linux-kernel - Re: [PATCH v2 net-next 3/3] octeontx2-af: Add devlink health reporters for NIX

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Date:   Fri, 06 Nov 2020 12:58:25 -0800
From:   Saeed Mahameed <saeed@...nel.org>
To:     Sunil Kovvuri <sunil.kovvuri@...il.com>
Cc:     George Cherian <gcherian@...vell.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jiri Pirko <jiri@...dia.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Sunil Kovvuri Goutham <sgoutham@...vell.com>,
        Linu Cherian <lcherian@...vell.com>,
        Geethasowjanya Akula <gakula@...vell.com>,
        "masahiroy@...nel.org" <masahiroy@...nel.org>,
        "willemdebruijn.kernel@...il.com" <willemdebruijn.kernel@...il.com>
Subject: Re: [PATCH v2 net-next 3/3] octeontx2-af: Add devlink health
 reporters for NIX

On Fri, 2020-11-06 at 00:59 +0530, Sunil Kovvuri wrote:
> > > > > Output:
> > > > >  # ./devlink health
> > > > >  pci/0002:01:00.0:
> > > > >    reporter npa
> > > > >      state healthy error 0 recover 0
> > > > >    reporter nix
> > > > >      state healthy error 0 recover 0
> > > > >  # ./devlink  health dump show pci/0002:01:00.0 reporter nix
> > > > >   NIX_AF_GENERAL:
> > > > >          Memory Fault on NIX_AQ_INST_S read: 0
> > > > >          Memory Fault on NIX_AQ_RES_S write: 0
> > > > >          AQ Doorbell error: 0
> > > > >          Rx on unmapped PF_FUNC: 0
> > > > >          Rx multicast replication error: 0
> > > > >          Memory fault on NIX_RX_MCE_S read: 0
> > > > >          Memory fault on multicast WQE read: 0
> > > > >          Memory fault on mirror WQE read: 0
> > > > >          Memory fault on mirror pkt write: 0
> > > > >          Memory fault on multicast pkt write: 0
> > > > >    NIX_AF_RAS:
> > > > >          Poisoned data on NIX_AQ_INST_S read: 0
> > > > >          Poisoned data on NIX_AQ_RES_S write: 0
> > > > >          Poisoned data on HW context read: 0
> > > > >          Poisoned data on packet read from mirror buffer: 0
> > > > >          Poisoned data on packet read from mcast buffer: 0
> > > > >          Poisoned data on WQE read from mirror buffer: 0
> > > > >          Poisoned data on WQE read from multicast buffer: 0
> > > > >          Poisoned data on NIX_RX_MCE_S read: 0
> > > > >    NIX_AF_RVU:
> > > > >          Unmap Slot Error: 0
> > > > > 
> > > > 
> > > > Now i am a little bit skeptic here, devlink health reporter
> > > > infrastructure was
> > > > never meant to deal with dump op only, the main purpose is to
> > > > diagnose/dump and recover.
> > > > 
> > > > especially in your use case where you only report counters, i
> > > > don't
> > > > believe
> > > > devlink health dump is a proper interface for this.
> > > These are not counters. These are error interrupts raised by HW
> > > blocks.
> > > The count is provided to understand on how frequently the errors
> > > are
> > > seen.
> > > Error recovery for some of the blocks happen internally. That is
> > > the
> > > reason,
> > > Currently only dump op is added.
> > 
> > So you are counting these events in driver, sounds like a counter
> > to
> > me, i really think this shouldn't belong to devlink, unless you
> > really
> > utilize devlink health ops for actual reporting and recovery.
> > 
> > what's wrong with just dumping these counters to ethtool ?
> 
> This driver is a administrative driver which handles all the
> resources
> in the system and doesn't do any IO.
> NIX and NPA are key co-processor blocks which this driver handles.
> With NIX and NPA, there are pieces
> which gets attached to a PCI device to make it a networking device.
> We
> have netdev drivers registered to this
> networking device. Some more information about the drivers is
> available at
> https://www.kernel.org/doc/html/latest/networking/device_drivers/ethernet/marvell/octeontx2.html
> 
> So we don't have a netdev here to report these co-processor block
> level errors over ethtool.
> 

but AF driver can't be standalone to operate your hw, it must have a
PF/VF with netdev interface to do io, so even if your model is modular,
a common user of this driver will always see a netdev.