Re: [libvirt] [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net

On 6/6/2018 11:52 AM, Ján Tomko wrote:

On Wed, Jun 06, 2018 at 11:17:36AM -0700, Samudrala, Sridhar wrote:

quoted

On 6/4/2018 7:06 PM, Jason Wang wrote:

quoted

On 2018年06月05日 09:41, Samudrala, Sridhar wrote:

quoted

Ping on this patch now that the kernel patches are accepted into
davem's net-next tree.
https://patchwork.ozlabs.org/cover/920005/


On 5/7/2018 4:09 PM, Sridhar Samudrala wrote:

quoted

This feature bit can be used by hypervisor to indicate virtio_net
device to
act as a standby for another device with the same MAC address.

I tested this with a small change to the patch to mark the STANDBY
feature 'true'
by default as i am using libvirt to start the VMs.
Is there a way to pass the newly added feature bit 'standby' to qemu
via libvirt
XML file?

Maybe you can try qemu command line passthrough:

https://libvirt.org/drvqemu.html#qemucommand

It looks like this can be used to pass command line arguments to qemu.
Is it possible to specify a virtio specific attribute via this method?

Yes, for testing purposes you should be able to do this via using QEMU's
-set command line argument:
http://blog.vmsplice.net/2011/04/how-to-pass-qemu-command-line-options.html 

i.e.:

<domain type='kvm' 
xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
 ...
 <qemu:commandline>
   <qemu:arg value='-set'/>
   <qemu:arg value='device.net0.standby=on'/>
 </qemu:commandline>
</domain>

Thanks. Will try this.

quoted

For ex: to say mrg_rxbuf is off we can add the following line to virtio
section of the domain xml file.
  <host mrg_rxbuf='off'/>

I think libvirt needs to be extended to to support the new 'standby' 
attribute
via this mechanism.
Adding Liane Stump and libvirt to the CC list.

*Laine

quoted

Michael,
Can we start with getting this patch into Qemu and an update to 
libvirt to
support the 'standby' feature so that this feature can be enabled via
some scripts/orchestration layer for now.

We could improve this solution by enhancing Qemu to do automatic 
management of the
addition/deletion of the primary device based on feature negotiation 
as a later patch.

If that means the libvirt attribute would no longer be needed, I don't
see the reason to add it to libvirt in the first place.

I think we still need this attribute supported via libvirt so that a user/admin
can enable this feature via domain XML specification.


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