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

[Cédric Le Goater]

On 06/28/2018 01:40 PM, Andrea Bolognani wrote:
> On Thu, 2018-06-28 at 12:04 +0200, Cédric Le Goater wrote:
>> On 06/28/2018 10:00 AM, Andrea Bolognani wrote:
>>> On Thu, 2018-06-28 at 13:59 +1000, David Gibson wrote:
>>>> Well.. sure.. but it doesn't.  pSeries is a virtual platform, so we
>>>> have a reasonable amount of flexibility to define it as we want.
>>>> PowerNV is an emulation of existing hardware which has a specific
>>>> behaviour which we need to match.
>>>
>>> Sure, that's something to keep in mind.
>>>
>>> But the thing is, you still need to have *some* flexibility in
>>> the number of PHBs, since there is variation among real Power8
>>> and Power9 chips; in the current incarnation, that flexibility
>>> is provided by the num_phbs parameter, which is an entirely new
>>> interface that's exclusive to PowerNV.
>>>
>>> What I'm suggesting is that the same amount of flexibility is
>>> offered through a standard interface, namely -device, instead.
>>
>> Yes. I don't know to be honest. Adding support for -device is not 
>> complex.
>>
>> v2 proposes to initialize a fixed set of PHBs 2, 3, 4 depending on 
>> the CPU. I think this is the best modeling option to fit the HW.
> 
> That approach would require even more hacks in libvirt if we ever
> wanted to support PowerNV - basing the PCI address allocation on
> the CPU model is not something that's really ever happened before.

ah. hmm, so that's another +1 for the -device approach.

> To make it somewhat reasonable, information about the number of
> PHBs created for each CPU model would have to be exposed through
> QMP. And I wonder what a multi-chip guest would look like...
> 
> Plus, as soon as you try something like
> 
>   $ qemu-system-ppc64 \
>     -nodefaults -display none \
>     -machine powernv -cpu POWER8E \
>     -device pci-bridge,id=pci.1,chassis_nr=1,bus=pci.0,addr=0x1 \
>     -device megasas,id=scsi0,bus=pci.1,addr=0x1
> 
> very interesting things will start happening :)

Well it boots :)


/ # lspci 
0000:00:00.0 PCI bridge: IBM POWER8 Host Bridge (PHB3)
0000:01:00.0 PCI bridge: Red Hat, Inc. QEMU PCI-PCI bridge
0000:02:01.0 PCI bridge: Red Hat, Inc. QEMU PCI-PCI bridge
0000:02:02.0 Ethernet controller: Intel Corporation 82540EM Gigabit Ethernet 
Controller (rev 03)
0000:02:07.0 USB controller: NEC Corporation uPD720200 USB 3.0 Host Controller 
(rev 03)
0001:00:00.0 PCI bridge: IBM POWER8 Host Bridge (PHB3)
0001:01:00.0 PCI bridge: Red Hat, Inc. QEMU PCI-PCI bridge
0001:02:01.0 RAID bus controller: LSI Logic / Symbios Logic MegaRAID SAS 1078


C.