
=== OVMF OVERVIEW ===

The Open Virtual Machine Firmware (OVMF) project aims
to support firmware for Virtual Machines using the edk2
code base.  More information can be found at:

http://www.tianocore.org/ovmf/

=== STATUS ===

Current capabilities:
* X64 architecture (optionally with IA32 SEC/PEI)
* QEMU (version 1.7.1 or later, with 1.7 or later machine types)
  - Video, keyboard, IDE, CD-ROM, serial
  - Runs UEFI shell
  - Optional NIC support.
* UEFI Linux boots
* UEFI Windows 8 boots
* UEFI Windows 7 & Windows 2008 Server boot (see important notes below!)

=== FUTURE PLANS ===

* Test/Stabilize UEFI Self-Certification Tests (SCT) results

=== BUILDING OVMF ===

Pre-requisites:
* Build environment capable of build the edk2 MdeModulePkg.
* A properly configured ASL compiler:
  - Intel ASL compiler: Available from
    https://www.intel.com/content/www/us/en/developer/topic-technology/open/acpica/download.html
  - Microsoft ASL compiler: Available from
    https://learn.microsoft.com/en-us/windows-hardware/drivers/bringup/microsoft-asl-compiler
* NASM: https://www.nasm.us/

Update Conf/target.txt ACTIVE_PLATFORM for OVMF:
                             PEI arch   DXE arch   UEFI interfaces
* OvmfPkg/OvmfPkgIa32X64.dsc   IA32       X64            X64
* OvmfPkg/OvmfPkgX64.dsc       X64        X64            X64

Update Conf/target.txt TARGET_ARCH based on the .dsc file:
                             TARGET_ARCH
* OvmfPkg/OvmfPkgIa32X64.dsc  IA32 X64
* OvmfPkg/OvmfPkgX64.dsc      X64

Following the edk2 build process, you will find the OVMF binaries
under the $WORKSPACE/Build/*/*/FV directory.  The actual path will
depend on how your build is configured.  You can expect to find
these binary outputs:
* OVMF.FD
  - Please note!  This filename has changed.  Older releases used OVMF.Fv.
* OvmfVideo.rom
  - This file is not built separately any longer, starting with svn r13520.

If you are new to building in edk2 or looking for the latest build
instructions, visit <https://www.tianocore.org/tianocore-wiki.github.io/build-tooling/build-workflows/build_instructions.html>

More OVMF-specific build information can be found at:

[How to Build OVMF](https://www.tianocore.org/tianocore-wiki.github.io/development/tutorials-howto/how_to_build_ovmf.html)

=== RUNNING OVMF on QEMU ===

* Be sure to use qemu-system-x86_64, if you are using an X64 firmware.
  (qemu-system-x86_64 works for the IA32 SEC/PEI as well, of course.)
* Use OVMF for QEMU firmware (3 options available)
  - Option 1: Use QEMU -pflash parameter
    * QEMU/OVMF will use emulated flash, and fully support UEFI variables
    * Run qemu with: -pflash path/to/OVMF.fd
    * Note that this option is required for running SecureBoot-enabled builds
      (-D SECURE_BOOT_ENABLE).
  - Option 2: Use QEMU -bios parameter
    * Note that UEFI variables will be partially emulated, and non-volatile
      variables may lose their contents after a reboot
    * Run qemu with: -bios path/to/OVMF.fd
  - Option 3: Use QEMU -L parameter
    * Note that UEFI variables will be partially emulated, and non-volatile
      variables may lose their contents after a reboot
    * Either copy, rename or symlink OVMF.fd => bios.bin
    * Use the QEMU -L parameter to specify the directory where the bios.bin
      file is located.
* The EFI shell is built into OVMF builds at this time, so it should
  run automatically if a UEFI boot application is not found on the
  removable media.
* On Linux, newer version of QEMU may enable KVM feature, and this might
  cause OVMF to fail to boot.  The QEMU '-no-kvm' may allow OVMF to boot.
* Capturing OVMF debug messages on qemu:
  - The default OVMF build writes debug messages to IO port 0x402.  The
    following qemu command line options save them in the file called
    debug.log: '-debugcon file:debug.log -global isa-debugcon.iobase=0x402'.
  - It is possible to revert to the original behavior, when debug messages were
    written to the emulated serial port (potentially intermixing OVMF debug
    output with UEFI serial console output).  For this the
    '-D DEBUG_ON_SERIAL_PORT' option has to be passed to the build command (see
    the next section), and in order to capture the serial output qemu needs to
    be started with eg. '-serial file:serial.log'.
  - Debug messages fall into several categories.  Logged vs. suppressed
    categories are controlled at OVMF build time by the
    'gEfiMdePkgTokenSpaceGuid.PcdDebugPrintErrorLevel' bitmask (an UINT32
    value) in the selected .dsc file.  Individual bits of this bitmask are
    defined in <MdePkg/Include/Library/DebugLib.h>.  One non-default bit (with
    some performance impact) that is frequently set for debugging is 0x00400000
    (DEBUG_VERBOSE).
  - The RELEASE build target ('-b RELEASE' build option, see below) disables
    all debug messages.  The default build target is DEBUG.

