Re: [dpdk-dev] SR-IOV: API to tell VF from PF

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Polehn, Mike A
> Sent: Thursday, November 05, 2015 5:59 PM
> To: Richardson, Bruce; Shaham Fridenberg
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] SR-IOV: API to tell VF from PF
> 
> A VF should support promiscuous mode, however this is different than a PF supporting promiscuous mode.
> 
> What happens to network throughput, which is tied to PCEe throughput, when say when 4 VFs are each in promiscuous mode. It
> should support it, but very negative effect.

In the usual model it is not up to VF/VM to decide what fraction of the total device resources it allowed to use.
It is responsibility of the PF/Hypervsior to devide total device bandwidths between VFs/VM, 
decide which VF will be a mirror if any, etc.
Konstantin

> 
> Not all NICs are created equal. The program should be able to quarry the device driver and be able to determine if it is the correct NIC
> type is being used. The device driver type should only match to the device type, which should be specific to VF or PF.


> 
> Mike
> 
> -----Original Message-----
> From: Richardson, Bruce
> Sent: Thursday, November 5, 2015 7:51 AM
> To: Polehn, Mike A; Shaham Fridenberg
> Cc: dev@dpdk.org
> Subject: RE: [dpdk-dev] SR-IOV: API to tell VF from PF
> 
> 
> 
> > -----Original Message-----
> > From: Polehn, Mike A
> > Sent: Thursday, November 5, 2015 3:43 PM
> > To: Richardson, Bruce <bruce.richardson@intel.com>; Shaham Fridenberg
> > <ShahamF@Radware.com>
> > Cc: dev@dpdk.org
> > Subject: RE: [dpdk-dev] SR-IOV: API to tell VF from PF
> >
> > I can think of a very good reason to want to know if the device is VF
> > or PF.
> >
> > The VF has to go through a layer 2 switch, not allowing it to just
> > receive anything coming across the Ehternet.
> >
> > The PF can receive all the packets, including packets with different
> > NIC addresses. This allow the packets to be just data and allows the
> > processing of data without needing to be adjusting each NIC L2 address
> > before sending through to the Ehternet. So data can be moved through a
> > series of NICs between systems without the extra processing. Not doing
> > unnecessary  processing leaves more clock cycles to do high value
> > processing.
> >
> > Mike
> >
> 
> Yes, the capabilities of the different types of devices are different.
> 
> However, is a better solution not to provide the ability to query a NIC if it supports promiscuous mode, rather than set up a specific
> query for a VF? What if (hypothetically) you get a PF that doesn't support promiscuous mode, for instance, or a bifurcated driver
> where the kernel part prevents the userspace part from enabling promiscuous mode? In both these cases have a direct feature query
> works better than asking about PF/VF.
> 
> Regards,
> 
> /Bruce
> 
> > -----Original Message-----
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Bruce Richardson
> > Sent: Thursday, November 5, 2015 1:51 AM
> > To: Shaham Fridenberg
> > Cc: dev@dpdk.org
> > Subject: Re: [dpdk-dev] SR-IOV: API to tell VF from PF
> >
> > On Thu, Nov 05, 2015 at 09:39:19AM +0000, Shaham Fridenberg wrote:
> > > Hey all,
> > >
> > > Is there some API to tell VF from PF?
> > >
> > > Only way I found so far is deducing that from driver name in the
> > rte_eth_devices struct.
> > >
> > > Thanks,
> > > Shaham
> >
> > Hi Shaham,
> >
> > yes, checking the driver name is probably the only way to do so.
> > However, why do you need or want to know this? If you want to know the
> > capabilities of a device basing it on a list of known device types is
> > probably not the best way.
> >
> > Regards,
> > /Bruce