linux-kernel - Re: igb: do not re-init SR-IOV during probe

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Message-ID: <1444038386.27271.0@outlook-emeawest.office365.com>
Date:	Mon, 5 Oct 2015 17:46:26 +0800
From:	Daniel J Blueman <daniel@...ascale.com>
To:	<stable@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	Steffen Persvold <sp@...ascale.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Stefan Assmann <sassmann@...nic.de>,
	Aaron Brown <aaron.f.brown@...el.com>
Subject: Re: igb: do not re-init SR-IOV during probe

It would be great if the patch "igb: do not re-init SR-IOV during 
probe" [1] can be backported from 4.3-rc to stable kernels, since it 
fixes the regression introduced by "igb: do a reset on SR-IOV re-init 
if device is down" [2].

The regression was introduced in 3.16 and can isolate the IPMI 
interface on servers with 82576 NICs if using shared mode (high 
impact), around 0.5% of times booted.

Many thanks!
  Daniel

-- [1]

commit 6423fc34160939142d72ffeaa2db6408317f54df
Author: Stefan Assmann <sassmann@...nic.de>
Date:   Fri Jul 10 15:01:12 2015 +0200

    igb: do not re-init SR-IOV during probe

    During driver probing the following code path is triggered.
    igb_probe
    ->igb_sw_init
      ->igb_probe_vfs
        ->igb_pci_enable_sriov
          ->igb_sriov_reinit

    Doing the SR-IOV re-init is not necessary during probing since we're
    starting from scratch. Here we can call igb_enable_sriov() right 
away.

    Running igb_sriov_reinit() during igb_probe() also seems to cause
    occasional packet loss on some onboard 82576 NICs. Reproduced on
    Dell and HP servers with onboard 82576 NICs.
    Example:
    Intel Corporation 82576 Gigabit Network Connection [8086:10c9] (rev 
01)
    Subsystem: Dell Device [1028:0481]

    Signed-off-by: Stefan Assmann <sassmann@...nic.de>
    Tested-by: Aaron Brown <aaron.f.brown@...el.com>
    Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>

-- [2]

commit 76252723e88681628a3dbb9c09c963e095476f73
Author: Stefan Assmann <sassmann@...nic.de>
Date:   Thu Jul 10 03:29:39 2014 -0700

   igb: do a reset on SR-IOV re-init if device is down

   To properly re-initialize SR-IOV it is necessary to reset the device
   even if it is already down. Not doing this may result in Tx unit 
hangs.

   Cc: stable <stable@...r.kernel.org>
   Signed-off-by: Stefan Assmann <sassmann@...nic.de>
   Tested-by: Aaron Brown <aaron.f.brown@...el.com>
   Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
   Signed-off-by: David S. Miller <davem@...emloft.net>


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