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From: Cornelia Huck <cohuck@redhat.com>
Subject: Re: [virtio-dev] Re: [Qemu-devel] [PATCH] qemu: Introduce
 VIRTIO_NET_F_STANDBY feature bit to virtio_net
Date: Tue, 26 Jun 2018 17:17:32 +0200
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Cc: "Samudrala, Sridhar" <sridhar.samudrala@intel.com>,
        Siwei Liu <loseweigh@gmail.com>,
        Alexander Duyck <alexander.h.duyck@intel.com>,
        virtio-dev@lists.oasis-open.org, aaron.f.brown@intel.com,
        Jiri Pirko <jiri@resnulli.us>, Jakub Kicinski <kubakici@wp.pl>,
        Netdev <netdev@vger.kernel.org>, qemu-devel@nongnu.org,
        virtualization@lists.linux-foundation.org, konrad.wilk@oracle.com,
        boris.ostrovsky@oracle.com,
        Joao Martins <joao.m.martins@oracle.com>,
        Venu Busireddy <venu.busireddy@oracle.com>,
        vijay.balakrishna@oracle.com
To: "Michael S. Tsirkin" <mst@redhat.com>
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On Tue, 26 Jun 2018 04:50:25 +0300
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Mon, Jun 25, 2018 at 10:54:09AM -0700, Samudrala, Sridhar wrote:
> > > > > > Might not neccessarily be something wrong, but it's very limited to
> > > > > > prohibit the MAC of VF from changing when enslaved by failover.  
> > > > > You mean guest changing MAC? I'm not sure why we prohibit that.  
> > > > I think Sridhar and Jiri might be better person to answer it. My
> > > > impression was that sync'ing the MAC address change between all 3
> > > > devices is challenging, as the failover driver uses MAC address to
> > > > match net_device internally.  
> > 
> > Yes. The MAC address is assigned by the hypervisor and it needs to manage the movement
> > of the MAC between the PF and VF.  Allowing the guest to change the MAC will require
> > synchronization between the hypervisor and the PF/VF drivers. Most of the VF drivers
> > don't allow changing guest MAC unless it is a trusted VF.  
> 
> OK but it's a policy thing. Maybe it's a trusted VF. Who knows?
> For example I can see host just
> failing VIRTIO_NET_CTRL_MAC_ADDR_SET if it wants to block it.
> I'm not sure why VIRTIO_NET_F_STANDBY has to block it in the guest.
> 

So, what I get from this is that QEMU needs to be able to control all
of standby, uuid, and mac to accommodate the different setups
(respectively have libvirt/management software set it up). Is the host
able to find out respectively define whether a VF is trusted?