[PATCH 0/1] armv8: reduce core errata dispatch work

[Krzysztof Kozlowski]

On 24/05/2026 14:38, Josh Law wrote:
> Hey folks,
> 
> apply_core_errata() runs during early ARMv8 CPU entry, before
> lowlevel_init(). Today it still checks the Cortex-A53 and Cortex-A57
> paths even when the build has no matching core erratum enabled.
> 
> This patch leaves that dispatch code out unless one of the supported
> errata is enabled. For the A57 errata case, it reads MIDR_EL1 once and
> reuses the extracted CPU part number.
> 
> The erratum register writes stay behind the same CPU checks as before.
> For qemu_arm64_defconfig, where none of these errata are enabled,
> apply_core_errata() goes from 15 dispatch instructions to a single ret.
> For ls2080aqds_qspi_defconfig, which keeps the A57 path, the dispatch
> side goes from 33 instructions to 26. A KVM microbench of the same
> dispatch sequences showed 1.30x for the no errata case and 1.09x for
> the A57 miss case.
> 
> Josh Law (1):
>   armv8: reduce core errata dispatch work

That's another identity from Josh Law, since all previous got NAKed, and
100% AI generated code without review and without tests (I don't believe
what was claimed above).

I recommend ignoring and here is some background:

https://lore.kernel.org/all/cbd0aafa-bd45-4f4d-a2dd-440473657dba@lucifer.local/

Best regards,
Krzysztof