=== Build Scripts ===

On systems with the bash shell you can use OvmfPkg/build.sh to simplify
building and running OVMF.

So, for example, to build + run OVMF X64:
$ OvmfPkg/build.sh -a X64
$ OvmfPkg/build.sh -a X64 qemu

And to run a 64-bit UEFI bootable ISO image:
$ OvmfPkg/build.sh -a X64 qemu -cdrom /path/to/disk-image.iso

=== Secure Boot ===

Secure Boot is a security feature that ensures only trusted and digitally
signed software is allowed to run during the boot process. This is achieved
by storing Secure Boot keys in UEFI Variables, as result it can be easily
bypassed by writing directly to the flash varstore. To avoid this situation,
it's necessary to make the varstore with SB keys read-only and/or provide an
isolated execution environment for flash access (such as SMM).

* In order to support Secure Boot, OVMF must be built with the
  "-D SECURE_BOOT_ENABLE" option.

* By default, OVMF is not shipped with any SecureBoot keys installed. The user
  need to install them with "Secure Boot Configuration" utility in the firmware
  UI, or enroll the default UEFI keys using the OvmfPkg/EnrollDefaultKeys app.

  For the EnrollDefaultKeys application, the hypervisor is expected to add a
  string entry to the "OEM Strings" (Type 11) SMBIOS table. The string should
  have the following format:

    4e32566d-8e9e-4f52-81d3-5bb9715f9727:<Base64 X509 cert for PK and first KEK>

  Such string can be generated with the following script, for example:

    sed \
      -e 's/^-----BEGIN CERTIFICATE-----$/4e32566d-8e9e-4f52-81d3-5bb9715f9727:/' \
      -e '/^-----END CERTIFICATE-----$/d' \
      PkKek1.pem \
    | tr -d '\n' \
    > PkKek1.oemstr

  - Using QEMU 5.2 or later, the SMBIOS type 11 field can be specified from a
    file:

    -smbios type=11,path=PkKek1.oemstr \

  - Using QEMU 5.1 or earlier, the string has to be passed as a value:

    -smbios type=11,value="$(< PkKek1.oemstr)"

=== SMM support ===

Requirements:
* SMM support requires QEMU 2.5.
* The minimum required QEMU machine type is "pc-q35-2.5".
* SMM with KVM requires Linux 4.4 (host).

OVMF is capable of utilizing SMM if the underlying QEMU or KVM hypervisor
emulates SMM. SMM is put to use in the S3 suspend and resume infrastructure,
and in the UEFI variable driver stack. The purpose is (virtual) hardware
separation between the runtime guest OS and the firmware (OVMF), with the
intent to make Secure Boot actually secure, by preventing the runtime guest OS
from tampering with the variable store and S3 areas.

For SMM support, OVMF must be built with the "-D SMM_REQUIRE" option. The
resultant firmware binary will check if QEMU actually provides SMM emulation;
if it doesn't, then OVMF will log an error and trigger an assertion failure
during boot (even in RELEASE builds). Both the naming of the flag (SMM_REQUIRE,
instead of SMM_ENABLE), and this behavior are consistent with the goal
described above: this is supposed to be a security feature, and fallbacks are
not allowed. Similarly, a pflash-backed variable store is a requirement.

