Bug 1951489

There were some patches posted on the list:

https://listman.redhat.com/archives/libvir-list/2021-July/msg00836.html

Hi Michal, do you think the steps are enough to test in on libvirt side? 
bug 1865786 comment 7 shows the method to verify the function. I will try it with windows guest. Linux guest do not support it yet now. 

Since 8.3.0 and QEMU 5.1 , rss and rss_hash_report are implemented in libvirt, refer to https://libvirt.org/formatdomain.html#setting-nic-driver-specific-options

# rpm -q libvirt qemu-kvm
libvirt-8.3.0-1.el9.x86_64
qemu-kvm-7.0.0-4.el9.x86_64

SC1: Start vm with the settings
1. Start vm with the settings:
# virsh dumpxml test | grep /interface -B8
    <interface type='bridge'>
      <mac address='52:54:00:fc:5e:27'/>
      <source bridge='br0'/>
      <target dev='vnet27'/>
      <model type='virtio'/>
      <driver queues='4' rss='on' rss_hash_report='on'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
    </interface>

# ps aux | grep rss
...
-netdev tap,fds=23:25:26:27,id=hostnet0,vhost=on,vhostfds=28:29:30:31 
-device {"driver":"virtio-net pci","mq":true,"vectors":10,"rss":true,"hash":true,"netdev":"hostnet0","id":"net0","mac":"52:54:00:fc:5e:27","bus":"pci.1","addr":"0x0"}

SC2: hotplug with the settings:
# cat interface.xml 
<interface type='network'>
  <source network='default'/>
  <model type='virtio'/>
   <driver queues='4' rss='on' rss_hash_report='on'/>
</interface>

# cat interface.xml 
<interface type='network'>
  <source network='default'/>
  <model type='virtio'/>
   <driver queues='4' rss='on' rss_hash_report='on'/>
</interface>

# virsh dumpxml test | grep /interface -B12
......
<interface type='network'>
      <mac address='52:54:00:b4:25:51'/>
      <source network='default' portid='beb6df7f-e605-4eea-8eec-ee27fa5ef159' bridge='virbr0'/>
      <target dev='vnet28'/>
      <model type='virtio'/>
      <driver queues='4' rss='on' rss_hash_report='on'/>
      <alias name='net1'/>
      <address type='pci' domain='0x0000' bus='0x03' slot='0x00' function='0x0'/>
    </interface>

SC3: Update-device, refer to bug 2082540

(In reply to yalzhang from comment #3)
> Hi Michal, do you think the steps are enough to test in on libvirt side? 

Looks good to me.

BTW: this was merged upstream as:

4e4def21d3 qemu_command: Generate cmd line for virtio-net.rss hash properties
7ab013655d qemu_capabilities: Add capability for virtio-net "rss" and "hash".
a8b1cbe77e domain_conf: Add configs for virtio net RSS and Hash report.

v8.3.0-rc1~160

and there's one follow up commit:

2df6849d78 qemu_hotplug: Deny changing @rss and @rss_hash_report attributes of virtio vNICs

v8.4.0-rc1~43

(In reply to Michal Privoznik from comment #4)
> (In reply to yalzhang from comment #3)
> > Hi Michal, do you think the steps are enough to test in on libvirt side? 
> 
> Looks good to me.
> 
> BTW: this was merged upstream as:
> 
> 4e4def21d3 qemu_command: Generate cmd line for virtio-net.rss hash properties
> 7ab013655d qemu_capabilities: Add capability for virtio-net "rss" and "hash".
> a8b1cbe77e domain_conf: Add configs for virtio net RSS and Hash report.
> 
> v8.3.0-rc1~160
> 
> and there's one follow up commit:
> 
> 2df6849d78 qemu_hotplug: Deny changing @rss and @rss_hash_report attributes
> of virtio vNICs
> 
> v8.4.0-rc1~43

Hi Michal,

This is just a basic support. Still some work is going on upstream to enable the usage with libvirt when QEMU runs without root privileges by using ebpf helper.

(In reply to Yvugenfi from comment #5)
> 
> Hi Michal,
> 
> This is just a basic support. Still some work is going on upstream to enable
> the usage with libvirt when QEMU runs without root privileges by using ebpf
> helper.

Hi Yan, downstream qemu do not enable the ebpf support, do we have the plan to enable it?

(In reply to Yvugenfi from comment #5)
> 

Alright then. Let me move this back to ASSIGNED so that the rest of the feature can be picked up by this bug later on.

(In reply to yalzhang from comment #6)
> (In reply to Yvugenfi from comment #5)
> > 
> > Hi Michal,
> > 
> > This is just a basic support. Still some work is going on upstream to enable
> > the usage with libvirt when QEMU runs without root privileges by using ebpf
> > helper.
> 
> Hi Yan, downstream qemu do not enable the ebpf support, do we have the plan
> to enable it?

In general yes. But we need to have a helper support in libvirt for this.

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