From: Bjorn Helgaas <helgaas@kernel.org>
To: Paul Menzel <pmenzel+linux-pci@molgen.mpg.de>
Cc: okaya@codeaurora.org, Bjorn Helgaas <bhelgaas@google.com>,
linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
Lukas Wunner <lukas@wunner.de>
Subject: Re: pciehp 0000:00:1c.0:pcie004: Timeout on hotplug command 0x1038 (issued 65284 msec ago)
Date: Tue, 8 May 2018 07:34:32 -0500 [thread overview]
Message-ID: <20180508123432.GJ161390@bhelgaas-glaptop.roam.corp.google.com> (raw)
In-Reply-To: <903e7c20-fdd7-9cbf-debb-a90e70240c7c@molgen.mpg.de>
On Tue, May 08, 2018 at 08:59:34AM +0200, Paul Menzel wrote:
> Dear Bjorn,
>
>
> Am 07.05.2018 um 23:33 schrieb Bjorn Helgaas:
> > On Fri, May 04, 2018 at 08:33:27AM -0500, Bjorn Helgaas wrote:
> > > commit b0d6f2230e12c85ae3b65a854a53c67c7c1f6406
> > > Author: Bjorn Helgaas <bhelgaas@google.com>
> > > Date: Thu May 3 18:39:38 2018 -0500
> > >
> > > PCI: pciehp: Add quirk for Intel Command Completed erratum
> > > The Intel CF118 erratum means the controller does not set the Command
> > > Completed bit unless writes to the Slot Command register change "Control"
> > > bits. Command Completed is never set for writes that only change software
> > > notification "Enable" bits. This results in timeouts like this:
> > > pciehp 0000:00:1c.0:pcie004: Timeout on hotplug command 0x1038 (issued 65284 msec ago)
> > > When this erratum is present, avoid these timeouts by marking commands
> > > "completed" immediately unless they change the "Control" bits.
> > > Here's the text of the erratum from the Intel document:
> > > CF118 PCIe Slot Status Register Command Completed bit not always
> > > updated on any configuration write to the Slot Control
> > > Register
> > > Problem: For PCIe root ports (devices 0 - 10) supporting hot-plug,
> > > the Slot Status Register (offset AAh) Command Completed
> > > (bit[4]) status is updated under the following condition:
> > > IOH will set Command Completed bit after delivering the new
> > > commands written in the Slot Controller register (offset
> > > A8h) to VPP. The IOH detects new commands written in Slot
> > > Control register by checking the change of value for Power
> > > Controller Control (bit[10]), Power Indicator Control
> > > (bits[9:8]), Attention Indicator Control (bits[7:6]), or
> > > Electromechanical Interlock Control (bit[11]) fields. Any
> > > other configuration writes to the Slot Control register
> > > without changing the values of these fields will not cause
> > > Command Completed bit to be set.
> > > The PCIe Base Specification Revision 2.0 or later describes
> > > the “Slot Control Register” in section 7.8.10, as follows
> > > (Reference section 7.8.10, Slot Control Register, Offset
> > > 18h). In hot-plug capable Downstream Ports, a write to the
> > > Slot Control register must cause a hot-plug command to be
> > > generated (see Section 6.7.3.2 for details on hot-plug
> > > commands). A write to the Slot Control register in a
> > > Downstream Port that is not hotplug capable must not cause a
> > > hot-plug command to be executed.
> > > The PCIe Spec intended that every write to the Slot Control
> > > Register is a command and expected a command complete status
> > > to abstract the VPP implementation specific nuances from the
> > > OS software. IOH PCIe Slot Control Register implementation
> > > is not fully conforming to the PCIe Specification in this
> > > respect.
> > > Implication: Software checking on the Command Completed status after
> > > writing to the Slot Control register may time out.
> > > Workaround: Software can read the Slot Control register and compare the
> > > existing and new values to determine if it should check the
> > > Command Completed status after writing to the Slot Control
> > > register.
> > > Link: http://www.intel.com/content/www/us/en/processors/xeon/xeon-e7-v2-spec-update.html
> > > Link: https://lkml.kernel.org/r/8770820b-85a0-172b-7230-3a44524e6c9f@molgen.mpg.de
> > > Reported-by: Paul Menzel <pmenzel+linux-pci@molgen.mpg.de>
> > > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> >
> > I applied this with Paul's tested-by on pci/hotplug for v4.18.
>
> Thank you very much. Will this also be picked up by the stable Linux kernel
> series?
I did not tag it for stable because I didn't think it was a serious enough
problem, based on this from Documentation/process/stable-kernel-rules.rst:
- It must fix a problem that causes a build error (but not for things
marked CONFIG_BROKEN), an oops, a hang, data corruption, a real
security issue, or some "oh, that's not good" issue. In short, something
critical.
I know I'm on the conservative end of the stable-tagging spectrum, so maybe
I could be convinced to add a stable tag.
My impression was that this bug caused annoying messages and annoying
delays of a couple seconds during shutdown and resume. Is it more serious
than that?
Bjorn
next prev parent reply other threads:[~2018-05-08 12:34 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-26 10:17 pciehp 0000:00:1c.0:pcie004: Timeout on hotplug command 0x1038 (issued 65284 msec ago) Paul Menzel
2018-04-27 19:22 ` Bjorn Helgaas
2018-04-27 19:34 ` Sinan Kaya
2018-04-27 21:12 ` Bjorn Helgaas
2018-04-28 0:56 ` Dave Young
2018-04-28 1:18 ` Dave Young
2018-04-28 13:03 ` okaya
2018-04-30 20:48 ` Sinan Kaya
2018-04-30 21:17 ` Bjorn Helgaas
2018-04-30 21:27 ` Sinan Kaya
2018-04-30 21:38 ` Lukas Wunner
2018-05-01 12:38 ` Sinan Kaya
2018-05-01 12:59 ` Marc Zyngier
2018-05-01 13:25 ` Bjorn Helgaas
2018-05-01 16:31 ` Marc Zyngier
2018-05-01 22:32 ` Eric W. Biederman
2018-05-03 8:49 ` Paul Menzel
2018-05-04 2:45 ` Bjorn Helgaas
2018-05-04 6:37 ` okaya
2018-05-04 13:33 ` Bjorn Helgaas
2018-05-04 14:24 ` okaya
2018-05-06 9:35 ` Paul Menzel
2018-05-07 21:33 ` Bjorn Helgaas
2018-05-08 6:59 ` Paul Menzel
2018-05-08 12:34 ` Bjorn Helgaas [this message]
2018-05-08 13:22 ` Paul Menzel
2018-05-09 11:41 ` Lukas Wunner
2018-05-09 12:57 ` Bjorn Helgaas
2018-05-09 13:16 ` Lukas Wunner
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