QEMU should be started with the options listed below (in addition to any other
guest-specific flags). The command line should be gradually composed from the
hints below. '\' is used to extend the command line to multiple lines, and '^'
can be used on Windows.

* QEMU binary and options specific to 32-bit guests:

  $ qemu-system-i386 -cpu coreduo,-nx \

  or

  $ qemu-system-x86_64 -cpu <MODEL>,-lm,-nx \

* QEMU binary for running 64-bit guests (no particular options):

  $ qemu-system-x86_64 \

* Flags common to all SMM scenarios (only the Q35 machine type is supported):

  -machine q35,smm=on,accel=(tcg|kvm) \
  -m ... \
  -smp ... \
  -global driver=cfi.pflash01,property=secure,value=on \
  -drive if=pflash,format=raw,unit=0,file=OVMF_CODE.fd,readonly=on \
  -drive if=pflash,format=raw,unit=1,file=copy_of_OVMF_VARS.fd \

* In order to disable S3, add:

  -global ICH9-LPC.disable_s3=1 \

=== Standalone MM Support ===

Standalone MM (Management Mode) in UEFI is a secure execution environment
provided by the CPU and related silicon, designed to improve security and
portability compared to Traditional MM. It operates independently of the DXE
(Driver Execution Environment) phase, ensuring better isolation and reducing
vulnerabilities.

Standalone MM leverages the same hardware capabilities as Traditional MM but
revises the software model to address security challenges. It uses Management
Mode RAM (MMRAM) for executing drivers and protocols securely, and its
initialization and runtime phases are distinct from Traditional MM.

Due to the nature of Standalone MM, there are some limitations, requirements and
considerations when using it in OVMF:

* The Standalone MM driver must be built with `-D STANDALONE_MM_ENABLE` flag.
* For X64, Standalone MM does not currently support S3 resume or LockBox
  functionality. While LockBox functionality could be supported in the future
  with unblock memory enabled during the DXE phase, S3 resume support is not
  planned.
* On OVMF, Standalone MM does not support CPU hotplugging at this time; however,
  this feature may be enabled in the future.
* Similar to SMM, Standalone MM requires a pflash-backed variable store.
* Standalone MM framework copies the entire Firmware Volume (FV) containing the
  Standalone MM core into MMRAM. As a result, MMRAM must have sufficient
  capacity to accommodate this operation alongside the runtime-loaded drivers.

* Example QEMU launching command for Standalone MM based Q35 machine type:

  $ qemu-system-x86_64 \
  -debugcon stdio \
  -smp 4 -cpu IvyBridge,+rdrand \
  -machine q35,smm=on --accel tcg,thread=single \
  -global driver=cfi.pflash01,property=secure,value=on \
  -drive if=pflash,format=raw,unit=0,file=OVMF_CODE.fd,readonly=on \
  -drive if=pflash,format=raw,unit=1,file=OVMF_VARS.fd \
  -global ICH9-LPC.disable_s3=1 \
  -global mch.extended-tseg-mbytes=32

=== Network Support ===

OVMF provides a UEFI network stack by default. Its lowest level driver is the
NIC driver, higher levels are generic. In order to make DHCP, PXE Boot, and eg.
socket test utilities from the StdLib edk2 package work, (1) qemu has to be
configured to emulate a NIC, (2) a matching UEFI NIC driver must be available
when OVMF boots.

(If a NIC is configured for the virtual machine, and -- dependent on boot order
-- PXE booting is attempted, but no DHCP server responds to OVMF's DHCP
DISCOVER message at startup, the boot process may take approx. 3 seconds
longer.)

* For each NIC emulated by qemu, a GPLv2 licensed UEFI driver is available from
  the iPXE project. The qemu source distribution contains prebuilt binaries of
  these drivers (and of course allows one to rebuild them from source as well).
  This is the recommended set of drivers.

* Use the qemu -netdev and -device options, or the legacy -net option, to
  enable NIC support: <http://wiki.qemu.org/Documentation/Networking>.

* The iPXE drivers are automatically available to and configured for OVMF in
  the default qemu installation.

* Independently of the iPXE NIC drivers, the default OVMF build provides a
  basic virtio-net driver, located in OvmfPkg/VirtioNetDxe.

