Re: [PATCH 1/2] target/xtensa: wrap MMU and MPU state into structures

[Peter Maydell <peter.maydell@linaro.org>]

On Mon, 22 Jan 2024 at 18:45, Max Filippov <jcmvbkbc@gmail.com> wrote:
>
> On Mon, Jan 22, 2024 at 10:29 AM Peter Maydell <peter.maydell@linaro.org> wrote:
> >
> > On Fri, 19 Jan 2024 at 20:47, Max Filippov <jcmvbkbc@gmail.com> wrote:
> > > +    union {
> > > +        XtensaMMU mmu;
> > > +        XtensaMPU mpu;
> > > +    };
> >
> > Is it really worth having this be a union ? I suspect it will
> > make adding migration/savevm support later more awkward.
>
> I have a draft implementation of savevm for xtensa and I did this part
> using subsections with the .needed callback checking whether the
> MMU or MPU option is enabled in the config. I wonder where the
> awkwardness is expected.

Oh, well if it works that's fine I guess. I was kind of thinking
that if you didn't have the union you could avoid having
subsections entirely.

On Arm we don't try to save space in the CPU struct by
using unions, even though some fields are A-profile
specific and some are R or M-profile specific.

-- PMM