OVMF: Difference between revisions

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== Intro ==
OVMF "is a project to enable UEFI support for Virtual Machines".


OVMF "is a project to enable UEFI support for Virtual Machines". This page tries to give yet another mini-howto about playing with OVMF boot firmware in qemu-kvm virtual machines plus libvirt, deferring heavily to the TianoCore upstream wiki. <em>Do</em> mercilessly edit any inaccuracies or wrong statements.
The earlier contents of this article have been replaced with the following link to the OVMF whitepaper:


This page is written as of edk2 svn rev 14423 (virtio-blk, virtio-scsi and virtio-net are supported, and several guests can be booted with, and recognize secure boot). For using OVMF directly with the qemu command line, refer to the [https://github.com/tianocore/edk2/blob/master/OvmfPkg/README README]; this page tries to detail OVMF usage under (RHEL-6.4) libvirt.
http://www.linux-kvm.org/downloads/lersek/ovmf-whitepaper-c770f8c.txt


The recommended way for testing OVMF is installing Gerd Hoffman's RPM packages from his repo at http://www.kraxel.org/repos/, using yum. (The package to install is <code>edk2.git-ovmf-x64</code>; yum will pull in several dependencies from the repo.)
The whitepaper covers everything this article used to cover, and the whitepaper is much more up-to-date and extensive. Please use the History link near the bottom if you'd like to see the previous (now stale) contents.
 
The firmware images are located in the <code>/usr/share/edk2.git/ovmf-x64</code> directory. <code>OVMF-pure-efi.fd</code> is a "pure UEFI" image, while <code>OVMF-with-csm.fd</code> includes the Compatibility Support Module (CSM) build of SeaBIOS. <code>bios.bin</code> is a symlink to the latter. Both images support Secure Boot.
 
== Building from source ==
 
Clone either the main SVN repository (git svn recommended) or one of the git mirrors listed in the [http://sourceforge.net/apps/mediawiki/tianocore/index.php?title=Source_Control TianoCore wiki].
 
=== Frequent rebuilds ===
 
For developers it is recommended to create a branch called <code>base_config</code> or something similar off the master branch (in the git svn or plain git clone), capture the config steps described [http://sourceforge.net/apps/mediawiki/tianocore/index.php?title=How_to_build_OVMF here] in commits (including setting up a reasonable <code>.gitignore</code> file), and keep rebasing <code>base_config</code> after <code>git svn rebase --use-log-author</code> / <code>git pull</code> commands. Fork/rebase your own development branches off/to <code>base_config</code>.
 
The very first time you build the tree, and after <code>git clean -fdx</code> commands, you must (re)build BaseTools with <code>make -C "$EDK_TOOLS_PATH"</code>. (You're going to have that variable set in your environment after sourcing <code>edksetup.sh</code> in the root project dir; see the [http://sourceforge.net/apps/mediawiki/tianocore/index.php?title=OVMF TianoCore Wiki] again.)
 
=== One-off builds ===
 
<code>OvmfPkg/build.sh</code> takes care of BaseTools, configuration (according to command line options) and the main build. One potentially useful option is <code>-n THREADNUMBER</code>, which enables parallel make.
 
<code>-D FLAG</code> options control optional build features/aspects. Consult <code>OvmfPkg/build.sh</code>, <code>OvmfPkg/README</code>, the <code>OvmfPkg/*.dsc</code> and <code>OvmfPkg/*.fdf</code> files, and Gerd's SRPMs.
 
== Using the firmware image with libvirt ==
 
The boot firmware is set in the domain XML file under the <code>/domain/os/loader</code> element.
 
Neither <code>virt-manager</code> nor <code>virt-install</code> seem to expose this XML node on RHEL-6.4. The following list of commands is one workaround. The <code>EMULATOR</code> bit is discussed later -- it is useful to have a wrapper script in place, between libvirt and qemu, to add custom options.
 