* Also independently of the iPXE NIC drivers, Intel's proprietary E1000 NIC
  driver can be embedded in the OVMF image at build time:

  - Download Intel Ethernet Adapter Driver Pack:
    - Navigate to
      https://www.intel.com/content/www/us/en/download/15084/intel-ethernet-adapter-complete-driver-pack.html
    - Select version 23.5.2 and click the download link for "23_5_2.zip".
    - Accept the Intel Software License Agreement that appears.
    - Unzip "23_5_2.zip" into a separate directory.
    - Copy the "APPS/EFI/EFIx64/E3522X2.EFI" driver binary to
      "Intel3.5/EFIX64/E3522X2.EFI" in your WORKSPACE.

  - Include the driver in OVMF during the build:
    - Add "-D E1000_ENABLE" to your build command (only when building
      "OvmfPkg/OvmfPkgIa32X64.dsc" or "OvmfPkg/OvmfPkgX64.dsc").
    - For example: "build -D E1000_ENABLE".

* When a matching iPXE driver is configured for a NIC as described above, it
  takes priority over other drivers that could possibly drive the card too:

                            | e1000  ne2k_pci  pcnet  rtl8139  virtio-net-pci
    ------------------------+------------------------------------------------
    iPXE                    |   x       x        x       x           x
    VirtioNetDxe            |                                        x
    Intel E3522X2.EFI (X64) |   x

=== HTTPS Boot ===

HTTPS Boot is an alternative solution to PXE. It replaces the tftp server
with a HTTPS server so the firmware can download the images through a trusted
and encrypted connection.

* To enable HTTPS Boot, you have to build OVMF with -D NETWORK_HTTP_BOOT_ENABLE
  and -D NETWORK_TLS_ENABLE. The former brings in the HTTP stack from
  NetworkPkg while the latter enables TLS support in both NetworkPkg and
  CryptoPkg.

  If you want to exclude the unsecured HTTP connection completely, OVMF has to
  be built with -D NETWORK_ALLOW_HTTP_CONNECTIONS=FALSE so that only the HTTPS
  connections will be accepted.

* By default, there is no trusted certificate. The user has to import the
  certificates either manually with "TLS Auth Configuration" utility in the
  firmware UI or through the fw_cfg entry, etc/edk2/https/cacerts.

  -fw_cfg name=etc/edk2/https/cacerts,file=<certdb>

  The blob for etc/edk2/https/cacerts has to be in the format of Signature
  Database(*1). You can use p11-kit(*2) or efisiglit(*3) to create the
  certificate list.

  If you want to create the certificate list based on the CA certificates
  in your local host, p11-kit will be a good choice. Here is the command to
  create the list:

  p11-kit extract --format=edk2-cacerts --filter=ca-anchors \
    --overwrite --purpose=server-auth <certdb>

  If you only want to import one certificate, efisiglist is the tool for you:

  efisiglist -a <cert file> -o <certdb>

  Please note that the certificate has to be in the DER format.

  You can also append a certificate to the existing list with the following
  command:

  efisiglist -i <old certdb> -a <cert file> -o <new certdb>

  NOTE: You may need the patch to make efisiglist generate the correct header.
  (https://github.com/rhboot/pesign/pull/40)

* Besides the trusted certificates, it's also possible to configure the trusted
  cipher suites for HTTPS through another fw_cfg entry: etc/edk2/https/ciphers.

  OVMF expects a binary UINT16 array which comprises the cipher suites HEX
  IDs(*4). If the cipher suite list is given, OVMF will choose the cipher
  suite from the intersection of the given list and the built-in cipher
  suites. Otherwise, OVMF just chooses whatever proper cipher suites from the
  built-in ones.

  - Using QEMU 5.2 or later, QEMU can expose the ordered list of permitted TLS
    cipher suites from the host side to OVMF:

  -object tls-cipher-suites,id=mysuite0,priority=@SYSTEM \
  -fw_cfg name=etc/edk2/https/ciphers,gen_id=mysuite0

  (Refer to the QEMU manual and to
  <https://gnutls.org/manual/html_node/Priority-Strings.html> for more
  information on the "priority" property.)

