Re: QEMU/KVM [RFC]: add support for 128 PCI slots

[Marcelo Tosatti <mtosatti@redhat.com>]

On Fri, Apr 25, 2008 at 11:38:21AM +0200, Alexander Graf wrote:
> 
> On Apr 25, 2008, at 3:01 AM, Marcelo Tosatti wrote:
> 
> >
> >Add three PCI bridges to support 128 slots. Vendor and device_id have
> >been stolen from my test box.
> >
> >I/O port addresses behind each bridge are statically allocated  
> >starting
> >from 0x2000 with 0x1000 length. Once the bridge runs out of I/O space
> >the guest (Linux at least) happily allocates outside of the region.  
> >That
> >needs verification.
> >
> >I/O memory addresses are divided between 0xf0000000 -> APIC base.
> >
> >The PCI irq mapping function is also changed, there was the assumption
> >that devices behind the bridge use the IRQ allocated to the bridge
> >device itself, which is weird. Apparently this is how the SPARC ABP  
> >PCI
> >host works (only user of the bridge code at the moment).
> 
> Is there any reason we're not using the _PIC function and give the OS  
> a clue on which APIC pin the device is? Right now everything boils  
> down to LNKA - LNKD which it does not have to.
> It might even be a good idea to connect each PCI device to a specific  
> APIC pin, so we don't need to share too much, which might become a  
> problem with a lot of PCI devices. As far as I know there is no  
> limitation on how many pins an APIC may have.

I was not aware of the _PIC function. Will take a look at it.

The number of IRQ's certainly needs to increase.

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