linux-kernel - Re: PROBLEM: 4.15.0-rc3 APIC causes lockups on Core 2 Duo laptop

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Message-ID: <20171229001519.GD19819@bhelgaas-glaptop.roam.corp.google.com>
Date:   Thu, 28 Dec 2017 18:15:19 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Alexandru Chirvasitu <achirvasub@...il.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Dou Liyang <douly.fnst@...fujitsu.com>,
        Pavel Machek <pavel@....cz>,
        kernel list <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        "Maciej W. Rozycki" <macro@...ux-mips.org>,
        Mikael Pettersson <mikpelinux@...il.com>,
        Josh Poulson <jopoulso@...rosoft.com>,
        Mihai Costache <v-micos@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Marc Zyngier <marc.zyngier@....com>, linux-pci@...r.kernel.org,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Simon Xiao <sixiao@...rosoft.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Jork Loeser <Jork.Loeser@...rosoft.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        devel@...uxdriverproject.org, KY Srinivasan <kys@...rosoft.com>
Subject: Re: PROBLEM: 4.15.0-rc3 APIC causes lockups on Core 2 Duo laptop

On Thu, Dec 28, 2017 at 06:30:58PM -0500, Alexandru Chirvasitu wrote:
> Attached, but heads up on this: when redirecting the output of lspci
> -vvv to a text file as root I get
> 
> pcilib: sysfs_read_vpd: read failed: Input/output error
> 
> I can find bugs filed for various distros to this same effect, but
> haven't tracked down any explanations.

This is a tangent, but I think you should *always* see "Input/output
error" on this system when running "lspci -vvv" as root, regardless of
whether you redirect the output (the error probably goes to stderr,
not stdout, so it's probably easy to miss when not redirecting the
output).

I think this is the -EIO return from pci_vpd_read(), which probably
means pci_vpd_size() returned 0 for one of your devices, which means
the VPD data provided by the device wasn't formatted correctly.  If
this happens, you should see a warning in dmesg about it ("invalid VPD
tag" or similar) -- could you verify that?

It's possible we should return something other than -EIO, or maybe
pcilib should do something other than emitting the warning.  In
pcilib, sysfs_read_vpd() emits the warning [1], and it would seem sort
of ugly to special-case EIO, so maybe we should change this in the
kernel.

It looks like your Qualcomm Atheros Attansic NIC at 06:00.0 is the
only device with VPD, so that's probably the one:

  06:00.0 Ethernet controller: Qualcomm Atheros Attansic L2 Fast Ethernet
    Capabilities: [6c] Vital Product Data
      Not readable

I think lspci would still print "Not readable" if we just made the
kernel return 0 instead of -EIO [2].

Bjorn

[1] https://git.kernel.org/pub/scm/utils/pciutils/pciutils.git/tree/lib/sysfs.c#n410
[2] https://git.kernel.org/pub/scm/utils/pciutils/pciutils.git/tree/ls-vpd.c#n87