Re: [kvmarm] [RFC PATCH 0/3] KVM: ARM: Get rid of hardcoded VGIC addresses

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2012-10-25 18:14, Paolo Bonzini wrote:
> Il 24/10/2012 02:50, Paul Mackerras ha scritto:
>> So we could indeed use the existing KVM_CREATE_IRQCHIP to tell KVM to
>> create a presentation controller per vcpu.  But then how do we tell
>> KVM how many source controllers we want and how many interrupts each
>> source controller should handle?  The source controllers are not tied
>> to any particular vcpu, and a source controller could potentially have
>> 100s of interrupts or more (particularly with MSIs).  Configuration of
>> each source fits into 64 bits, so if we tried to use KVM_SET_IRQCHIP
>> for configuring a source controller we'd be limited to 64 interrupts
>> per source controller.
> 
> As Jan said, there's more than a few similarities between the x86 and
> PPC model.
> 
> Taking inspiration from the x86 API, configuring the source controller
> seems to be more of a task for KVM_SET_GSI_ROUTING (a very x86-centric
> name, I must admit).

For wiring things together, I agree. But the IOAPIC has a fixed number
of input lines per chip, Power needs to configure them. I don't think
deriving this from addressed lines is the best solution. Some lines may
be configured (too) late, when the chip should have defined its
configuration already.

Jan

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