On 02/13/2011 09:56 AM, Avi Kivity wrote:
On 02/13/2011 05:38 PM, Anthony Liguori wrote:
2) get rid of the entire concept of machines. Creating a i440fx is
essentially equivalent to creating a bare machine.
No, it's not. The 440fx does not include an IOAPIC, for example.
There may be other optional components, or differences in wiring,
that make two machines with i440fx not identical.
The IOAPIC is basically the only other component and I view it as
part of the CPU interface to the chipset.
But it isn't. The IOAPIC is not per-core or per-socket.
Yeah, I wasn't implying that it was.
It's strictly board level. It's a board interface to the cpu.
But still, if we're creating a machine from scratch:
qemu -device i440fx,id=nb -device piix3,id=sb,chipset=nb -device
ioapic,id=ioapic,chipset=sb -device cpu,ioapic=ioapic,northbridge=nb
Is not all that unreasonable and presents a fully functioning PC.
Sure. And -M blah is a shortcut.
Exactly. Or better yet, blah is a config file that contains
[device "nb"]
driver=i440fx
[device "sb"]
driver=piix3
chipset=nb
[device "ioapic"]
driver=ioapic
chipset=sb
[device "cpu"]
driver=cpu
ioapic=ioapic
northbridge=nb
4) model the CPUs as devices that take a pointer to a host
controller, for x86, the normal case would be giving it a pointer
to i440fx.
Surely the connection is via a bus? An x86 cpu talks to the bus,
and there happens to be an 440fx north bridge at the end of it. It
could also be a Q35 or something else.
I see being on a bus as really just taking a pointer to an
interface. So yes, the i440fx would implement a PentiumCpuInterface
or something like that and the CPU would take a pointer to a
PentiumCpuInterface[1].
This is part of why having proper polymorphism is important. We need
it in order to be able to express concepts like interfaces.
The CPUs and northbridge are peers on the system bus. However, this
isn't something good to model, since it keeps changing without any
guest software impact.
If we can move away from Bus abstraction and to a simpler interface
mechanism, then we can express peer relationships by just having
bidirection references. IOW:
-device cpus,northbridge=nb,id=cpus,count=16 -device i440fx,cpus=cpus
I don't think modelling each CPU makes sense. We should probably just
model all cpus in a single device for the sake of simplicity.
Regards,
Anthony Liguori
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