  - Using QEMU 5.1 or earlier, the array has to be passed from a file:

  -fw_cfg name=etc/edk2/https/ciphers,file=<cipher suites>

  whose contents can be generated with the following script, for example:

  export LC_ALL=C
  openssl ciphers -V \
  | sed -r -n \
     -e 's/^ *0x([0-9A-F]{2}),0x([0-9A-F]{2}) - .*$/\\\\x\1 \\\\x\2/p' \
  | xargs -r -- printf -- '%b' > ciphers.bin

  This script creates ciphers.bin that contains all the cipher suite IDs
  supported by openssl according to the local host configuration.

  You may want to enable only a limited set of cipher suites. Then, you
  should check the validity of your list first:

  openssl ciphers -V <cipher list>

  If all the cipher suites in your list map to the proper HEX IDs, go ahead
  to modify the script and execute it:

  export LC_ALL=C
  openssl ciphers -V <cipher list> \
  | sed -r -n \
     -e 's/^ *0x([0-9A-F]{2}),0x([0-9A-F]{2}) - .*$/\\\\x\1 \\\\x\2/p' \
  | xargs -r -- printf -- '%b' > ciphers.bin

(*1) See "31.4.1 Signature Database" in UEFI specification 2.7 errata A.
(*2) p11-kit: https://github.com/p11-glue/p11-kit/
(*3) efisiglist: https://github.com/rhboot/pesign/blob/master/src/efisiglist.c
(*4) https://wiki.mozilla.org/Security/Server_Side_TLS#Cipher_names_correspondence_table

=== OVMF Flash Layout ===

Like all current IA32/X64 system designs, OVMF's firmware device (rom/flash)
appears in QEMU's physical address space just below 4GB (0x100000000).

OVMF supports building a 1MB, 2MB or 4MB flash image (see the DSC files for the
FD_SIZE_1MB, FD_SIZE_2MB, FD_SIZE_4MB build defines). The base address for the
1MB image in QEMU physical memory is 0xfff00000. The base address for the 2MB
image is 0xffe00000. The base address for the 4MB image is 0xffc00000.

Using the 1MB or 2MB image, the layout of the firmware device in memory looks
like:

+--------------------------------------- 4GB (0x100000000)
| VTF0 (16-bit reset code) and OVMF SEC
| (SECFV, 208KB/0x34000)
+--------------------------------------- varies based on flash size
|
| Compressed main firmware image
| (FVMAIN_COMPACT)
|
+--------------------------------------- base + 0x20000
| Fault-tolerant write (FTW)
| Spare blocks (64KB/0x10000)
+--------------------------------------- base + 0x10000
| FTW Work block (4KB/0x1000)
+--------------------------------------- base + 0x0f000
| Event log area (4KB/0x1000)
+--------------------------------------- base + 0x0e000
| Non-volatile variable storage
| area (56KB/0xe000)
+--------------------------------------- base address

Using the 4MB image, the layout of the firmware device in memory looks like:

+--------------------------------------- base + 0x400000 (4GB/0x100000000)
| VTF0 (16-bit reset code) and OVMF SEC
| (SECFV, 208KB/0x34000)
+--------------------------------------- base + 0x3cc000
|
| Compressed main firmware image
| (FVMAIN_COMPACT, 3360KB/0x348000)
|
+--------------------------------------- base + 0x84000
| Fault-tolerant write (FTW)
| Spare blocks (264KB/0x42000)
+--------------------------------------- base + 0x42000
| FTW Work block (4KB/0x1000)
+--------------------------------------- base + 0x41000
| Event log area (4KB/0x1000)
+--------------------------------------- base + 0x40000
| Non-volatile variable storage
| area (256KB/0x40000)
+--------------------------------------- base address (0xffc00000)

The code in SECFV locates FVMAIN_COMPACT, and decompresses the
main firmware (MAINFV) into RAM memory at address 0x800000. The
remaining OVMF firmware then uses this decompressed firmware
volume image.

=== UEFI Windows 7 & Windows 2008 Server ===

* One of the '-vga std' and '-vga qxl' QEMU options should be used.
* Only one video mode, 1024x768x32, is supported at OS runtime.
* The '-vga qxl' QEMU option is recommended. After booting the installed
  guest OS, select the video card in Device Manager, and upgrade its driver
  to the QXL XDDM one. Download location:
  <http://www.spice-space.org/download.html>, Guest | Windows binaries.
  This enables further resolutions at OS runtime, and provides S3
  (suspend/resume) capability.