Re: [Qemu-arm] [PATCH v3 7/7] raspi: add raspberry pi 2 machine

[Andrew Baumann]

Hi Peter,

> From: Peter Crosthwaite [mailto:address@hidden
> Sent: Tuesday, 12 January 2016 16:44
> On Tue, Jan 12, 2016 at 3:53 PM, Andrew Baumann
> <address@hidden> wrote:
> >> From: Peter Crosthwaite [mailto:address@hidden
> >> Sent: Monday, 11 January 2016 19:58
> >> > +    /* Allocate and map RAM */
> >> > +    memory_region_allocate_system_memory(&s->ram,
> >> OBJECT(machine), "ram",
> >> > +                                         machine->ram_size);
> >> > +    memory_region_add_subregion_overlap(get_system_memory(), 0,
> >> &s->ram, 0);
> >>
> >> I thought the SoC handled this now? Why do you need to add to
> >> system_memory?
> >
> > If I don't map it here, how do RAM accesses from the CPUs work?
> >
> 
> Do the CPUs not have their AS'es connected to your custom ASes by the SoC
> layer?
> 
> > Or are you saying that I should still do this, but do it in the SoC not the
> board level?
> >
> 
> I was hoping we could get away with 0 use of system_memory.

On further investigation, I don't think it's possible to wire up CPU ASes 
explicitly. There's no obvious property to set. Each cpu->as is initialised to 
point to address_space_memory at the top of cpu_exec_init(), and there is no 
way I could see to override that.

I think what I have now is pretty clean, but if you'd prefer to do the mapping 
at into the global AS at SoC level that's fine with me too.

Thanks,
Andrew