genode/doc/release_notes/17-08.txt

              ===============================================
              Release notes for the Genode OS Framework 17.08
              ===============================================

                               Genode Labs



The flagship feature of Genode 17.08 has been in the works for more than a
year: The support for hardware-accelerated graphics on Intel Gen-8 GPUs. This
is an especially challenging topic because it is riddled with terminology,
involves highly complex software stacks, carries a twisted history with it,
and remains to be a moving target. It took up a lot of patience to build up a
profound understanding of the existing driver architectures and the mechanisms
offered by modern graphics hardware. On the other hand, with the proliferation
of hardware-based sandboxing features like virtual GPU memory and hardware
contexts, we found that now is the perfect time for a clean-slate design of a
microkernelized GPU driver.
Section [Hardware-accelerated graphics for Intel Gen-8 GPUs] introduces this
work, which includes our new GPU multiplexer as well as the integration with
the client-side Mesa protocol stack.

The second focus of the current release is the extension of Genode's supported
base platforms. Most prominently, we upgrade the seL4 kernel to version 6.0
while extending the architecture support from 32-bit x86 to ARM and 64-bit
x86 (Section [The seL4 kernel on ARM and 64-bit x86 hardware]). To bring
Genode closer to cloud-computing scenarios, we added basic support for
executing Genode scenarios as Xen DomU domains (Section [Genode as Xen DomU]).
Furthermore, the Muen separation kernel has been updated to a current version.
As a cross-kernel effort, there is work under way to boot Genode-based
systems via UEFI, currently addressing the NOVA, base-hw, and seL4 kernels.

Among the many other functional additions are a new VFS plugin for accessing
FAT file systems, new components like _sequence_ and _fs_report_ that aid new
system compositions, and our evolving custom package-management
infrastructure.


Hardware-accelerated graphics for Intel Gen-8 GPUs
##################################################

The ability to leverage hardware-accelerated graphics is generally taken for
granted in modern commodity operating systems. The user experience of
modern desktop environments, web-browser performance, and obviously games
depend on it. On the other hand, the benefit of hardware-accelerated graphics
comes at the expense of tremendous added complexity in the lower software
stack, in particular in system components that need to be ultimately trusted.
For example, with circa 100 thousand lines of code, the Intel GPU driver in
the Linux kernel is an order of magnitude more complex than a complete modern
microkernel. In a monolithic-kernel-based system, this complexity is
generally neglected because the kernel is complex anyway. But in
microkernel-based scenarios optimized for a trusted computing base in the
order of a few ten thousand lines of code, it becomes unacceptable.
Fortunately, recent generations of graphics hardware provide a number of
hardware features that promise to solve this conflict, which prompted us to
investigate the use of these features for Genode.

During this year's Hack'n'Hike event, we ported the ioquake3 engine to Genode.
As preliminary requirement, we had to resurrect OpenGL support in our aging
graphics stack and enable support for current Intel HD Graphics devices (IGD).
We started by updating Mesa from the old 7.8.x to a more recent 11.2.2 release.
Since we focused mainly on supporting Intel devices, we dropped support for the
Gallium back end as Intel still uses the old DRI infrastructure. This decision,
however, also influenced the choice of the software rendering back end. Rather
than retaining the softpipe implementation, we now use swrast. In addition, we
changed the available OpenGL implementation from OpenGL ES 2.x to the fully
fledged OpenGL 4.5 profile, including the corresponding shader language
version. As with the previous Mesa port, EGL serves as front end API for
system integration and loads a DRI back-end driver (i965 or swrast). EGL
always requests the back-end driver 'egl_drv.lib.so' in form of a shared
object. Genode's relabeling features are used to select the proper back end
via a route configuration. The following snippet illustrates such a
configuration for software rendering:

! <start name="gears" caps="200">
!   <resource name="RAM" quantum="32M"/>"
!   <route>
!     <service name="ROM" label="egl_drv.lib.so">
!       <parent label="egl_swrast.lib.so"/>
!     </service>
!     <any-service> <parent/> <any-child/> </any-service>
!   </route>
! </start>

With the graphics-stack front end in place, it was time to take care of the
GPU driver. In our case this meant implementing the DRM interface in our
ported version of the Intel i915 DRM driver. Up to now, this driver was solely
used for mode setting while we completely omitted supporting the render
engine.

