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FreeBSD-EN-17:01.pcie                                           Errata Notice
                                                          The FreeBSD Project

Topic:          System hang when booting when PCI-express HotPlug is enabled

Category:       core
Module:         kernel
Announced:      2017-02-23
Credits:        Alan Somers, Dave Baukus
Affects:        FreeBSD 11.0
Corrected:      2017-02-07 22:40:38 UTC (stable/11, 11.0-STABLE)
                2017-02-23 07:11:48 UTC (releng/11.0, 11.0-RELEASE-p8)

For general information regarding FreeBSD Errata Notices and Security
Advisories, including descriptions of the fields above, security
branches, and the following sections, please visit
<URL:https://security.FreeBSD.org/>.

I.   Background

Native PCI-express HotPlug permits PCI-express devices to be added and
removed at runtime in slots that support HotPlug.

II.  Problem Description

Some PCI-express slots indicate partial support for PCI-express HotPlug
in the capability registers associated with an individual slot.  The
PCI-express HotPlug driver attempted to configure these slots for HotPlug
operation.  However, since these slots do not fully support HotPlug,
enabling HotPlug results in unpredictable behavior.

III. Impact

On at least some systems, booting a kernel with PCI-express HotPlug
support can hang.

IV.  Workaround

The hw.pci.enable_pcie_hp loader tunable can be set to 0 to disable
support for PCI-express HotPlug before booting an affected kernel.

V.   Solution

Perform one of the following:

1) Upgrade your system to a supported FreeBSD stable or release / security
branch (releng) dated after the correction date.

Afterward, reboot the system.

2) To update your system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

Afterward, reboot the system.

3) To update your system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch https://security.FreeBSD.org/patches/EN-17:01/pcie.patch
# fetch https://security.FreeBSD.org/patches/EN-17:01/pcie.patch.asc
# gpg --verify pcie.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel as described in
<URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/11/                                                        r313408
releng/11.0/                                                      r314125
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=211699>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-17:01.pcie.asc>
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