Re: [Bug 55421] igb VF can't work in KVM guest

Alex Williamson
2013-03-21T22:21:23Z

On Thu, 2013-03-21 at 22:03 +0000, Williams, Mitch A wrote:
> Thanks for the FYI, Alex. When we pushed this patch upstream, there
> was a corresponding patch to igbvf that was pushed at the same time.
> With this patch, the VFs detect the zero address and generate a random
> MAC address themselves. The reason for this change is to make the VFs
> play nicely with udev. The issue was originally raised by Stefan
> Assmann.
>
> With older drivers in the guest, this will cause the issue you noted.
> Distros should cherry-pick the corresponding VF patch.

I agree the random MAC doesn't play nicely with udev, although I have
found that my guest stops adding new persistent net rules after
eth680 ;) Arguably anyone using VFs for more than testing should
already be assigning a stable MAC address, but I don't really think a
guest driver update across every possible guest OS is all that
practical. At least that explains why igbvf in the host is unaffected
though. Should we expect a Code 10 (device cannot start) from the
Windows igbvf driver when it finds a zero'd MAC? Thanks,

Alex

> > -----Original Message-----
> > From: Alex Williamson [mailto:alex.williamson@redhat.com]
> > Sent: Thursday, March 21, 2013 2:32 PM
> > To: Williams, Mitch A
> > Cc: kvm@vger.kernel.org
> > Subject: Re: [Bug 55421] igb VF can't work in KVM guest
> >
> > Mitch,
> >
> > Bugzilla wouldn't let me add you to the CC, so FYI...
> > Thanks,
> >
> > Alex
> >
> > On Thu, 2013-03-21 at 21:29 +0000, bugzilla-daemon@bugzilla.kernel.org
> > wrote:
> > > https://bugzilla.kernel.org/show_bug.cgi?id=55421
> > >
> > >
> > > Alex Williamson <alex.williamson@redhat.com> changed:
> > >
> > > What |Removed |Added
> > > --------------------------------------------------------------------------
> > --
> > > CC|
> > |alex.williamson@redhat.com,
> > > |
> > |jeffrey.t.kirsher@intel.com
> > >
> > >
> > >
> > >
> > > --- Comment #4 from Alex Williamson <alex.williamson@redhat.com> 2013-03-
> > 21 21:29:09 ---
> > > Further bisected to:
> > >
> > > commit 5ac6f91d39e0884813dc010e14552143cd1d0d8b
> > > Author: Mitch A Williams <mitch.a.williams@intel.com>
> > > Date: Fri Jan 18 08:57:20 2013 +0000
> > >
> > > igb: Don't give VFs random MAC addresses
> > >
> > > If the user has not assigned a MAC address to a VM, then don't give it
> > a
> > > random one. Instead, just give it zeros and let it figure out what to
> > do
> > > with them.
> > >
> > > Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
> > > CC: Andy Gospodarek <andy@greyhouse.net>
> > > CC: Stefan Assmann <sassmann@kpanic.de>
> > > Tested-by: Aaron Brown <aaron.f.brown@intel.com>
> > > Tested-by: Stefan Assmann <sassmann@redhat.com>
> > > Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> > >
> > > So, for whatever reason we no longer assign a random MAC address when
> > using the
> > > device in a VM (but we do still use one if attached to igbvf in the host).
> > I
> > > expect we'll eventually see this on all the Intel SR-IOV NICs. The
> > solution is
> > > to use the ip command to assign the VF a valid MAC address prior to using
> > it
> > > with KVM. I'll let those who made the change defend it further if they
> > wish.
> > >
> >