[image mesa_genode]

With this new and adapted software stack, we successfully could play ioquake3
on top of Genode with a reasonable performance in 1080p on a Thinkpad X250.

During this work, we gathered valuable insights into the architecture of a
modern 3D-graphics software stack as well as into recent Intel HD Graphics
hardware. We found that the Intel-specific Mesa driver itself is far more
complex than its kernel counter part. The DRM driver is mainly concerned with
resource and execution management whereas the Mesa driver programs the GPU.
For example, amongst others, Mesa compiles the OpenGL shaders into a
GPU-specific machine code that is passed on to the kernel for execution.

While inspecting the DRM driver, it became obvious that one of the reasons for
its complexity is the need to support a variety of different HD Graphics
generations as well as different features driven by software-usage patterns.
For our security related use cases, it is important to offer a clear isolation
and separation mechanism per client. Hardware features provided by modern
Intel GPUs like per-process graphics translation tables (PPGTT) and hardware
contexts that are unique for each client make it possible to fulfill these
requirements.

By focusing on this particular feature set and thus limiting the supported
hardware generations, the development of a maintainable GPU multiplexer for
Genode became feasible. After all, we strive to keep all Genode components as
low complex as possible, especially resource multiplexers like such a GPU
multiplexer.

[image intel_gpu_drv]
  This image shows multiple GPU-session clients and the resources they are
  using. The fence registers as well as the aperture is partitioned between
  them, the PPGTT is backed by the system memory, and the contexts are located
  in disjoint GGTT regions.

Within four months, we implemented an experimental GPU multiplexer for Intel
HD Graphics Gen8 (Broadwell class) devices. We started out defining a GPU
session interface that is sufficient to implement the API used by the DRM
library. For each session, the driver creates a context consisting of a
hardware context, a set of page tables (PPGTT), and a part of the aperture.
The client may use the session to allocate and map memory buffers used by the
GPU. Each buffer is always eagerly mapped 1:1 into the PPGTT by using the
local virtual address of the client. Special memory buffers like an image
buffer are additionally mapped through the aperture to make use of the
hardware-provided de-tiling mechanism. As is essential in Genode components,
the client must donate all resources that the driver might need to fulfill the
request, i.e., quota for memory and capability allocations. Clients may
request the execution of their workload by submitting an execution buffer. The
GPU multiplexer will then enqueue the request and schedule all pending
requests sequentially. Once the request is completed, the client is notified
via a completion signal.

[image multi_gl]
  Example scenario of multiple OpenGL programs that use the new GPU multiplexer
  for hardware-accelerated rendering.

We consider this first version of the GPU driver as experimental. As of now,
it only manages the render engine of the GPU. Mode-setting or rather display
handling must be performed by another component. Currently, the VESA driver is
used for this purpose. It also lacks any power-management functionality and
permanently keeps the GPU awake. Both limitations will be addressed in future
releases and support for Gen9+ (Skylake) and newer devices might be added.

In its current incarnation, the GPU multiplexer component consists of about
4,200 lines of code whereas the Mesa DRI i965 driver complements the driver at
the client side with about 78,000 lines of code.


The seL4 kernel on ARM and 64-bit x86 hardware
##############################################

With the 16.08 release, we brought the seL4 support to a level to be
considered being on par with the other supported kernels. At the time,
Genode's use of seL4 was limited to 32-bit x86 platforms.

In the current release, we extend the platform support to ARM and 64-bit x86.
We started this line of work with an incremental kernel upgrade from version
3.2.0 to 5.2.0 and finally to seL4 6.0. Through these upgrades, we were able
to drop several Genode-specific seL4 patches, which were required in the 16.08
release. One major improvement of version 6.0 compared to earlier versions is
the handling of device-memory announcements by the kernel to Genode's roottask
_core_.

With the kernel update in place, we inspected the x86-specific part thoroughly
while splitting and separating it properly into architecture-agnostic and
architecture-dependent parts. Upon this work, we added the
architecture-specific counterparts for x86_64 and ARM. One major work item was
to make the page-table handling in Genode's core aware and generic enough to
handle the different page-table sizes of the three architectures.

For the ARM support, we decided to enable the i.MX6 FreeScale based SoC,
namely the Wandboard Quad board. Since the seL4 kernel interface provides no
timeout support, we revived a user-level timer driver that we originally
developed for our custom base-hw kernel: The so-called EPIT timer, which is
part of most i.MX SoCs.

