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Re: [Qemu-devel] [PATCH v1 3/4] hw: Deduce the default machine from the
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [PATCH v1 3/4] hw: Deduce the default machine from the specified CPU model |
Date: |
Tue, 28 Aug 2012 13:58:22 +0100 |
User-agent: |
KMail/1.13.7 (Linux/3.2.0-3-amd64; KDE/4.8.4; x86_64; ; ) |
> > This changes the driver behavior to choose the default machine
> > model based on the CPU being used. Defaulting the machine this
> > way makes it easier to use QEMU as an ISS by just specifying
> > the -cpu option since a default machine that is suitable for
> > emulating the full ISA can be chosen.
> >
> > For example, currently on ARM the ARM Integrator/CP board is
> > chosen as the default machine when specifying just a CPU.
> > However, this doesn't work well when passing -cpu cortex-m3
> > since on ARMv7-M processors the NVIC is a part of the architecture
> > and is needed to support instructions like SVC.
>
> Personally I'd rather we didn't support a "default machine" at
> all, at least for ARM. It does matter what board you run on,
> so you need to specify.
A possible compromise is to only accept -cpu if -M is also specified.
> Just to pick an obvious example, you can't stick a core
> which supports VFPv4 (the A15 is the only one we have) into
> the integratorcp
Yes you can.
Your OS probably doesn't support it, and you might have trouble persuading the
OS vendor to support something that doesn't physically exist, but those are a
competely separate problems.
> We could reasonably add patches which made boards error
> out if you tried to use them with unsupported CPUs, I guess.
That suffers from a large fuzzy region containing interesting combinations
that could/do work, but will probably never be created in silicon.
If done properly this the QOM conversion should give you this for free.
Paul
[Qemu-devel] [PATCH v1 4/4] hw: Add support for a dummy ARMv7-M board, Meador Inge, 2012/08/27