Re: [PATCH v4 20/45] target/arm: Handle cpreg registration for missing EL

[Peter Maydell]

On Tue, 3 May 2022 at 17:45, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 5/3/22 09:34, Peter Maydell wrote:
> > "set CONST on the cpreg" is what the code does, but it's not
> > what the architecture wants. In particular, if the EL2 cpreg defines
> > a non-zero resetvalue then the EL3-no-EL2 CPU will get a
> > "reads as constant that value" rather than "reads as zero".
> > CNTHCTL_EL2 and MDCR_EL2 are examples of this.
>
> Ah, I'd missed those.  I guess I need a third bit to indicate keeping the 
> resetvalue, for
> e.g. VPIDR_EL2, which is why the code is written the way it is.

Or you could just treat VPIDR_EL2 as a special case and keep
the cpreginfo we have for it for the el3-no-el2 case.

thanks
-- PMM