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FreeBSD-EN-23:10.pci                                            Errata Notice
                                                          The FreeBSD Project

Topic:          PCI-e hot-plug is broken with certain devices

Category:       core
Module:         pci
Announced:      2023-09-06
Affects:        FreeBSD 13.2
Corrected:      2023-06-28 01:32:47 UTC (stable/13, 13.2-STABLE)
                2023-09-06 16:57:02 UTC (releng/13.2, 13.2-RELEASE-p3)

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

FreeBSD's pcib(4) PCI-e bridge driver implements support for hot-plugging PCIe
devices.  When attaching to a hot-plug-capable slot, the pcib(4) driver
allocates a MSI or MSI-X vector used to trigger handling of hot-plug
events.

II.  Problem Description

The code which allocated the hot-plug interrupt did not allocate MSI-X
vectors properly.  When attaching to devices which support only MSI-X
messages, the interrupt would not be allocated.

III. Impact

PCIe hot-plug would fail to work for certain devices.  In particular,
this affects certain Amazon EC2 instance types which require functional
hot-plug support in order to attach network devices.

IV.  Workaround

No workaround is available for affected devices.

V.   Solution

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

Perform one of the following:

1) To update your system via a binary patch:

Systems running a RELEASE version of FreeBSD on the amd64, i386, or
(on FreeBSD 13 and later) arm64 platforms can be updated via the
freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install
# shutdown -r +10min "Rebooting for an erratum update"

2) 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-23:10/pci.patch
# fetch https://security.FreeBSD.org/patches/EN-23:10/pci.patch.asc
# gpg --verify pci.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

This issue is corrected by the corresponding Git commit hash or Subversion
revision number in the following stable and release branches:

Branch/path                             Hash                     Revision
- -------------------------------------------------------------------------
stable/13/                              12ce57e6d3e7    stable/13-n255700
releng/13.2/                            e80d2d894ff1  releng/13.2-n254629
- -------------------------------------------------------------------------

Run the following command to see which files were modified by a
particular commit:

# git show --stat <commit hash>

Or visit the following URL, replacing NNNNNN with the hash:

<URL:https://cgit.freebsd.org/src/commit/?id=NNNNNN>

To determine the commit count in a working tree (for comparison against
nNNNNNN in the table above), run:

# git rev-list --count --first-parent HEAD

VII. References

<URL:https://reviews.freebsd.org/D40581>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-23:10.pci.asc>
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