linux-kernel - Re: [PATCH v2 for-next] RDMA/core: Get IB width and speed from netdev

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Message-ID: <53e8025d-803d-f6c5-b853-8352163d9a2e@hisilicon.com>
Date:   Wed, 5 Jul 2023 11:05:50 +0800
From:   Junxian Huang <huangjunxian6@...ilicon.com>
To:     Leon Romanovsky <leon@...nel.org>
CC:     <jgg@...dia.com>, <linux-rdma@...r.kernel.org>,
        <linuxarm@...wei.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 for-next] RDMA/core: Get IB width and speed from netdev



On 2023/6/28 13:00, Leon Romanovsky wrote:
> On Mon, Jun 19, 2023 at 02:20:54PM +0800, Junxian Huang wrote:
>>
>>
>> On 2023/6/12 1:46, Leon Romanovsky wrote:
>>> On Sat, Jun 03, 2023 at 02:38:33PM +0800, Junxian Huang wrote:
>>>> From: Haoyue Xu <xuhaoyue1@...ilicon.com>
>>>>
>>>> Previously, there was no way to query the number of lanes for a network
>>>> card, so the same netdev_speed would result in a fixed pair of width and
>>>> speed. As network card specifications become more diverse, such fixed
>>>> mode is no longer suitable, so a method is needed to obtain the correct
>>>> width and speed based on the number of lanes.
>>>
>>> I'm sorry but I didn't understand the problem statement. Can you please
>>> provide an example of configuration that will give different results 
>>> before this patch and after?
>>>
>>
>> I'll give examples with 20G and 200G netdevs respectively.
>>
>> 20G:
>> Before this patch, regardless of the actual number of lanes, the width and
>> speed displayed in ibv_devinfo would be always fixed:
>> 	active_width: 4X
>> 	active_speed: 5 Gbps
>> After this patch, there will be different combinations of width and speed
>> according to the number of lanes. For example, for a 20G netdev whose number
>> of lanes is 2, the width and speed displayed in ibv_devinfo will be:
>> 	active_width: 2X
>> 	active_speed: 10 Gbps
>>
>> 200G:
>> Before this patch, netdevs with netdev_speed more than 40G cannot get a right
>> width and speed in ibv_devinfo. Only the default result would be displayed:
>> 	active_width: 4X
>> 	active_speed: 25 Gbps
>> After this patch, taking an example with 4 lanes, the displayed results will be:
>> 	active_width: 4X
>> 	active_speed: 50 Gbps
>>
> 
> <...>
> 
>>>> +	cap_link_lanes_supported = netdev->ethtool_ops->cap_link_lanes_supported;
>>>>  	rtnl_unlock();
>>>>  
>>>>  	dev_put(netdev);
>>>>  
>>>>  	if (!rc && lksettings.base.speed != (u32)SPEED_UNKNOWN) {
>>>>  		netdev_speed = lksettings.base.speed;
>>>> +		if (cap_link_lanes_supported && lksettings.lanes) {
>>>
>>> According to the documentation cap_link_lanes_supported defines if
>>> number of lanes can be supplied by user and I would expect from
>>> __ethtool_get_link_ksettings() to get right numbers after it was
>>> changed.
> 
> No, I'm saying that cap_link_lanes_supported is variable which only says
> if number of lanes can be changed and __ethtool_get_link_ksettings()
> will return right number of lanes every time it is called without need
> to call to ib_get_width_and_speed() again.
> 
> Thanks
> 

These two functions have different purposes.

The number of lanes is indeed obtained from __ethtool_get_link_ksettings(),
and ib_get_width_and_speed() converts the number of lanes into ib_width and
ib_speed, which are the output of ib_get_eth_speed().

Junxian

>>>
>>> Thanks
>>>
>>
>> I'm sorry but I didn't quite understand. Do you mean the critical section of
>> rtnl_lock() here should be expanded to make sure getting the right number of
>> lanes?
>>
>> Junxian
>>
>>>> +			ib_get_width_and_speed(netdev_speed, lksettings.lanes,
>>>> +					       speed, width);
>>>> +			return 0;
>>>> +		}
>>>>  	} else {
>>>>  		netdev_speed = SPEED_1000;
>>>> -		pr_warn("%s speed is unknown, defaulting to %u\n", netdev->name,
>>>> -			netdev_speed);
>>>> +		if (rc)
>>>> +			pr_warn("%s speed is unknown, defaulting to %u\n",
>>>> +				netdev->name, netdev_speed);
>>>>  	}
>>>>  
>>>>  	if (netdev_speed <= SPEED_1000) {
>>>> diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
>>>> index 1e7774ac808f..7dc926ec7fee 100644
>>>> --- a/include/rdma/ib_verbs.h
>>>> +++ b/include/rdma/ib_verbs.h
>>>> @@ -552,6 +552,18 @@ static inline int ib_width_enum_to_int(enum ib_port_width width)
>>>>  	}
>>>>  }
>>>>  
>>>> +static inline int ib_int_to_ib_width(u32 lanes)
>>>> +{
>>>> +	switch (lanes) {
>>>> +	case 1: return IB_WIDTH_1X;
>>>> +	case 2: return IB_WIDTH_2X;
>>>> +	case 4: return IB_WIDTH_4X;
>>>> +	case 8: return IB_WIDTH_8X;
>>>> +	case 12: return IB_WIDTH_12X;
>>>> +	default: return IB_WIDTH_1X;
>>>> +	}
>>>> +}
>>>> +
>>>>  enum ib_port_speed {
>>>>  	IB_SPEED_SDR	= 1,
>>>>  	IB_SPEED_DDR	= 2,
>>>> @@ -563,6 +575,20 @@ enum ib_port_speed {
>>>>  	IB_SPEED_NDR	= 128,
>>>>  };
>>>>  
>>>> +static inline int ib_eth_to_ib_speed(u32 speed)
>>>> +{
>>>> +	switch (speed) {
>>>> +	case SPEED_2500: return IB_SPEED_SDR;
>>>> +	case SPEED_5000: return IB_SPEED_DDR;
>>>> +	case SPEED_10000: return IB_SPEED_FDR10;
>>>> +	case SPEED_14000: return IB_SPEED_FDR;
>>>> +	case SPEED_25000: return IB_SPEED_EDR;
>>>> +	case SPEED_50000: return IB_SPEED_HDR;
>>>> +	case SPEED_100000: return IB_SPEED_NDR;
>>>> +	default: return IB_SPEED_SDR;
>>>> +	}
>>>> +}
>>>> +
>>>>  enum ib_stat_flag {
>>>>  	IB_STAT_FLAG_OPTIONAL = 1 << 0,
>>>>  };
>>>> -- 
>>>> 2.30.0
>>>>