[igt-dev] [RFC] IGT device scanning and selection

[Arkadiusz Hiler]

On Tue, Jun 04, 2019 at 08:09:55AM +0000, Kempczynski, Zbigniew wrote:
> Hi all.
> 
> IGT device management is a little bit old. More than one GPU on the machine 
> are available on the market from years so there's time to propose new device
> management in IGT.
> 
> Selection using bus-device or functional specifiers.
> ---
> 1. bus-device selection
>    Current devices are mostly PCI-Express devices, but we should be able to
>    open to specify device using any bus selection. For example:
>    --device PCI:00:02.0
>    would select PCI device on 00 bus, 02 device and function 0.
> 
>    --device USB:002:003
>    would select device 003 on bus 002.
>   
>    Future buses can be specified by extending --device argument parsing.
> 
> 2. Functional selection
>    CI environments shouldn't rely on bus-device. Same devices (GPUs) may be 
>    inserted into different slots so functional selection is required. 
>    
>    Let's imagine machine have 5 cards:
>    00:02:0 - VendorX, product: A
>    00:03:0 - VendorY, product: B
>    00:04:0 - VendorX, product: A
>    00:05:0 - VendorY, product: C
>    00:06:0 - VendorX, product: D
> 
>    We should be able to select same device regardless order on the bus.
>    For example:
>    --device VendorX:A 
>    --device VendorX:A:0 
>    will select first A card of VendorX
> 
>    --device VendorY:A:1
>    will select second A card of VendorX
> 
>    If vendor would like to have its own parsing method for the product
>    overriding parsing will be possible. For example:
>    --device VendorX:GPU-Card:0
>    VendorX must then register its own function to handle 'GPU-Card:0'
>    string on his own. 
> 
> ===
> 
> Device management
> ---
> New device management should allow user to see current devices. 
> I propose IGT tool called 'lsgpu' which would discover devices in 
> any registered bus topologies scanning methods.

Hey,

Seems like a well-written verbalization of some of the ideas that were
floating around since XDC. Thanks!


Couple of points that were not captured here:

1. We should have an option to set device via .igtrc and IGT_DEVICE env
variable too. ENV variable would take precedence over .igtrc, and
--device switch would take precedence over both of the other methods.

That would help a lot with both automatization and having some defaults
for local development.


2. What to do with drm_open_driver(DRIVER_INTEL) et al?

Simplest solution would be to just skip if we are --device-ing a card
that does not meet those "constraints", but we may want to rework those
a bit?

3. VKMS and VGEM?


I have also CCed people that may be interested in running IGT with
multiple GPUs and may something to say.

Cheers,
Arek