Instance (vm guest) not getting PCI card

Sean Mooney smooney at
Tue Jul 2 20:36:32 UTC 2019

On Tue, 2019-07-02 at 15:51 -0400, Mauricio Tavares wrote:
> Newbie and easy questions: I have two cards, one in each stein
> (centos) compute node setup for kvm, which I want to be able to handle
> to a vm guest (instance). Following
>, I
> 1. Setup both computer nodes to vt-t and iommu.
> 2. On the controller
> 2.1. Create a PCI alias based on the vendor and product ID
> alias = { "vendor_id":"19fg", "product_id":"4000",
> "device_type":"type-PF", "name":"testnic" }
the alias looks correcect. assuming you have it set in teh pci section
then i should generate teh request of a pci device.

the alias needs to be defiend in the nova.conf used by the api node and the compute node
for it to work correctly but i assume that when you say its set on the contoler it set on
the nova.conf the nova api is useing.
> - The PCI address for the card is different on each compute node
> 2.2. Create a flavor, say, n1.large
> openstack flavor create n1.large --id auto --ram 8192 --disk 80
> --vcpus 4 --property "pci_passthrough:alias"="testnic:1"
this is also correct

> 2.3. Restart openstack-nova-api
> 3. On each compute node
> 3.1. Create a PCI alias based on the vendor and product ID
> alias = { "vendor_id":"19fg", "product_id":"4000",
> "device_type":"type-PF", "name":"testnic" }
> 3.2. Create passthrough_whitelist entry
> passthrough_whitelist = { "vendor_id":"19fg", "product_id":"4000" }
assuming this is set in the pci section it also looks correct
> 3.3. Restart openstack-nova-compute
> 4. Create instance (vm guest) using the n1.large flavor.
> 5. Login to instance and discover dmesg and lspci does not list card
> 6. Do a "virsh dumpxml" for the instance on its compute node and
> discover there is no entry for the card listed in the xml file. I take
> nova would automagically do what I would if this was a kvm install,
> namely ensure card cannot be accessed/used by the host and then edit
> the guest xml file so it can see said card.
yes you should have seen it in the xml and the card should have been passed through to the guest.
> Questions:
> Q1: If a device is sr-iov capable, do I have to use that or can I just
> pass the entire card to the vm guest?
you can passthorugh the entire card to the guest yes.

> Q2: Is there anywhere I can look for clues to why is the libvirt xml
> file for the instance not being populated with the pci card info? So
> far I only looked in the controller node's nova_scheduler.log file.
there are several things to check.
first i would check the nova compute agenet log and see if there are any tracebacks or errors
second in the nova cell db, often called just nova or nova_cell1 (not nova_cell0) check the pci_devices
table and  see if the devices are listed.

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