Re: [PATCH] target/arm: Allow only specific instructions based on the SCTLR_EL1.UCI bit

[Idan Horowitz]

On Thu, 20 Jan 2022 at 13:42, Peter Maydell <peter.maydell@linaro.org> wrote:
>
>
> But for all of these instructions the reginfo struct
> sets ".access = PL1_W". The .access field is always
> checked before the .accessfn, so for any of these instructions
> executed from EL0 I think we will always fail the .access
> check and UNDEF the insn without calling the .accessfn.
> So it doesn't matter that the .accessfn has "if EL0 then
> check SCTLR_EL1.UCI", because when running the accessfn
> for these insns we can never be in EL0.
>
> Am I missing something?
>

Hey, you are not missing anything, this patch indeed does not change
any external behaviour.
I should have specified, but the point of this patch is optimization:
during benchmarking of the various AArch64 instructions I found that
the cache flush instructions were quite slow, simply due to their
heavy access functions, so this is an attempt at simplifying them.

>
> thanks
> -- PMM

Regards,
Idan Horowitz