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

On Wed, Jun 06, 2018 at 11:17:36AM -0700, Samudrala, Sridhar wrote: > On 6/4/2018 7:06 PM, Jason Wang wrote: >> >> >> On 2018年06月05日 09:41, Samudrala, Sridhar wrote: >>> 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: >>>> 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>

> 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 > > 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.