[PATCH] powerpc/book3s64/kuap: SPRN_AMR modification need CSI instructions before and after
Nicholas Piggin
npiggin at gmail.com
Mon Apr 20 11:12:21 AEST 2020
Excerpts from Nicholas Piggin's message of April 20, 2020 10:17 am:
> Excerpts from Aneesh Kumar K.V's message of April 19, 2020 11:53 pm:
>> As per the ISA, context synchronizing instructions is needed before and after
>> SPRN_AMR update. Use isync before and the CSI after is implied by the rfid
>> that we will use to switch to a new context.
>
> Not entirely sure if we need this. This will restore AMR to more
> permissive, so if it executes ahead of a stray load from this
> context, it won't make it fault.
>
> That said, leaving this end open makes it harder to reason about
> user access protection I guess, so let's add it.
We probably should test whether it needs updating, like the entry
code does.
Thanks,
Nick
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