netdev - RE: [(RFC) PATCH ] be2net: Allow a VF to use physical link state.

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Date:   Wed, 10 Jun 2020 10:22:22 -0700
From:   dwilder <dwilder@...ibm.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, wilder@...ibm.com,
        ajit.khaparde@...adcom.com, sriharsha.basavapatna@...adcom.com,
        somnath.kotur@...adcom.com
Subject: RE: [(RFC) PATCH ] be2net: Allow a VF to use physical link state.

On 2020-06-09 14:58, Jakub Kicinski wrote:
> On Mon,  8 Jun 2020 17:00:59 -0700 David Wilder wrote:
>> Hyper-visors owning a PF are allowed by Emulex specification to 
>> provide
>> a VF with separate physical and/or logical link states. However, on
>> linux, a VF driver must chose one or the other.
>> 
>> My scenario is a proprietary driver controlling the PF, be2net is the 
>> VF.
>> When I do a physical cable pull test the PF sends a link event
>> notification to the VF with the "physical" link status but this is
>> ignored in be2net (see be_async_link_state_process() ).
>> 
>> The PF is reporting the adapter type as:
>> 0xe228   /* Device id for VF in Lancer */
>> 
>> I added a module parameter "use_pf_link_state". When set the VF should
>> ignore logical link state and use the physical link state.
>> 
>> However I have an issue making this work.  When the cable is pulled I
>> see two link statuses reported:
>> [1706100.767718] be2net 8002:01:00.0 eth1: Link is Down
>> [1706101.189298] be2net 8002:01:00.0 eth1: Link is Up
>> 
>> be_link_status_update() is called twice, the first with the physical 
>> link
>> status called from be_async_link_state_process(), and the second with 
>> the
>> logical link status from be_get_link_ksettings().
>> 
>> I am unsure why be_async_link_state_process() is called from
>> be_get_link_ksettings(), it results in multiple link state changes
>> (even in the un-patched case). If I eliminate this call then it works.
>> But I am un-sure of this change.
>> 
>> Signed-off-by: David Wilder <dwilder@...ibm.com>
> 
> Hm. Just looking at the code in __be_cmd_set_logical_link_config():
> 
> 
> 	if (link_state == IFLA_VF_LINK_STATE_ENABLE ||
> 	    link_state == IFLA_VF_LINK_STATE_AUTO)
> 		link_config |= PLINK_ENABLE;
> 
> 	if (link_state == IFLA_VF_LINK_STATE_AUTO)
> 		link_config |= PLINK_TRACK;
> 
> Maybe we shouldn't set ENABLE for AUTO?

If I am understanding this correctly, this is used by the linux PF 
driver to configure
how link status is delivered to a VF.

My problem is one of interoperability between the PF (not linux) and the 
VF is running on linux.
The PF driver is implemented to the Emulex/Broadcom spec, which allows a 
PF driver to be configured such that the VF can be notified of both 
physical and logical link status, separately.

> 
> The module parameter is definitely not a good idea, what you're asking
> for seems to be well within the expectation from the
> .ndo_set_vf_link_state config, so it seems the driver / firmware is 
> just
> not implementing that right.

I am attempting to resolve an issue that the linux implementation cant 
conform to the the Emulex specification due to the implementation on 
linux.