[PATCH 2/2] arm64: errata: Work around AmpereOne's erratum AC04_CPU_23

[D Scott Phillips]

Marc Zyngier <maz at kernel.org> writes:

> On Tue, 15 Apr 2025 23:13:43 +0100,
> D Scott Phillips <scott at os.amperecomputing.com> wrote:
>> 
>> Marc Zyngier <maz at kernel.org> writes:
>> 
>> > On Tue, 15 Apr 2025 16:47:11 +0100,
>> > If the write to HCR_EL2 can corrupt translations, what guarantees that
>> > such write placed on a page boundary (therefore requiring another TLB
>> > lookup to continue in sequence) will be able to get to the ISB?
>> 
>> Hi Marc, I understand now from the core team that an ISB on another page
>> will be ok as the problem is on the data side only.
>
> Are you guaranteed that a younger data access can't be hoisted up and
> affect things similarly? I don't see anything that would prevent this.

Yes that's my understanding, that the younger instructions
(mis-speculated or not) can't have their window for corruption of a
translation line up with the store to HCR due to the ISB.