[PATCH v4] arm64: errata: Work around AmpereOne's erratum AC04_CPU_23

[Catalin Marinas]

On Tue, May 13, 2025 at 11:45:14AM -0700, D Scott Phillips wrote:
> On AmpereOne AC04, updates to HCR_EL2 can rarely corrupt simultaneous
> translations for data addresses initiated by load/store instructions.
> Only instruction initiated translations are vulnerable, not translations
> from prefetches for example. A DSB before the store to HCR_EL2 is
> sufficient to prevent older instructions from hitting the window for
> corruption, and an ISB after is sufficient to prevent younger
> instructions from hitting the window for corruption.
> 
> Signed-off-by: D Scott Phillips <scott at os.amperecomputing.com>
> Reviewed-by: Oliver Upton <oliver.upton at linux.dev>

For the core arm64 bits:

Acked-by: Catalin Marinas <catalin.marinas at arm.com>

Marc, Will - any preference on how this should go in (kvm or arm64
trees)?