Re: [pve-devel] [PATCH RFC container] Add device passthrough

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

Am 20/10/2023 um 09:51 schrieb Dominik Csapak:
> On 10/20/23 09:08, Wolfgang Bumiller wrote:
>> Also, Dominik recently added resource mappings for qemu for USB & PCI.
>> PCI might be tricky, but for USB we may be able to use these mappings as
>> well.
>> That said, "raw" `/dev` node pass-through still makes sense as a
>> separate thing for containers anyway since raw `lxc....` entries in the
>> container config can currently be very inconvenient to deal with
>> particularly with unprivileged containers (read on below for why...)
> 
> just to chime in here, i don't think it'll be easily possible to reuse
> the pci/usb maps as is since we'd have to map from pciid /usb-vendor/device
> (or path) to a device node? i don't think thats generally possible, since
> the driver does not always make that info easily available
> (e.g. multi gpu setup and /dev/dri/cardX, or usb-to-serial adapters
> and /dev/ttySX ?) i guess it could work, but we probably would have
> to implement that for every driver out there?
> 

USB should be workable via resolving to /dev/bus/usb/*, PCI could be,
theoretically, but isn't now and probably won't be anytime soon – i.e.,
as Wolfgang mentioned off list, there's a reason that there's no
/dev/bus/pci/

> what i would like to see however is to integrate a new type of mapping
> for container devices specifically so that the ux is the same
> (create mappings for whole cluster, assigning privileges, etc)

I'd try hard to re-use the USB mappings, those seem to be one of the
most common pass-through setups for containers (e.g., for those
home automation zigbee/matter/... adapters, or in some countries DVB-T
ones, be it for TV or ADS-B plane tracking).

If we can make USB work then we'd have the basic concept of attaching
a mapping done, adding a new type of (block/char) device mapping could
then be an independent task for later to keep scope a bit smaller.

Fixing Wolfgang's comments for workable pass-through for unprivileged
containers is probably the most important change needed for now.

I'd then even be open to apply this with (root@pam only!) absolute
path to /dev support only, but IMO resolving the mapping itself should
not be too hard, so if using /dev/bus/usb/ works having that in there
from the start would be definitively nice.