[PATCH v2 0/2] ARM/arm64: errata: Remove AES hwcap for 32bit tasks on A57/A72

[James Morse]

Hello,

These patches remove the AES HWCAP on A57 and A72 for aarch32 user-space
processes due to erratum #1742098 and #1655431. An interrupt between two
instructions will cause these parts to get the wrong result.
These extensions are optional, so software should have a fallback
implementation.

The 32bit patch is new for v2, as Ard points out the behaviour should
be the same here.

Operating on the HWCAP bitmap directly avoids affecting KVM, which
was the problem with v1. But it does mean HWCAP_PMULL is still visible
to aarch32 processes. This isn't affected by the erratum, but is detected
from the same field in the ID register. PMULL is value '2', AES is value '1'.
User-space would be crazy to let PMULL imply AES, right ...

There is no dependency between the two patches.

[v1] https://lore.kernel.org/linux-arm-kernel/20220127122914.1585008-1-james.morse@arm.com/
[A57] https://developer.arm.com/documentation/epm049219/2300  #1742098
[A72 https://developer.arm.com/documentation/epm012079/11     #1655431


Thanks,

James Morse (2):
  arm64: errata: Remove AES hwcap for COMPAT tasks
  ARM: Remove AES hwcap for parts affected by errata

 Documentation/arm64/silicon-errata.rst |  4 ++++
 arch/arm/kernel/setup.c                |  9 +++++++++
 arch/arm64/Kconfig                     | 16 ++++++++++++++++
 arch/arm64/kernel/cpu_errata.c         | 16 ++++++++++++++++
 arch/arm64/kernel/cpufeature.c         | 11 ++++++++++-
 arch/arm64/tools/cpucaps               |  1 +
 6 files changed, 56 insertions(+), 1 deletion(-)

-- 
2.30.2