Re: [PATCH v4 13/24] target/arm: Add ptw_idx to S1Translate

[Richard Henderson]

On 10/17/22 20:01, Peter Maydell wrote:
> On Tue, 11 Oct 2022 at 04:30, Richard Henderson
> <richard.henderson@linaro.org> wrote:
> > Hoist the computation of the mmu_idx for the ptw up to
> > get_phys_addr_with_struct and get_phys_addr_twostage.
> > This removes the duplicate check for stage2 disabled
> > from the middle of the walk, performing it only once.
> >
> > Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> > ---
> > +        if (!nstable) {
> > +            /* Stage2_S -> Stage2 or Phys_S -> Phys_NS */
> > +            ptw->in_ptw_idx &= ~1;
> > +            ptw->in_secure = false;
> > +        }
>
> I feel like this bitwise manipulation of the mmuidx values
> is leaving a landmine for any future re-organization of
> our mmuidx use. Can we do this just using the symbolic
> constant values?

I can't think of a way with just symbolic values,
but I can add BUILD_BUG_ON to validate expectations,
so that it's not a *hidden* landmine.  :-)


r~