<pre>
# "configuration"
NAME=set_guest_name_here
INSTALL_ISO=/full/path/to/install/iso
DRIVER_ISO=/full/path/to/virtio/driver/iso
EMULATOR=/full/path/to/emulator
LOADER=/full/path/to/OVMF.fd
 
# create a domain XML template for guest installation:
# - 4 VCPUs, 4G RAM
# - virtio target disk, 25 GB in size
# - first IDE CD-ROM has install disk
# - second IDE CD-ROM has virtio driver disk
#  (should only be necessary for proprietary guests without built-in drivers)
TARGET_DISK=/var/lib/libvirt/images/"$NAME".img
virt-install                                                                \
    --connect=qemu:///system                                                \
    --name=$NAME                                                            \
    --ram=4096                                                              \
    --arch=x86_64                                                            \
    --machine=rhel6.4.0                                                      \
    --vcpus=4                                                                \
    --boot=cdrom,hd                                                          \
    --disk=path=$TARGET_DISK,size=25,bus=virtio,format=qcow2                \
    --disk=path=$INSTALL_ISO,device=cdrom,bus=ide,perms=ro,format=raw        \
    --disk=path=$DRIVER_ISO,device=cdrom,bus=ide,perms=ro,format=raw        \
    --print-step=1                                                          \
| xmlstarlet ed -u /domain/devices/emulator                    -v $EMULATOR \
                -s /domain/os                -t elem -n loader -v $LOADER  \
    >template.xml
 
# Import the template to libvirt
virsh define template.xml
 
# Now customize the guest further with "virsh edit" or inside virt-manager,
# then start the installation.
</pre>
 
For a virtio-scsi disk, apply the following changes:
 
<ol>
<li>in the <code>TARGET_DISK</code> specification, replace <code>bus=virtio</code> with <code>bus=scsi</code>,</li>
<li>append the following options to the <code>xmlstarlet</code> command line:
<pre>
                -s /domain/devices            -t elem -n controller -v ''          \
                -s /domain/devices/controller -t attr -n type      -v scsi        \
                -s /domain/devices/controller -t attr -n model      -v virtio-scsi \
</pre>
</li>
</ol>
 
 
 
== Saving OVMF debug messages ==
 
Debug log verbosity is controlled at build time. See the <code>gEfiMdePkgTokenSpaceGuid.PcdDebugPrintErrorLevel</code> bitmask in <code>OvmfPkg/OvmfPkgX64.dsc</code>. The individual bits (<code>DEBUG_*</code> macros) are explained in <code>MdePkg/Include/Library/DebugLib.h</code>.
 
=== serial console ===
 
Debug messages are written to the qemu debug port per default (see below), but they can be redirected to the (virtual) serial console with the <code>-D DEBUG_ON_SERIAL_PORT</code> option at build time. In this case however the serial console will intermix framework debug messages with the TUI of the (U)EFI shell and other UEFI applications.
 
=== qemu debug port ===
 
This is where the debug messages are written by default, but capturing them on the host requires the <code>-debugcon DEV -global isa-debugcon.iobase=0x402</code> qemu-kvm command line switches. These can be set on a guest-by-guest basis in the libvirt VM config XML files, using [http://libvirt.org/drvqemu.html#qemucommand qemu:arg].
 
Alternatively, one might contemplate a qemu-kvm wrapper script like the following:
 
<pre>
#!/bin/bash
set -e -C -u
 
NAME=0
for ARG in "$@"; do
  if [ x"$ARG" = x-name ]; then
    NAME=1
  elif [ $NAME -ne 0 ]; then
    FNAME="${TMPDIR:-/tmp}/$ARG".debug
    exec /usr/libexec/qemu-kvm "$@" \
        -debugcon file:"$FNAME" -global isa-debugcon.iobase=0x402
  fi
done
exec /usr/libexec/qemu-kvm "$@"
</pre>
 
The full path to the wrapper script is specified in the <code>/domain/devices/emulator</code> element of the libvirt guest XML.
 
The script is adapted to the fact that libvirt invokes the emulator in two forms. XML validation after <code>virsh edit</code> seems to invoke the emulator for verification purposes only, without the <code>-name</code> option. In this case no debug file should be created / rewritten. When libvirt starts the guest, the <code>-name</code> option is present, and the script constructs the logfile's name from the corresponding option-argument.
 
