On Mon, 7 Jun 2021 09:36:38 +0800 Yunsheng Lin wrote:

On 2021/6/5 2:41, Jakub Kicinski wrote:

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On Fri, 4 Jun 2021 09:18:04 +0800 Yunsheng Lin wrote:  

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My initial thinking is a id from a global IDA pool, which indeed may
change on every boot.

I am not really thinking much deeper about the controller id, just
mirroring the bus identifiers for pcie device and ifindex for netdev,  

devlink instance id seems fine, but there's already a controller
concept in devlink so please steer clear of that naming.  

I am not sure if controller concept already existed is reusable for
the devlink instance representing problem for multi-function which
shares common resource in the same ASIC. If not, we do need to pick
up other name.

Another thing I am not really think throught is how is the VF represented
by the devlink instance when VF is passed through to a VM.
I was thinking about VF is represented as devlink port, just like PF(with
different port flavour), and VF devlink port only exist on the same host
as PF(which assumes PF is never passed through to a VM), so it may means
the PF is responsible for creating the devlink port for VF when VF is passed
through to a VM?

Or do we need to create a devlink instance for VF in the VM too when the
VF is passed through to a VM? Or more specificly, does user need to query
or configure devlink info or configuration in a VM? If not, then devlink
instance in VM seems unnecessary?

I believe the current best practice is to create a devlink instance for
the VF with a devlink port of type "virtual". Such instance represents
a "virtualized" view of the device.

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which may change too if the device is pluged into different pci slot
on every boot?  

Heh. What is someone reflashes the part to change it's serial number? :)
pci slot is reasonably stable, as proven by years of experience trying
to find stable naming for netdevs.  

I suppose that requires a booting to take effect and a vendor tool
to reflash the serial number, it seems reasonable the vendor/user will
try their best to not mess the serial number, otherwise service and
maintenance based on serial number will not work?
I was thinking about adding the vendor name besides the serial number
to indicate a devlink instance, to avoid that case that two hw from
different vendor having the same serial number accidentally.

I'm not opposed to the use of attributes such as serial number for
selecting instance, in principle. I was just trying to prove that PCI
slot/PCI device name is as stable as any other attribute. 

In fact for mass-produced machines using PCI slot is far more
convenient than globally unique identifiers because it can be used 
to talk to a specific device in a server for all machines of a given
model, hence easing automation.

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We could still allow devlink instances to have multiple names,
which seems to be more like devlink tool problem?

For example, devlink tool could use the id or the vendor_info/
serial_number to indicate a devlink instance according to user's
request.  

Typing serial numbers seems pretty painful.
  

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Aliase could be allowed too as long as devlink core provide a
field and ops to set/get the field mirroring the ifalias for
netdevice?  

I don't understand.  

I meant we could still allow the user to provide a more meaningful
name to indicate a devlink instance besides the id.

To clarify/summarize my statement above serial number may be a useful
addition but PCI device names should IMHO remain the primary
identifiers, even if it means devlink instances with multiple names.

In addition I don't think that user-controlled names/aliases are
necessarily a great idea for devlink.