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PCI-PT ports association & pci_alias

asked 2017-01-25 03:18:00 -0600

updated 2017-01-25 03:19:54 -0600

Hi, I am currently playing with PCI Passthrough VMs.

The compute node has 4 identical PCI-PT ports (2 NICs with 2 10Gb ports, Intel). I configured the pci_alias = {"vendor_id": "8086", "product_id": "10fb", "name":"intel_pt"} and configured a corresponding flavor with nova flavor-key VNF.4PCIPT set "pci_passthrough:alias"="intel_pt:4"

I always create the VM with an heat template, verifying that all vNICS are always mapped to PCI-PT ports in the same order (lower addr bus - higher port number is the first one, followed by lower addr bus - higher port number -1)

e.g.:

0000:03:00.1

0000:03:00.0

0000:04:00.1

0000:04:00.0

Is there anyone that could confirm this behaviour, in order to be sure it is deterministic. Where could I search for the logic behind this behaviour?

Another approach to specifically map PCI-PT devices to vNICs could be to define a specific pci_alias that maps specifically to a predefined port. Could it be possible to define a pci_alias referring to 0000:04:00.1 port only (assuming all NIC ports are identical, both from vendor and product IDs perspective)

Thanks in advance

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answered 2017-02-17 02:23:25 -0600

It seems it is related to the way you insert the values in nova.conf file.

Add the first interface (int1) in nova.conf
restart nova 
create a VM that uses that interface [here VM NIC 1 is mapped to int1]
delete the VM
add up in nova.conf file the second one (int2)
restart nova
create a VM that uses those interfaces [here VM NIC 1 is mapped to int2 and VM NIC 2 is mapped to int1]
delete the VM
add up in nova.conf file the third one (int3)
restart nova
create a VM that uses those interfaces [here VM NIC 1 is mapped to int3, VM NIC 2 is mapped to int2 and VM NIC 3 is mapped to int1]
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Asked: 2017-01-25 03:18:00 -0600

Seen: 104 times

Last updated: Feb 17