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

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

Hi lads,

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Iremonger, Bernard
> Sent: Tuesday, September 27, 2016 3:13 PM
> To: Richardson, Bruce <bruce.richardson@intel.com>
> Cc: Thomas Monjalon <thomas.monjalon@6wind.com>; dev@dpdk.org; Jerin Jacob <jerin.jacob@caviumnetworks.com>; Shah, Rahul
> R <rahul.r.shah@intel.com>; Lu, Wenzhuo <wenzhuo.lu@intel.com>; azelezniak <alexz@att.com>
> Subject: Re: [dpdk-dev] [RFC PATCH v2 3/5] librte_ether: add API's for VF management
> 
> Hi Bruce,
> 
> <snip>
> 
> > > > > > Subject: Re: [dpdk-dev] [RFC PATCH v2 3/5] librte_ether: add
> > > > > > API's for VF management
> > > > > >
> > > > > > 2016-09-23 17:02, Iremonger, Bernard:
> > > > > > > From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> > > > > > > > 2016-09-23 09:53, Richardson, Bruce:
> > > > > > > > > From: Thomas Monjalon [mailto:thomas.monjalon@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?
> > > > > >
> > > > > > Not exactly. I'm thinking about a PMD specific API.
> > > > > > The only ethdev API you need would be a function to retrieve a
> > > > > > handler (an opaque pointer on the device struct) from the port id.
> > > > > > Then you can include rte_ixgbe.h and directly call the
> > > > > > specific ixgbe function, passing the device handler.
> > > > > > How does it sound?
> > > > >
> > > > > I have been prototyping this proposed solution, it appears to work.
> > > > >
> > > > > I have added the following function:
> > > > >
> > > > > int  rte_eth_dev_get_pmd_handle(uint8_t port_id, void**
> > > > > pmd_handle);
> > > > >
> > > > > The pmd_handle is a pointer to a dev_ops structure containing
> > > > > driver
> > > > specific functions.
> > > > >
> > > > > Using the pmd_handle the driver specific functions can be called
> > > > > (without having them in struct eth_dev_ops)
> > > > >
> > > > > Has this proposal been superseded by the discussion on the
> > > > > following
> > > > patch?
> > > > >
> > > > > [PATCH] net/vhost: Add function to retreive the 'vid' for a
> > > > > given port id
> > > >
> > > > Maybe, it can be superseded by this discussion, yes.
> > > > Bruce thinks we do not need rte_eth_dev_get_pmd_handle().
> > > > What is your opinion about using port_id directly and retrieving
> > > > the structs from the driver via rte_eth_devices?
> > >
> > > Looking at the code in rte_eth_devices[]
> > >
> > > struct rte_eth_dev  rte_eth_devices[RTE_MAX_ETHPORTS];
> > >
> > > struct rte_eth_dev {
> > >
> > > ...
> > >
> > > const struct eth_dev_ops *dev_ops; /**< Functions exported by PMD */
> > >
> > > ...
> > >
> > >  void *pmd_ops;  /** < exported PMD specific functions */
> > >
> > > }
> > >
> > > The PMD functions are only accessible at present if they are in
> > > struct
> > eth_dev_ops.
> > >
> > > Adding a pmd_ops field to struct rte_eth_dev {} makes the PMD
> > > functions
> > accessible and is a simpler solution than using
> > rte_eth_dev_get_pmd_handle() to get access to the PMD functions.
> > >
> > > Regards,
> > >
> >
> > Why would an ops structure be needed? If it's a private API for a
> > driver, there should be no need for function pointers, and instead the
> > driver can define regular functions in it's header file, no?
> >
> > /Bruce
> 
> The driver functions were static, I have made them public and added them to the rte_pmd_ixgbe.h file, and it works.  These functions
> will also need to be added to the rte_pmd_ixgbe_version.map file, previously there were no public functions.

Sorry for being late in the discussion, but I have a question:
If we  this way (force user to include driver specific headers and call driver specific functions),
how you guys plan to make this functionality available for multiple driver types.
>From discussion with Bernard  understand that customers would need similar functionality for i40e.
Does it mean that they'll have to re-implement this part of their code again?
Or would have to create (and maintain) their own shim layer that would provide some s of abstraction?
Basically their own version of rte_ethdev?

Konstantin

> 
> Regards,
> 
> Bernard.