>> implement the crypto extensions.
> 
> I have previously used Amazon EC2 A1 instances (using Graviton 1, Cortex-A72)
> to run Debian armhf and armel user space in chroot environments. No idea how
> common that is for production environments, but there is a good chance that
> actual users might use e.g. 32-bit docker images for Alpine Linux on the same
> machines.
> 
> There are also some early A57/A72 chips used in Android devices that may
> frequently run 32-bit applications, or even be limited to 32-bit
> kernels, see [1].
> Not sure how likely it is for any of them to get (a backport of) this
> patch though.

Isn't ChromeOS still notoriously shipping AArch32 userspace? Between 
Mediatek and Rockchip, both A57 and A72 are definitely playing on that 
stage.

I'd concur that 32-bit *kernel* on v8 is a bit of a specialist sport, 
especially these days. IIRC Exynos 5433 might have been one of the more 
common Android setups for that, but 2015 is now an eternity ago in phone 
years...

Robin.

> 
>          Arnd
> 
> [1] https://www.androidpolice.com/2020/01/14/nvidias-shield-tv-dongle-can-only-run-32-bit-apps-but-you-probably-dont-need-to-panic/
> 
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