Re: [Qemu-devel] [RFC v1 1/2] arm: Add the cortex-a9 CPU to the a9mpcore device

[Andreas Färber]

Am 16.06.2014 12:34, schrieb Peter Crosthwaite:
> On Mon, Jun 16, 2014 at 8:19 PM, Andreas Färber <address@hidden> wrote:
>> However a more fundamental issue that PMM was unsure about is whether
>> the CPUs should be child<> of MPCore as done here or a sibling of the
>> MPCore container.
>>
> 
> I'll go with child. The CPU does not exist outside the MPCore. They
> are a heirachy, not-peers and the qom-composition should reflect that.

Well, for Cortex-A9 that may work. But Cortex-A15 (and Cortex-A5x if
existant by now) should also be refactored alongside, as proof of
concept - can you really create num_cpu cortex-a15 CPUs on the MPCore
for a big.LITTLE configuration? I'd be really surprised if there were
separate MPCore devices per cluster. That would then indicate that the
homogeneity assumption among CPUs within an MPCore is wrong and we need
to let its parent create the CPUs rather than an MPCore property.

Besides, not all CPUs have an MPCore, Cortex-A8 and Cortex-A5 come to
mind, so we should be aware that ARMCPU child<>s on the MPCore will lead
to asymmetry between SoCs. But that shouldn't stop proper Cortex-A9/-A15
modeling, just like Quark and Baytrail SoCs will inevitably lead to
modeling differences in the PC world.

Regards,
Andreas

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