[Skiboot] Skiboot on qemu questions

[Oliver O'Halloran]

On Fri, Oct 9, 2020 at 1:51 PM Marty E. Plummer <hanetzer at startmail.com> wrote:
>
> Hello all.
>
> Once again dusting off my coreboot work, making fairly good progress I
> think (at least when running against a virtualized system via LeGoater's
> qemu powernv target) and was a bit curious about a few things.
>
> In the context of running skiboot in qemu, is it 'considered' emulated?
> As in, will it hit hypervisor exceptions? Currently I'm catching
> excpetions 0xe00 and 0xe40 when jumping from romstage to ramstage, which
> are both hypervisor exceptions. Wondering if I should be worried about
> this. What about skiboot on real hardware?

The powernv model emulates real hardware. When entering skiboot the
CPU is in hypervisor real mode so illegal instructions will trap to
0xe40 to allow the hypervisor (that'd be you in this case) to emulate
the instruction if it wants to. You shouldn't be taking a HDSI (0xe00)
unless you turned on the MMU though so that's a bit odd. If the MMU is
off it might be a bug in the model.

> Some info and teaserish: https://i.imgur.com/07d2Q0y.png
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