We finished the essential work for the mentioned three platforms in
less time than expected and, thereby, had spare time to address additional
features.

First, we enabled multiprocessor support for Genode/seL4 on x86 and
thread-priority support for all seL4 platforms. Additionally, we were able to
utilize the seL4 benchmark interface for Genode's trace infrastructure in
order to obtain utilization information about threads and CPUs. The Genode
components _top_ (text-based) and _cpu_load_monitor_ (graphical) are now
usable on Genode/seL4.
Finally, as we are currently exploring the support for booting various kernels
via UEFI on x86, we took the chance to investigate the steps needed to boot
seL4 via UEFI. UEFI firmware does not always provide a compatibility support
module (CSM) for legacy BIOS boot support. Hence, we extended the seL4 kernel
for Genode according to the Multiboot2 specification, which enables us to
start Genode/seL4 together with GRUB2 - as an UEFI capable bootloader - on
machines missing CSM support.


Base framework and OS-level infrastructure
##########################################

Simplified IOMMU handling
=========================

When IOMMUs are used on x86, all host memory targeted via direct memory
accesses (DMA) by devices must eagerly be registered in the respective I/O
page table of the device. Up to now, Genode supports IOMMUs on NOVA only. On
this kernel, a device protection domain is represented as a regular protection
domain with its virtual memory layout being used for both the CPU's MMU and
the device. Traditionally, mappings into such virtual memory spaces are
inserted on demand as responses to page faults. However, as there are no page
faults for DMA transactions, DMA buffers must always be eagerly mapped. The
so-called device PD hid this gap for NOVA. In anticipation of adding IOMMU
support for more kernels, we desired to generalize the device-PD mechanism by
introducing an explicit way to trigger the insertion of DMA memory into the
proper page tables.

We extended the PD-session interface by a 'map' function, which takes a
virtual memory region of the PD's virtual address space as argument. The page
frames of the previously attached dataspaces are added eagerly by core to the
IOMMU page-tables. With this explicit 'map' support, we were able to replace
the Genode/NOVA-specific device-PD implementation with a generic one, which
will easily accommodate other kernels in the future.


New report server for capturing reports to files
================================================

The report session is a simple mechanism for components to publish structured
data without the complexity of a file-system layer. In the simplest case, a
client component will produce a report and communicate it directly to a
component acting as a server. The disadvantage is that the report client
becomes reliant on the liveliness and presence of the consumer component. So
in the more robust case, the _report_rom_ component acts as the server hosting
the report service as well as a ROM service for components consuming reports.

The _report_rom_ server permits ROM access only to clients matching an
explicit configuration policy. This is good for security but opaque to a user.
Reports can only be read where an explicit policy is in place and only a
single report session can report to an active ROM session.

The new _fs_report_ component is a friendlier and more flexible report server.
Reports are written to a file system using a file and directory hierarchy that
expresses session routing. This allows for intuitive report inspection and
injection via a file system. When used with the _ram_fs_ and _fs_rom_ servers,
it can also replicate the functionality of _report_rom_.


New runtime environment for starting components sequentially
============================================================

The _init_ component is a prime example of software with an emphasis on
function over features. It is the fundamental building block for combining
components yet its behavior is simple and without heuristics. Like other
contemporary init managers, it starts components in parallel, but to a more
extreme degree in that it has no concept of "runlevels" or "targets", all
components are started as soon as possible. The concrete sequence of execution
is instead determined by when server components make service announcements and
how quickly they respond to client requests.

In some cases, the execution of one component must not occur until the
execution of another component ends, be it that the first produces output that
is consumed by the second, or that the two contend for a service that cannot
be multiplexed. Init contains no provisions to enforce ordering. But we are
free to define new behaviors in other management components.

The solution to the problem of ordering is the _sequence_ component. Sequence
walks a list of children and executes them in order, one at a time. With only
one child active, there is no need for any local resource or routing
management. By applying the same session label transformations as init,
external routing and policy handling are unchanged.

An example of ordering a producer and consumer within an init configuration
follows:
! <start name="sequence">
!   <resource name="RAM" quantum="128M"/>
!   <config>
!     <start name="producer">
!       <config .. />
!     </start>
!     <start name="consumer">
!       <config .. />
!     </start>
!   </config>
!   <route>
!     <service name="LOG" label_prefix="producer">
!       <child name="log_a"/> </service>
!     <service name="LOG" label_prefix="consumer">
!       <child name="log_b"/> </service>
!     <any-service> <parent/> <any-child/> </any-service>
!   </route>
! </start>


Support for boot-time initialized frame buffer
==============================================

UEFI-based systems do not carry along legacy BIOS infrastructure, on which
our generic VESA driver depends. Hence, when booting via UEFI, one has to use
either a hardware-specific driver like our Intel-FB driver or - alternatively -
facilitate generic UEFI mechanisms.

