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FreeBSD-EN-21:15.virtio                                         Errata Notice
                                                          The FreeBSD Project

Topic:          virtio(4) device probing fails

Category:       core
Module:         virtio
Announced:      2021-05-26
Affects:        FreeBSD 13.0
Corrected:      2021-04-03 06:09:50 UTC (stable/13, 13.0-STABLE)
                2021-05-26 20:32:40 UTC (releng/13.0, 13.0-RELEASE-p1)

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

VirtIO is a specification for para-virtualized I/O in a virtual machine
(VM).  It defines an interface for efficient I/O between the hypervisor
and VM.

II.  Problem Description

The virtio(4) driver on FreeBSD implemented support of the legacy
interface, which was released before the specification was formalized,
requiring certain characteristics that were different on some VMM
implementations.

III. Impact

FreeBSD will not boot on certain VMM implementations.

IV.  Workaround

No workaround is available.

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-21:15/virtio.patch
# fetch https://security.FreeBSD.org/patches/EN-21:15/virtio.patch.asc
# gpg --verify virtio.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/                              2e107638eac2    stable/13-n245094
releng/13.0/                            61acb3179a90  releng/13.0-n244741
- -------------------------------------------------------------------------

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

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-21:15.virtio.asc>
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