[dpdk-dev] [RFC PATCH v2 3/5] librte_ether: add API's for VF management

Iremonger, Bernard bernard.iremonger at intel.com
Fri Sep 23 19:02:16 CEST 2016


Hi Thoms

> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas.monjalon at 6wind.com]
> Sent: Friday, September 23, 2016 2:15 PM
> To: Richardson, Bruce <bruce.richardson at intel.com>; Iremonger, Bernard
> <bernard.iremonger at intel.com>
> Cc: dev at dpdk.org; Jerin Jacob <jerin.jacob at caviumnetworks.com>; Shah,
> Rahul R <rahul.r.shah at intel.com>; Lu, Wenzhuo <wenzhuo.lu at intel.com>;
> azelezniak <alexz at att.com>
> Subject: Re: [dpdk-dev] [RFC PATCH v2 3/5] librte_ether: add API's for VF
> management
> 
> 2016-09-23 09:53, Richardson, Bruce:
> > From: Thomas Monjalon [mailto:thomas.monjalon at 6wind.com]
> > > 2016-09-23 10:20, Bruce Richardson:
> > > > On Thu, Sep 22, 2016 at 07:04:37PM +0200, Thomas Monjalon wrote:
> > > > > 2016-09-15 16:46, Iremonger, Bernard:
> > > > > > > > > Do we really need to expose VF specific functions here?
> > > > > > > > > It can be generic(PF/VF) function indexed only through
> > > port_id.
> > > > > > > > > (example: as rte_eth_dev_set_vlan_anti_spoof(uint8_t
> > > > > > > > > port_id, uint8_t on)) For instance, In Thunderx PMD, We
> > > > > > > > > are not exposing a separate port_id for PF. We only
> > > > > > > > > enumerate 0..N VFs as 0..N ethdev port_id
> > > > > > > >
> > > > > > > > Our intention with this patch is to control the VF from the PF.
> > > > > > > >
> > > > > > > > The following librte_ether functions already work in a
> > > > > > > > similar
> > > way:
> > > > > > > >
> > > > > > > > rte_eth_dev_set_vf_rxmode(uint8_t port_id,  uint16_t vf,
> > > > > > > > uint16_t rx_mode, uint8_t on)
> > > > > > > >
> > > > > > > > rte_eth_dev_set_vf_rx(uint8_t port_id, uint16_t vf,
> > > > > > > > uint8_t
> > > > > > > > on)
> > > > > > > >
> > > > > > > > rte_eth_dev_set_vf_tx(uint8_t port_id, uint16_t vf,
> > > > > > > > uint8_t
> > > > > > > > on)
> > > > > > > >
> > > > > > > > int rte_eth_set_vf_rate_limit(uint8_t port_id, uint16_t
> > > > > > > > vf, uint16_t tx_rate, uint64_t q_msk)
> > > > > > >
> > > > > > > I have a bad feeling with these functions dedicated to VF from PF.
> > > > > > > Are we sure there is no other way?
> > > > > > > I mean we just need to know the VF with a port ID.
> > > > > >
> > > > > > When the VF is used in a VM the port ID of the VF is not
> > > > > > visible to
> > > the PF.
> > > > > > I don't think there is another way to do this.
> > > > >
> > > > > I don't understand why we could not assign a port id to the VF
> > > > > from the host instead of having the couple PF port id / VF id.
> > > > > Can we enumerate all the VFs associated to a PF?
> > > > > Then can we allocate them a port id in the array rte_eth_devices?
> > > >
> > > > Hi Thomas,
> > > >
> > > > The VF is not a port visible to DPDK, though, so it shouldn't have
> > > > a port id IMHO. DPDK can't actually do anything with it.
> > >
> > > You say the contrary below.
> >
> > Well, yes and no. The driver can manipulate things for the VF, but DPDK
> doesn't actually have a device that corresponds to the VF. There are no PCI
> bar mappings for it, DPDK can't do RX and TX with it etc.?
> 
> Very good point.
> There are only few ethdev functions which are supported by every drivers,
> like Rx/Tx and would not be available for VF from PF interface.
> 
> > > > The PCI device for the VF is likely passed through to a different
> > > > VM and being used there. Unfortunately, the VF still needs certain
> > > > things done for it by the PF, so if the PF is under DPDK control,
> > > > it needs to provide the functionality to assist the VF.
> > >
> > > Why not have a VF_from_PF driver which does the mailbox things?
> > > So you can manage the VF from the PF with a simple port id.
> > > It really seems to be the cleanest design to me.
> >
> > While I see your point, and it could work, I just want to be sure that we are
> ok with the results of that. Suppose we do create ethdevs for the VFs
> controlled by the PF. Does the new VF get counted in the
> rte_eth_dev_count() value (I assume yes)? How are apps meant to use the
> port? Do they have to put in a special case when iterating through all the port
> ids to check that it's not a pseudo port that can't do anything. None of the
> standard ethdev calls from an app will work on it, you can't configure nb rx/tx
> queues on it, you can't start or stop it, you can't do rx or tx on it, etc, etc.
> 
> Yes these devices would be special because their supported API would be
> quite different. I was thinking that in the future you could add most of the
> configuration functions through the VF mailbox.
> But the Intel mailbox currently support only some special configurations
> which are not supported by other devices even its own VF device (except
> setting MAC address).
> And when I read "set drop enable bit in the VF split rx control register", it
> becomes clear it is really specific and has nothing to do in the generic ethdev
> API.
> That's why it is a NACK.
> 
> When we want to use these very specific features we are aware of the
> underlying device and driver. So we can directly include a header from the
> driver. I suggest to retrieve a handler for the device which is not a port id and
> will allow to call ixgbe functions directly.
> It could be achieved by adding an ethdev function like discussed here:
> 	http://dpdk.org/ml/archives/dev/2016-September/047392.html
> 

I have been reading the net/vhost mail thread above. The following quote is from this thread.

"It means I would be in favor of introducing API in drivers for very specific features."

At present all the PMD functions are accessed through the eth_dev_ops structure, there are no PMD API's.

Is your proposal to add API(s) to the DPDK ixgbe PMD (similar to a driver ioctl API) which can be accessed through a generic API in the ethdev?

What will this generic API look like?

Regards,

Bernard.




More information about the dev mailing list