Re: [PATCH 10/11] target/arm: Make SPSR_hyp accessible for Cortex-R52

[Peter Maydell]

On Thu, 14 Jul 2022 at 16:46, Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Thu, 14 Jul 2022 at 15:54, Tobias Roehmel <quic_trohmel@quicinc.com> wrote:
> >
> > From: Tobias Röhmel <quic_trohmel@quicinc.com>
> >
> > The Cortex-R52 can access SPSR_hyp from hypervisor mode
> > as discussed here: https://github.com/zephyrproject-rtos/zephyr/issues/47330
>
> The v8R Supplement pseudocode aarch32/functions/system/SPSRaccessValid
> says this is UNPREDICTABLE:
>
> when '11110' // SPSR_hyp
>     if !HaveEL(EL2) || mode != M32_Monitor then UNPREDICTABLE;
>
> so unless that's incorrect then I think QEMU is within its rights
> to UNDEF this (and real hardware may choose to UNDEF or not).
>
> I will enquire about whether there is a bug in the sample R52
> startup code.

The author of the startup code example agrees it's a bug that went
unnoticed because the FVP happens to permit this UNPREDICTABLE case,
so we don't need this QEMU patch.

-- PMM