RE: New commands to configure IOV features

-----Original Message-----
From: Stephen Hemminger [mailto:shemminger@vyatta.com]
Sent: Monday, July 23, 2012 11:36 AM
To: Chris Friesen
Cc: Don Dutile; Ben Hutchings; David Miller; yuvalmin@broadcom.com; Rose,
Gregory V; netdev@vger.kernel.org; linux-pci@vger.kernel.org
Subject: Re: New commands to configure IOV features

On Mon, 23 Jul 2012 09:09:38 -0600
Chris Friesen [off-list ref] wrote:

quoted

On 07/23/2012 08:03 AM, Don Dutile wrote:

quoted

On 07/20/2012 07:42 PM, Chris Friesen wrote:

quoted

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?

quoted

quoted

quoted

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