[libvirt] [PATCH v3 01/12] conf: Add definitions for 'uid' and 'fid' PCI address attributes

[Andrea Bolognani]

On Tue, 2018-08-21 at 17:35 +0800, Yi Min Zhao wrote:
> I want to ask a question. For pci address, any pci device can't use slot 0.
> Is that a reason why PCI part could treat all zeros as empty address?

A PCI address where all attributes are zero can't be used, so
there's no ambiguity there; same for a zPCI address where all
attributes are zero, which also can't be used.

> For zPCI address, if we use the same strategy as PCI part and user
> wants to assign fid=0 to the specific device, he might encounter
> assignment failure. At least, according to the doc, 0 shoud be a valid
> value to assign to fid.

If the user wants to use a specific zPCI address they can simply
specify both attributes, eg. uid=1,fid=0 will work just fine with
the proposed approach and won't produce errors or cause a new zPCI
address to be automatically assigned.

If the user only specified fid=0 while leaving uid unspecified,
well, an address is going to be picked for them. This is consistent
with how PCI addresses are treated so it shouldn't be a problem: if
anything, *deviating* from this behavior would cause confusion.

-- 
Andrea Bolognani / Red Hat / Virtualization