netdev - RE: New commands to configure IOV features

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Date:	Mon, 23 Jul 2012 18:40:51 +0000
From:	"Rose, Gregory V" <gregory.v.rose@...el.com>
To:	Stephen Hemminger <shemminger@...tta.com>,
	Chris Friesen <chris.friesen@...band.com>
CC:	Don Dutile <ddutile@...hat.com>,
	Ben Hutchings <bhutchings@...arflare.com>,
	David Miller <davem@...emloft.net>,
	"yuvalmin@...adcom.com" <yuvalmin@...adcom.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: RE: New commands to configure IOV features

> -----Original Message-----
> From: Stephen Hemminger [mailto:shemminger@...tta.com]
> Sent: Monday, July 23, 2012 11:36 AM
> To: Chris Friesen
> Cc: Don Dutile; Ben Hutchings; David Miller; yuvalmin@...adcom.com; Rose,
> Gregory V; netdev@...r.kernel.org; linux-pci@...r.kernel.org
> Subject: Re: New commands to configure IOV features
> 
> On Mon, 23 Jul 2012 09:09:38 -0600
> Chris Friesen <chris.friesen@...band.com> wrote:
> 
> > On 07/23/2012 08:03 AM, Don Dutile wrote:
> > > On 07/20/2012 07:42 PM, Chris Friesen wrote:
> > >>
> > >> I actually have a use-case where the guest needs to be able to
> > >> modify the MAC addresses of network devices that are actually VFs.
> > >>
> > >> The guest is bonding the network devices together, so the bonding
> > >> driver in the guest expects to be able to set all the slaves to the
> > >> same MAC address.
> > >>
> > >> As I read the ixgbe driver, this should be possible as long as the
> > >> host hasn't explicitly set the MAC address of the VF. Is that
> correct?
> > >>
> > >> Chris
> > >
> > > Interesting tug of war: hypervisors will want to set the macaddrs
> > > for security reasons,
> > >                         some guests may want to set macaddr for
> > > (valid?) config reasons.
> > >
> >
> > In our case we have control over both guest an host anyways, so it's
> > less of a security issue.  In the general case though I could see it
> > being an interesting problem.
> >
> > Back to the original discussion though--has anyone got any ideas about
> > the best way to trigger runtime creation of VFs?  I don't know what
> > the binary APIs looks like, but via sysfs I could see something like
> >
> > echo number_of_new_vfs_to_create >
> > /sys/bus/pci/devices/<address>/create_vfs
> >
> > Something else that occurred to me--is there buy-in from driver
> > maintainers?  I know the Intel ethernet drivers (what I'm most
> > familiar
> > with) would need to be substantially modified to support on-the-fly
> > addition of new vfs.  Currently they assume that the number of vfs is
> > known at module init time.
> >
> 
> Why couldn't rtnl_link_ops be used for this. It is already the preferred
> interface to create vlan's, bond devices, and other virtual devices?
> The one issue is that do the created VF's exist in kernel as devices or
> only visible to guest?

I would say that rtnl_link_ops are network oriented and not appropriate for something like a storage controller or graphics device, which are two other common SR-IOV capable devices.

I think it should be oriented toward the PCIe interface and subsystems in the kernel.

- Greg


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