Re: [PATCH 3/5] hw/cpu/cluster: Restrict CPU cluster to a particular CPU type

[Peter Maydell]

On Thu, 16 Feb 2023 at 14:23, Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
>
> CPU cluster id is used by TCG accelerator to "group" CPUs
> sharing the same ISA features, so TranslationBlock can be
> shared between the cluster (see commit f7b78602fd "accel/tcg:
> Add cluster number to TCG TB hash"). This mean we shouldn't
> mix different kind of CPUs into the same cluster.
>
> Enforce that by adding a 'cpu-type' property. The cluster's
> realize() method will check all children are of that 'cpu-type'
> class.
>
> If the property is not set, the first CPU added to a cluster
> sets its CPU type, and only that type fo CPU can be added.

This seems like a reasonable extra assertion to add.
It won't catch all accidental "wrong thing put into
cluster" bugs (you can still put two differently
configured CPUs of the same type in a cluster) but it's
better than nothing.

Personally I think I would just have the "check they're
all the same type" guard, rather than having the board
code set a property explicitly.

thanks
-- PMM