[libvirt PATCH 1/2] conf: support stateless UEFI firmware

[Michal Prívozník]

On 7/22/22 18:23, Daniel P. Berrangé wrote:
> Normally when an UEFI firmware is marked as read-only, an associated
> NVRAM file will be created. Some builds of UEFI firmware, however, wish
> to remain stateless and so will be read-only, but never have any NVRAM
> file. To represent this concept a 'stateless' tristate bool attribute
> is introduced on the <loader/> element.
> 
> There are rather a large number of permutations to consider.
> 
> With default firmware selection
> 
>   *  <os/>
> 
>      => Historic default, no change
> 
>   *  <os>
>        <loader stateless='yes'/>
>      </os>
> 
>      => Explicit version of historic default, no change
> 
>   *  <os>
>        <loader stateless='no'/>
>      </os>
> 
>       => Invalid, bios is always stateless
> 
> With manual legacy BIOS selection
> 
>   *  <os>
>        <loader>/path/to/seabios</loader>
>        ...
>      </os>
> 
>      => Historic default, no change
> 
>   *  <os>
>        <loader stateless='yes'>/path/to/seabios</loader>
>        ...
>      </os>
> 
>      => Explicit version of historic default, no change
> 
>   *  <os>
>        <loader stateless='no'>/path/to/seabios</loader>
>        ...
>      </os>
> 
>       => Invalid, bios is always stateless
> 
> With manual UEFI selection
> 
>   *  <os>
>        <loader type='pflash'>/path/to/edk2</loader>
>        ...
>      </os>
> 
>      => Historic default, no change
> 
>   *  <os>
>        <loader type='pflash' stateless='yes'>/path/to/edk2</loader>
>        ...
>      </os>
> 
>      => Skip auto-filling NVRAM / template
> 
>   *  <os>
>        <loader type='pflash' stateless='no'>/path/to/edk2</loader>
>        ...
>      </os>
> 
>      => Explicit version of historic default, no change
> 
> With automatic firmware selection
> 
>   *  <os firmware='bios'/>
> 
>      => Historic default, no change
> 
>   *  <os firmware='bios'>
>        <loader stateless='yes'/>
>      </os>
> 
>      => Explicit version of historic default, no change
> 
>   *  <os firmware='bios'>
>        <loader stateless='no'/>
>      </os>
> 
>       => Invalid, bios is always stateless
> 
>   *  <os firmware='uefi'/>
> 
>      => Historic default, no change
> 
>   *  <os firmware='uefi'>
>        <loader stateless='yes'/>
>      </os>
> 
>      => Skip auto-filling NVRAM / template
> 
>   *  <os firmware='uefi'>
>        <loader stateless='no'/>
>      </os>
> 
>      => Explicit version of historic default, no change
> 
> Signed-off-by: Daniel P. Berrangé <berrange at redhat.com>
> ---
>  docs/formatdomain.rst                         |  9 ++++-
>  src/conf/domain_conf.c                        |  9 +++++
>  src/conf/domain_conf.h                        |  1 +
>  src/conf/domain_validate.c                    | 26 ++++++++++++++
>  src/conf/schemas/domaincommon.rng             |  5 +++
>  ...-auto-bios-not-stateless.x86_64-latest.err |  1 +
>  .../firmware-auto-bios-not-stateless.xml      | 18 ++++++++++
>  ...are-auto-bios-stateless.x86_64-latest.args | 32 +++++++++++++++++
>  .../firmware-auto-bios-stateless.xml          | 18 ++++++++++
>  .../firmware-manual-bios-not-stateless.err    |  1 +
>  .../firmware-manual-bios-not-stateless.xml    | 15 ++++++++
>  .../firmware-manual-bios-stateless.args       | 30 ++++++++++++++++
>  .../firmware-manual-bios-stateless.xml        | 15 ++++++++
>  ...nual-efi-nvram-stateless.x86_64-latest.err |  1 +
>  .../firmware-manual-efi-nvram-stateless.xml   | 21 ++++++++++++
>  ...nvram-template-stateless.x86_64-latest.err |  1 +
>  ...re-manual-efi-nvram-template-stateless.xml | 19 +++++++++++
>  tests/qemuxml2argvtest.c                      |  8 +++++
>  ...ware-auto-bios-stateless.x86_64-latest.xml | 34 +++++++++++++++++++
>  .../firmware-manual-bios-stateless.xml        | 25 ++++++++++++++
>  .../firmware-manual-bios.xml                  | 25 ++++++++++++++
>  tests/qemuxml2xmltest.c                       |  3 ++
>  22 files changed, 316 insertions(+), 1 deletion(-)
>  create mode 100644 tests/qemuxml2argvdata/firmware-auto-bios-not-stateless.x86_64-latest.err
>  create mode 100644 tests/qemuxml2argvdata/firmware-auto-bios-not-stateless.xml
>  create mode 100644 tests/qemuxml2argvdata/firmware-auto-bios-stateless.x86_64-latest.args
>  create mode 100644 tests/qemuxml2argvdata/firmware-auto-bios-stateless.xml
>  create mode 100644 tests/qemuxml2argvdata/firmware-manual-bios-not-stateless.err
>  create mode 100644 tests/qemuxml2argvdata/firmware-manual-bios-not-stateless.xml
>  create mode 100644 tests/qemuxml2argvdata/firmware-manual-bios-stateless.args
>  create mode 100644 tests/qemuxml2argvdata/firmware-manual-bios-stateless.xml
>  create mode 100644 tests/qemuxml2argvdata/firmware-manual-efi-nvram-stateless.x86_64-latest.err
>  create mode 100644 tests/qemuxml2argvdata/firmware-manual-efi-nvram-stateless.xml
>  create mode 100644 tests/qemuxml2argvdata/firmware-manual-efi-nvram-template-stateless.x86_64-latest.err
>  create mode 100644 tests/qemuxml2argvdata/firmware-manual-efi-nvram-template-stateless.xml
>  create mode 100644 tests/qemuxml2xmloutdata/firmware-auto-bios-stateless.x86_64-latest.xml
>  create mode 100644 tests/qemuxml2xmloutdata/firmware-manual-bios-stateless.xml
>  create mode 100644 tests/qemuxml2xmloutdata/firmware-manual-bios.xml
> 
> diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
> index 3ea094e64c..4199abfd1a 100644
> --- a/docs/formatdomain.rst
> +++ b/docs/formatdomain.rst
> @@ -242,7 +242,11 @@ harddisk, cdrom, network) determining where to obtain/find the boot image.
>     firmwares may implement the Secure boot feature. Attribute ``secure`` can be
>     used to tell the hypervisor that the firmware is capable of Secure Boot feature.
>     It cannot be used to enable or disable the feature itself in the firmware.
> -   :since:`Since 2.1.0`
> +   :since:`Since 2.1.0`. If the loader is marked as read-only, then with UEFI it
> +   is assumed that there will be a writable NVRAM available. In some cases,
> +   however, it may be desirable for the loader to run without any NVRAM, discarding
> +   any config changes on shutdown. The ``stateless`` flag can be used to control
> +   this behaviour, when set to ``no`` NVRAM will never be created.

The ``stateless` flag (:since:since 8.6.0) can be used ...
Or something among those lines, to make it obvious when the attribute
was added.

>  ``nvram``
>     Some UEFI firmwares may want to use a non-volatile memory to store some
>     variables. In the host, this is represented as a file and the absolute path

Michal