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

[Arnd Bergmann]

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.

        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/