Re: [Qemu-devel] [PATCH v2 1/2] ppc/pnv: Add model for Power8 PHB3 PCIe Host bridge

[Cédric Le Goater]

On 07/27/2018 10:43 AM, Benjamin Herrenschmidt wrote:
> On Fri, 2018-07-27 at 10:25 +0200, Cédric Le Goater wrote:
>> Each PHB creates a pci-bridge device and the PCI bus that comes with it. 
>> It makes things easier to define PCI devices. 
>>
>> It is still quite complex ... Here is a sample :
>>
>> qemu-system-ppc64 -m 2G -machine powernv \
>>   -cpu POWER8 -smp 2,cores=2,threads=1 -accel tcg,thread=multi \
>>   -kernel ./zImage.epapr -initrd ./rootfs.cpio.xz -bios ./skiboot.lid \
>>   \
>>   -device megasas,id=scsi0,bus=pci.0,addr=0x1 \
>>   -drive 
>> file=./rhel7-ppc64le.qcow2,if=none,id=drive-scsi0-0-0-0,format=qcow2,cache=none
>>  \
>>   -device 
>> scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0,bootindex=2
>>  \
>>   \
>>   -device ich9-ahci,id=sata0,bus=pci.1,addr=0x1 \
>>   -drive 
>> file=./ubuntu-ppc64le.qcow2,if=none,id=drive0,format=qcow2,cache=none \
>>   -device ide-hd,bus=sata0.0,unit=0,drive=drive0,id=ide,bootindex=1 \
>>   -device e1000,netdev=net0,mac=C0:FF:EE:00:00:02,bus=pci.1,addr=0x2 \
>>   -netdev bridge,helper=/usr/libexec/qemu-bridge-helper,br=virbr0,id=net0 \
>>   -device nec-usb-xhci,bus=pci.1,addr=0x7 \
> 
> I don't understand why. That means you can't put emulated (or real)
> PCIe device below it ?

Well, skiboot does seem to find them. But that's not a good reason.
I will dig in.

> Why force them down the path of having a bridge to legacy PCI always ?
>
> My original intent was to have one such bridge in a machine for the
> various default PCI devices qemu has that aren't (yet) PCIe (and also
> for testing :-) but I never thought we'd throw one onto every PCIe bus.

OK. Let's get of rid it and let's find why the FW doesn't see the PCIe
devices.

Thanks,

C.