netdev - Re: New commands to configure IOV features

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Date:	Mon, 23 Jul 2012 09:09:38 -0600
From:	Chris Friesen <chris.friesen@...band.com>
To:	Don Dutile <ddutile@...hat.com>
CC:	Ben Hutchings <bhutchings@...arflare.com>,
	David Miller <davem@...emloft.net>, yuvalmin@...adcom.com,
	gregory.v.rose@...el.com, netdev@...r.kernel.org,
	linux-pci@...r.kernel.org
Subject: Re: New commands to configure IOV features

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.

Chris

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