On an SELinux enabled system, the script's context should be set to that of the wrapped emulator, qemu-kvm. See <code>chcon --reference</code>.
 
Furthermore, on an SELinux enabled system, a new instance of the same guest will be seclabelled differently from the previous instance, and will fail to overwrite the debug log produced by the previous instance. This could be worked around perhaps by reconfiguring libvirt's labelling practices for the guest, or changing the SELinux profile, or (horribile dictu) flipping SELinux to permissive. Removing the debug file manually before starting the next instance of the guest is simplest.
 
(Needless to say, never do any of this in production.)
 
== Tested guest OS'en ==
 
=== Apparently working nicely ===
 
<ul>
<li>Fedora 18 Alpha (XFCE edition). [[#Confirmation of secure boot in Fedora 18|Secure boot tested]] as well.</li>
<li>RHEL-6.3. (Its grub does not support booting from a virtio-blk disk. See [[#Making guests use it]] how to specify a virtio-scsi boot disk.)</li>
<li>Windows 8 Consumer Preview Build 8250. [[#Confirmation of secure boot in Windows 8 Consumer Preview Build 8250|Secure boot tested]] as well. The fix for qemu-kvm [https://bugzilla.redhat.com/show_bug.cgi?id=854304 RHBZ#854304] may be necessary to run this guest. (Upstream qemu contains the [http://git.qemu.org/?p=qemu.git;a=commitdiff;h=4d09d37c6aa9a02b44b1fdb6268820fab92499bd fix] of course.)</li>
<li>Reportedly, Windows Server 2012.</li>
</ul>
 
=== Windows Server 2008 R2 SP1 ===
 
This guest does not work correctly. Its UEFI installer is composed of several programs, some being UEFI applications, and the last layer being the Windows Pre-Installation Environment, running on the Windows 2008 R2 kernel.
 
The UEFI applications before the last layer correctly use the OVMF GOP (graphics output protocol), which drives the emulated Cirrus 5446 video card. Unfortunately, the last layer (WinPE) has a hard dependency on VGA BIOS interrupt 0x10, which is not provided by any OVMF CSM (compatibility support module) as of now.
 
This <em>hard</em> dependency is a Windows 2008 R2 bug; the WinPE layer should (actively) inherit the linear framebuffer characteristics from the GOP (UEFI boot phase), and use that until the kernel-level graphics drivers are loaded.
 
One (quite shabby) workaround for the time being is automated installation of this OS on top of OVMF, and then connecting to it with <code>rdesktop</code>.
 
During most of the installation (ie. in the WinPE phase), nothing can be seen in the VNC window. The VM reboots several times, at which points <code>cdboot.efi</code> shortly displays a (visible) message, "press a key to continue booting from the installation CD". No key should be pressed, as expected, but after the timeout, <code>cdboot.efi</code> tends to crash, violating an edk2 framework ASSERT and falling into an infinite loop (watch the debug log).
 
If this happens, force off the VM, restart it, enter the OVMF setup utility, and manually set the on-hdd boot loader. The installation should resume then.
 
For the remote desktop connection, the IP address of the running guest can be fetched by searching <code>/var/lib/libvirt/dnsmasq/default.leases</code> for the guest's MAC address (which is present in its libvirt XML file).
 
An example <code>AutoUnattend.xml</code> file, and a corresponding guest XML template (to be used with <code>virsh define</code>) are inserted below as a base-64 encoded, xz-compressed tarball. (Unfortunately, File Upload refuses xml and xml.gz files.) The install ISO that was augmented with the <code>AutoUnattend.xml</code> file is named <code>en_windows_server_2008_r2_with_sp1_x64_dvd_617601.iso</code>, its SHA1 is <code>D3FD7BF85EE1D5BDD72DE5B2C69A7B470733CD0A</code>.
 
Note: the first <code>ProductKey</code> element in the XML is a default key from
<code>\SOURCES\PRODUCT.INI</code>. It does not participate in product
activation, it contributes to product <em>selection</em> at installation time.
 
