Re: [dpdk-dev] [PATCH v5 0/9] ethdev: support SubFunction representor

["Xueming(Steven) Li" <xuemingl@nvidia.com>]

>-----Original Message-----
>From: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
>Sent: Friday, February 5, 2021 3:35 PM
>To: Xueming(Steven) Li <xuemingl@nvidia.com>
>Cc: dev@dpdk.org; Slava Ovsiienko <viacheslavo@nvidia.com>; Asaf Penso <asafp@nvidia.com>; Thomas Monjalon
><tmonjalon@nvidia.com>
>Subject: Re: [dpdk-dev] [PATCH v5 0/9] ethdev: support SubFunction representor
>
>On 2/4/21 5:15 PM, Xueming(Steven) Li wrote:
>>
>>> -----Original Message-----
>>> From: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
>>> Sent: Monday, February 1, 2021 4:39 PM
>>> To: Xueming(Steven) Li <xuemingl@nvidia.com>
>>> Cc: dev@dpdk.org; Slava Ovsiienko <viacheslavo@nvidia.com>; Asaf
>>> Penso <asafp@nvidia.com>
>>> Subject: Re: [dpdk-dev] [PATCH v5 0/9] ethdev: support SubFunction
>>> representor
>>>
>>> On 1/28/21 5:31 PM, Xueming(Steven) Li wrote:
>>>> <snip>
>>>>>> The patch of device SF capability, but seems I misunderstood your suggestion.
>>>>>> Let me explain process to create a SF:
>>>>>> 1. SF can be created on the fly with scripts, unlike VF which is statically pre-created.
>>>>>
>>>>> Is there a maximum index and maximum total number of SF's created? How to find it?
>>>>
>>>> The maximum index is defined by firmware configuration, all SF's
>>>> information could be found from sysfs. To create a SF, both PCI and sfnum have to be specified.
>>>
>>> sysfs is obviously Linux specific. I think the information should be available via DPDK API.
>>
>> Yes, the new api discussed below should resolve this issue.
>>
>>>
>>>>>
>>>>>> 2. SF is created on a PF with a SF number. SF number is named per PF, different PF may have same SF number.
>>>>>> 3. For standalone PF, hot plug to DPDK using "PF#_BDF,representor=sf#", no need to use pf#sf# here.
>>>>>> 4. For bonding netdev, hot plug to DPDK using "PF0_BDF,representor=pf#sf#"
>>>>>> If using new api to return all representor IDs, need some way
>>>>>> locate the new created SF by PF and SF number, that's why "pf#sf#" is used in this patch set.
>>>>>
>>>>> I think the API should simply reserve/report space for maximum
>>>>> number of SFs. So, IDs are stable across restart/reboot in
>>>>> assumption that NIC is not reconfigured (changed maximum number of
>>>>> VF or
>>> maximum number of SFs of any PF).
>>>>
>>>> Yes, IDs should be stable as long as no  NIC firmware configuration change.
>>>>
>>>> Just clarify, this api should be common enough to report all devices that a bus device supports:
>>>> 1. name, might contains controller and pf info, example: "eth:representor:c0pf1vf"
>>>> 2. ID range, example: 0-127
>>>> The api describes ID ranges for each sub device type, users have to query the api and choose representor ID to probe.
>>>>
>>>> Prototype:
>>>> struct rte_bus_device_range {
>>>> 	char name[64];
>>>> 	uint32_t base;
>>>> 	uint32_t number;
>>>> }
>>>> /* return number of ranges filled, or number of ranges if list is
>>>> NULL. */ int rte_bus_ dev_range_get(struct rte_bus_device_range
>>>> *list, int n);
>>>
>>> Hm, I thought about more port representor specific API.
>>> For me it is hard to tell if such generic naming is good or bad. I
>>> think it should be proven that such generic API makes sense. Any other potential users / use cases?
>>
>> I was thinking about SF, but SF is PCI specific, not suitable for this api. So I'm fine to make it as ethdev api.
>> To append new api into eth_dev_ops, is there ABI concern?
>
>No, eth_dev_ops are internal
>
>>> I've considered ethdev API which returns (in similar way as
>>> above) list of possible port representors which could be controlled
>>> by the device. Also I think it would be useful to include type information (enum with PF, VF, SF), controller ID.
>>
>> Agree.
>>
>> There is a new concern from orchestration side, currently, no
>> interface in openstack and OVS to retrieve representor ID range info,
>> It will take time to adapt this solution. To probe a representor,
>> orchestration need to know how to calculate representor ID, and the ID might vary on different max SF number, i.e. VF4 on PP1
>might got different ID. Representor ID change before that will break the product.
>
>I see.
>
>> Considering both orchestration and testpmd users, how about keeping both solution together? This will bring max flexibility IMHO.
>
>As I said before I don't mind and I really think it is a good idea to add suggested interface to specify representor (i.e. cXpfYvfZ), but the
>problem is making bitmap from representor ID.
>
>ethdev API should use new representor info API to make a representor ID from controller/PF/{VF,SF}.
>Or do you see any problems with such approach?

Sorry I thought the user to figure out representor ID from api.
This combination look good, thanks for clarification :)

So the new api looks like this:
struct rte_eth_representor_info {
  Enum representor_type;
  Uint16_t controller; // -1 for any
  Uint16_t port; // -1 for any
  Uint16_t representor_id;
  Uint16_t count;
  char name[N];

int rte_eth_representor_info_get(struct rte_eth_representor_info *infos);
- Return number of entries.
- NULL infos just return number of entries supported.
Sample outputs:
 VF, -1, 0, 0, 		128, 	"pf0vf"
 SF, -1, 0, 128, 		2048, 	"pf0sf"
 PF, -1, 0, 32767, 	1, 	"pf"
 VF, -1, 1, 32768, 	128, 	"pf1vf"
 SF, -1, 0, (32768+128), 	2048, 	"pf1sf"
 PF, -1, 0, 65535, 	1,	 "pf"

>
>> In struct rte_eth_dev_data, reserved bits could be used to define controller and port, this will avoid bitmap. How do you think?
>
>Could you add a bit more on it? Just a bit more details to the idea since I don't understand what exactly you mean and how it could
>help.

The idea is replacing reserved_64s and adding more device location info in rte_eth-dev_data like this:
  Uint16_t representor_id;
  Uint16_t port_id;
  Uint16_t controller_id;
  Enum representor_type;
Compare them all when matching a device, this will also avoid bitmap encoding. 
Reserved_64s[] was added to mitigate ABI conflicts, IIRC.
But seems no need if making representor info API to make ID.

>
>>>
>>> There is one more bit which is not in the picture yet -
>>> switch_info.port_id. Should it be equal to representor ID? Or different and provided in the info structure?
>>
>> Not exactly same AFAIK, the id used in e-switch.
>>
>>