RE: [PATCH 6/6 v3] PCI: document the change

Dong, Eddie
2008-10-14T00:23:44Z

Matthew Wilcox wrote:

> Wouldn't it be more useful to have the iov/N directories
> be a symlink to the actual pci_dev used by the virtual
> function?

The main concern here is that a VF may be disabed such as when PF enter
D3 state or undergo an reset and thus be plug-off, but user won't
re-configure the VF in case the PF return back to working state.

>
>> +For network device, there are:
>> + - /sys/bus/pci/devices/BB:DD.F/iov/N/mac
>> + - /sys/bus/pci/devices/BB:DD.F/iov/N/vlan
>> + (value update will notify PF driver)
>
> We already have tools to set the MAC and VLAN parameters
> for network devices.

Do you mean Ethtool? If yes, it is impossible for SR-IOV since the
configuration has to be done in PF side, rather than VF.

>
> I'm not 100% convinced about this API. The assumption
> here is that the driver will do it, but I think it should
> probably be in the core. The driver probably wants to be

Our concern is that the PF driver may put an default state when it is
loaded so that SR-IOV can work without any user level configuration, but
of course the driver won't dynamically change it.
Do u mean we remove this ability?

> notified that the PCI core is going to create a virtual
> function, and would it please prepare to do so, but I'm
> not convinced this should be triggered by the driver.
> How would the driver decide to create a new virtual
> function?
>
>
> From my reading of the SR-IOV spec, this isn't how it's
> supposed to work. The device is supposed to be a fully
> functional PCI device that on demand can start peeling
> off virtual functions; it's not supposed to boot up and
> initialise all its virtual functions at once.

The spec defines either we enable all VFs or Disable. Per VF enabling is
not supported.
Is this what you concern?

Thanks, eddie