[openstack-dev][PCI passthrough] How to use PCI passthrough feature correctly? And is this BUG in update_devices_from_hypervisor_resources?

Sean Mooney smooney at redhat.com
Wed Mar 1 08:15:16 UTC 2023


On Wed, 2023-03-01 at 15:20 +0800, Simon Jones wrote:
> BTW, this link (
> https://docs.openstack.org/neutron/latest/admin/ovn/smartnic_dpu.html) said
> I SHOULD add "remote_managed" in /etc/nova/nova.conf, is that WRONG ?

no its not wrong but for dpu smart nics you have to make a choice when you deploy
either they can be used in dpu mode in which case remote_managed shoudl be set to true
and you can only use them via neutron ports with vnic-type=remote_managed as descried in that doc
https://docs.openstack.org/neutron/latest/admin/ovn/smartnic_dpu.html#launch-an-instance-with-remote-managed-port


or if you disable dpu mode in the nic frimware then you shoudl remvoe remote_managed form the pci device list and
then it can be used liek a normal vf either for neutron sriov ports vnic-type=direct or via flavor based pci passthough.

the issue you were havign is you configured the pci device list to contain "remote_managed: ture" which means
the vf can only be consumed by a neutron port with vnic-type=remote_managed, when you have "remote_managed: false" or unset
you can use it via vnic-type=direct i forgot that slight detail that vnic-type=remote_managed is required for "remote_managed: ture".


in either case you foudn the correct doc https://docs.openstack.org/neutron/latest/admin/ovn/smartnic_dpu.html
neutorn sriov port configuration is documented here https://docs.openstack.org/neutron/latest/admin/config-sriov.html
and nova flavor based pci passthough is documeted here https://docs.openstack.org/nova/latest/admin/pci-passthrough.html

all three server slightly differnt uses. both neutron proceedures are exclusivly fo network interfaces.
https://docs.openstack.org/neutron/latest/admin/ovn/smartnic_dpu.html requires the use of ovn deployed on the dpu
to configure the VF contolplane. https://docs.openstack.org/neutron/latest/admin/config-sriov.html uses the sriov nic agent
to manage the VF with ip tools. https://docs.openstack.org/nova/latest/admin/pci-passthrough.html is intended for pci passthough
of stateless acclerorators like qat devices. while the nova flavor approch cna be used with nics it not how its generally 
ment to be used and when used to passthough a nic expectation is that its not related to a neuton network.




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