On Tue, Sep 27, 2016 at 11:31:06AM +0100, Iremonger, Bernard wrote:

Hi Thomas, Bruce,

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

2016-09-26 15:37, Iremonger, Bernard:

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Hi Thomas, Bruce,

<snip>

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

2016-09-23 17:02, Iremonger, Bernard:

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From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]

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2016-09-23 09:53, Richardson, Bruce:

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From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]

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2016-09-23 10:20, Bruce Richardson:

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On Thu, Sep 22, 2016 at 07:04:37PM +0200, Thomas Monjalon

wrote:

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2016-09-15 16:46, Iremonger, Bernard:

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Do we really need to expose VF specific functions

here?

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It can be generic(PF/VF) function indexed only
through

port_id.

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(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.

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The following librte_ether functions already work
in a similar

way:

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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.

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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.

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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.

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Can we enumerate all the VFs associated to a PF?
Then can we allocate them a port id in the array

rte_eth_devices?

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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.

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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.

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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.

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Why not have a VF_from_PF driver which does the mailbox

things?

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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.

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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.

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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.

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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.

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

features."

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At present all the PMD functions are accessed through the
eth_dev_ops

structure, there are no PMD API's.

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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.

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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?

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[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