<pre>
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</pre>
 
=== Confirmation of secure boot in Fedora 18 ===
 
(This is a write-up of an earlier test.)
 
<ol>
<li>I rebuilt OVMF with secure boot support.</li>
 
<li>I downloaded the x86_64 binary RPM for [http://koji.fedoraproject.org/koji/buildinfo?buildID=357608 pesign-0.10-5.fc18] and extracted the <code>/etc/pki/pesign</code> directory to <code>$HOME/tmp/f18-keys</code>.</li>
 
<li>I extracted two certificates in DER format, standing in <code>$HOME/tmp</code>:
 
<pre>
certutil -L -d f18-keys -n 'Red Hat Test Certificate' -r \
    >RedHatTestCertificate.der
 
certutil -L -d f18-keys -n 'Red Hat Test CA' -r \
    >RedHatTestCA.der
</pre>
</li>
 
<li>I created a 64MB zero file,</li>
 
<ul>
<li>set up <code>/dev/loop1</code> on it,</li>
<li>created an MBR partition table with one 0x0c partition (cfdisk),</li>
<li>(maybe ran <code>kpartx -a /dev/loop1</code>,)</li>
<li>formatted <code>/dev/mapper/loop1p1</code> as FAT32 with mkdosfs,</li>
<li>mounted it, created a directory called <code>Red Hat Secure Boot Keys</code>,</li>
<li>copied the output files from the previous step there.</li>
<li>NOTE: libguestfs / guestfish is a <em>much</em> better way to do the same.
</li>
</ul>
 
<li>I attached the above image file as second disk to my preexistent
guest while it was shut down.</li>
 
<li>I started the guest.</li>
 
<ul>
<li>As soon as the TianoCore splash screen showed, I entered the setup
menu and selected <code>Device Manager | Secure Boot Options</code>,</li>
<li>enrolled <code>RedHatTestCA.der</code> as PK.</li>
<li>enrolled <code>RedHatTestCertificate.der</code> as one KEK and one DB entry,</li>
<li>made sure <code>shim.efi</code> from the first disk was the first boot option in <code>Boot Maintenance Manager | Boot Options</code>,</li>
<li>allowed the boot to continue.</li>
</ul>
 
<li>
<code>shim.efi</code> printed <code>Binary is whitelisted</code>. grub2 printed <code>secure boot forbids insmod</code> four times. The F18 XFCE GUI started. The guest dmesg contains
 
<pre>
[    0.000000] Secure boot enabled
</pre>
</li>
 
<li>
OVMF secure boot configuration (enrolled keys etc) don't persist
across guest shutdown (maybe not even across in-guest reboot); OVMF
reverts to non-secure boot. Copying the certificates to the F18 boot
partition didn't change this. What's more, when OVMF is built with
Secure Boot support, even the boot order saved from last time is
forgotten and default options are regenerated (even with no keys enrolled).
</li>
</ol>
 
=== Confirmation of secure boot in Windows 8 Consumer Preview Build 8250 ===
 
(This is also a write-up of an earlier test.)
 
Basically re-executed [[#Confirmation of secure boot in Fedora 18]], with the following changes:
 
<ul>
<li>I downloaded the platform key, the key exchange key, and three DB entries from [http://blog.hansenpartnership.com/the-microsoft-keys/ James Bottomley's blog].</li>
<li>Once inside the guest, I [http://msdn.microsoft.com/en-us/library/windows/desktop/hh847889.aspx started PowerShell as an administrator] and
then [http://communities.intel.com/community/vproexpert/blog/2012/06/26/microsoft-windows-8--enabling-secure-boot verified that Secure Boot was enabled].</li>
</ul>

Latest revision as of 09:27, 10 March 2015

OVMF "is a project to enable UEFI support for Virtual Machines".

The earlier contents of this article have been replaced with the following link to the OVMF whitepaper:

http://www.linux-kvm.org/downloads/lersek/ovmf-whitepaper-c770f8c.txt

The whitepaper covers everything this article used to cover, and the whitepaper is much more up-to-date and extensive. Please use the History link near the bottom if you'd like to see the previous (now stale) contents.