On Fri, 2018-10-12 at 16:04 +0100, Daniel P. Berrangé wrote:
On Fri, Sep 28, 2018 at 04:46:13PM +0800, Yi Min Zhao wrote: [...]
<hostdev mode='subsystem' type='pci'> <driver name='vfio'/> <source> <address domain='0x0001' bus='0x00' slot='0x00' function='0x0'/> </source> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'> <zpci uid='0x0003' fid='0x00000027'/> </address> </hostdev>
I'm not sure if this was discussed in earlier versions, but to me this use of a child element looks wrong.
What we're effectively saying is that s390 has a different addressing scheme. It happens to share some fields with the current PCI addressing scheme, but it is none the less a distinct scheme.
IOW, I think it should be
<address type='zpci' domain='0x0000' bus='0x00' slot='0x01' function='0x0' uid='0x0003' fid='0x00000027'/>
Of course internally we can still share much logic for assigning the addreses between "pci" and "zpci".
So what happens with PCI devices on s390 is that *two* devices will be added to the guest: one is the usual virtio-net-pci or what have you, which has its own PCI address allocated using the same algorithm as other architectures; the other one is a '-device zpci', which IIUC works basically like an adapter between the PCI device itself and the guest OS, and which is identified using uid and fid. Calling it a completely different address type seems like a bit of a stretch: there is definitely a PCI address involved, which is why the zPCI part was implemented through a potentially reusable "PCI address extension" mechanism. -- Andrea Bolognani / Red Hat / Virtualization