netdev - Re: Oops in during sriov_enable with ixgbe driver

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Message-ID: <CAJZ5v0gpxRDt0V3Eh1_edZAudxyL3-ik4MhT7TzijTYeOd=_Vg@mail.gmail.com>
Date:   Thu, 30 Sep 2021 20:20:08 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Jesse Brandeburg <jesse.brandeburg@...el.com>
Cc:     Niklas Schnelle <schnelle@...ux.ibm.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: Oops in during sriov_enable with ixgbe driver

On Thu, Sep 30, 2021 at 7:38 PM Rafael J. Wysocki
<rafael.j.wysocki@...el.com> wrote:
>
> On 9/30/2021 7:31 PM, Jesse Brandeburg wrote:
> > On 9/28/2021 4:56 AM, Niklas Schnelle wrote:
> >> Hi Jesse, Hi Tony,
> >>
> >> Since v5.15-rc1 I've been having problems with enabling SR-IOV VFs on
> >> my private workstation with an Intel 82599 NIC with the ixgbe driver. I
> >> haven't had time to bisect or look closer but since it still happens on
> >> v5.15-rc3 I wanted to at least check if you're aware of the problem as
> >> I couldn't find anything on the web.
> > We haven't heard anything of this problem.
> >
> >
> >> I get below Oops when trying "echo 2 > /sys/bus/pci/.../sriov_numvfs"
> >> and suspect that the earlier ACPI messages could have something to do
> >> with that, absolutely not an ACPI expert though. If there is a need I
> >> could do a bisect.
> > Hi Niklas, thanks for the report, I added the Intel Driver's list for
> > more exposure.
> >
> > I asked the developers working on that driver to take a look and they
> > tried to reproduce, and were unable to do so. This might be related to
> > your platform, which strongly suggests that the ACPI stuff may be related.
> >
> > We have tried to reproduce but everything works fine no call trace in
> > scenario with creating VF.
> >
> > This is good in that it doesn't seem to be a general failure, you may
> > want to file a kernel bugzilla (bugzilla.kernel.org) to track the issue,
> > and I hope that @Rafael might have some insight.
> >
> > This issue may be related to changes in acpi_pci_find_companion,
> > but as I say, we are not able to reproduce this.
> >
> > commit 59dc33252ee777e02332774fbdf3381b1d5d5f5d
> > Author: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > Date:   Tue Aug 24 16:43:55 2021 +0200
> >      PCI: VMD: ACPI: Make ACPI companion lookup work for VMD bus
>
> This change doesn't affect any devices beyond the ones on the VMD bus.

The only failing case I can see is when the device is on the VMD bus
and its bus pointer is NULL, so the dereference in
vmd_acpi_find_companion() crashes.

Can anything like that happen?

> > At this point maybe a bisect would be helpful, since this seems to be a
> > corner case that we used to handle but no longer do.