Question

I am using KVM on Centos 7. I have created a VM with SR-IOV VFs to pass traffic. I notice that I am unable to pass traffic when I tag the interface inside the VM. I have read through the internet and the data sheet from Intel but none give me a clear picture of how it is done.

Server1

Eth0 – PF

SR-IOV Enabled

eth0-vf-1 (Attached to VM)

[Inside the VM]

Centos 7

eth0.100

Server2

Eth0 – PF

SR-IOV Enabled

eth0-vf-1 (Attached to VM)

[Inside the VM]

Centos 7

eth0.100

Switch

Extreme Networks

VLAN tagged 100

Port 1,2

Port 1 – Server 1 – Eth0 – PF

Port 2 – Server 2 – Eth0 – PF

Can anyone guide me through this? I would like to know if anyone has tried such a configuration or would this not be the best used case for SR-IOV?

I did find one issue here but did not understand much. Thank you community.

Does it work for you or doesn’t it? It definitely should, if the switch is configured properly — dyasny, Sep 29, 2016 at 13:40
It does not work for me. I was wondering if anyone every tried using multiple vlans on a VF inside a VM? — Centos Newbie, Oct 1, 2016 at 12:55

dyasny · Accepted Answer · 2016-10-03 14:04:42Z

I checked, and it looks like with VFs, the tagging needs to be done on the host, via libvirt. The way this looks in the domxml is as follows

<interface type='hostdev' managed='yes'>                                                         
  <mac address=' fa:aa:aa:aa:aa:aa '/>                                                              
  <driver name='kvm'/>                                                                           
  <source>                                                                                       
    <address type='pci' domain='0x0000' bus='0x02' slot='0x00' function='0x7'/>                  
  </source>                                                                                      
  <vlan>                                                                                          
    <tag id='190'/>                                                                              
  </vlan>
  <alias name='hostdev0'/>
  <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
</interface>

Link: https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Virtualization_Host_Configuration_and_Guest_Installation_Guide/sect-Virtualization_Host_Configuration_and_Guest_Installation_Guide-SR_IOV-How_SR_IOV_Libvirt_Works.html

yes, you can tag inside a VM with a regular virtio NIC or with a regular PCI-passthrough card, but not with SRIOV — dyasny, Oct 3, 2016 at 14:57
After a lot of digging I find your inputs True! Thanks for the prompt answer. You can’t tag inside the VM while using SR-IOV — Centos Newbie, Oct 12, 2016 at 3:51
this is in direct conflict if what is stated here: communities.intel.com/thread/52257 — Andre de Miranda, Nov 13, 2016 at 12:49
interesting. I got my information directly from folks working on implementing SRIOV in openstack nova, they should know what they are talking about. The link to the official documentation also points toward my solution. There may be more than one correct answer here, but the o/p confirmed tagging inside the VM didn’t work for him — dyasny, Nov 15, 2016 at 1:03

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