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

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Message-ID: <20230628050019.GC23952@unreal>
Date:   Wed, 28 Jun 2023 08:00:19 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Junxian Huang <huangjunxian6@...ilicon.com>
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 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

> > 
> > 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
> >>