Re: Xen with libvirt and SR-IOV
On 3/21/23 11:05, nospam(a)godawa.de wrote:
Hi everybody,
since long time, I'm using Xen on CentOS with XL, currently latest CentOS 7 with
Xen 4.15 from the CentOS-Xen-Project. For several VMs I have to use SR-IOV, to
lower the CPU-usage on Dom0 on the host.
CentOS 7 comes to an end, Xen is not supported by RHEL nor RockyLinux anymore,
so unfortunately I have to switch to KVM.
First step will be now, converting all the scripts for managing and running VMs,
that they run with the additional libvirt-layer.
What is the libvirt version?
Mostly everything is working, but I do not get a network interface in
the VM,
when I start it with "virsh start ..." instead of "xl create ...".
First of all, is there documentation how to configure the VMs in the
dom-definition for XEN (all docs I found are KVM-related)?
I know it's not complete, but https://libvirt.org/formatdomain.html makes an
attempt to identify hypervisor support for the various configuration settings.
The converted xl-config does not do the job:
virsh -c xen:/// domxml-from-native --format xen-xl vm > vm.xml
These are some none working examples I tried out:
...
<interface type='hostdev' managed='yes'>
<mac address='02:16:32:10:20:30'/>
<driver name='xen'/>
<source>
<address type='pci' domain='0x0000' bus='0x81'
slot='0x02'
function='0x6'/>
</source>
<vlan>
<tag id='11'/>
</vlan>
</interface>
...
...
<hostdev mode='subsystem' type='pci' managed='yes'>
<driver name='xen'/>
<source>
<address domain='0x0000' bus='0x81' slot='0x02'
function='0x6'/>
</source>
<address type='pci' domain='0x0000' bus='0x81'
slot='0x02' function='0x6'/>
</hostdev>
...
I've used both configurations successfully. Has the sriov virtual function been
unbound from the native driver and bound to xen-pciback? You can check which
driver is in use with something like
ls /sys/bus/pci/devices/0000\:81\:02.6/driver
If bound to xen-pciback, it vf should also appear in the output of 'xl
pci-assignable-list'.
Regards,
Jim