Instead of booting in VGA text mode and leaving the switch to a graphics mode
(via real-mode SVGA BIOS subroutines) to the booted OS, UEFI employs the
so-called graphics output protocol as a means to setup a reasonable default
graphics mode prior booting the operating system. In order to produce
graphical output, the operating system merely has to know the physical address
and layout of the frame buffer. Genode's core exposes this information as the
_platform_info_ ROM module. The new _fb_boot_drv_ driver picks up this
information to provide a Genode framebuffer session interface. Hence, on
UEFI-based systems, it can be used as a drop-in replacement for the VESA
driver. In contrast to the VESA driver, however, it is not able to switch
graphics modes at runtime.

The new component is located at _os/src/drivers/framebuffer/boot/_. Thanks
to Johannes Kliemann for this contribution.


Extended non-blocking operation of the VFS
==========================================

In
[https://genode.org/documentation/release-notes/17.02#VFS_support_for_asynchronous_I_O_and_reconfiguration - version 17.02],
we added support for non-blocking reads from the VFS in the form of the
'read_ready()', 'queue_read()', and 'complete_read()' functions. Since then,
it has become obvious that blocking within the VFS is not only problematic in
the VFS server itself when multiple clients are connected, but also when the
VFS is deployed in a multi-threaded environment and a VFS plugin needs to
reliably wait for I/O-completion signals.

For this reason, we reworked the interface of the VFS even more towards
non-blocking operation and adapted the existing users of the VFS accordingly.

The most important changes are:

* Directories are now created and opened with the 'opendir()' function and
  the directory entries are read with the 'queue_read()' and 'complete_read()'
  functions.

* Symbolic links are now created and opened with the 'openlink()' function and
  the link target is read with the 'queue_read()' and 'complete_read()'
  functions and written with the 'write()' function.

* The 'write()' function does not wait for signals anymore. This can have the
  effect that data written by a VFS library user has not been processed by a
  file-system server when the library user asks for the size of the file or
  closes it (both done with RPC functions at the file-system server). For this
  reason, a user of the VFS library should request synchronization before
  calling 'stat()' or 'close()'. To make sure that a file-system server has
  processed all write request packets that a client submitted prior the
  synchronization request, synchronization is now requested at the file-system
  server with a synchronization packet instead of an RPC function. Because of
  this change, the synchronization interface of the VFS library has been split
  into the 'queue_sync()' and 'complete_sync()' functions.


Making block sessions read-only by default
==========================================

Genode server components are expected to apply the safest and strictest
behavior when exposing cross-component state or persistent data. In practice
block and file-system servers only allow access to clients with explicitly
configured local policies. The file-system servers enforce an additional
provision that sessions are implicitly read-only unless overridden by policy.
This release introduces a similar restriction to the AHCI driver and partition
multiplexer. Clients of these servers require an affirmative 'writeable'
attribute on policies to permit the writing of blocks. Write permission at
these servers may also be revoked by components that forward block-session
requests by placing 'writeable="no"' into session-request arguments.

All users of _ahci_drv_ and _part_blk_ are advised that this change may break
existing configurations without explicit 'writeable' policies.


Refined time handling
=====================

Release 17.05 introduced a
[https://genode.org/documentation/release-notes/17.05#New_API_for_user-level_timing - new API for user-level timing]
named _timeout framework_. Together with this new framework came a
comprehensive test that stresses all aspects of the interface. During the past
few months, this test has turned out to be an enrichment for Genode far beyond
its original scope. As the test significantly raised the standards in
user-level timing, it also sharpened our view on the measurement precision of
various timer drivers and timestamps, which act as input for the framework.
This revealed several problems previously unidentified. For instance, we
improved the accuracy and stability of the time values provided by the drivers
for the Raspberry-Pi timer, the Cortex-A9 timer, the PIT, and the LAPIC. We
also were able to further optimize the calibration of the TSC in the NOVA
kernel.

Additionally, the test also helped us to refine the timeout framework itself.
The initial calibration of the framework - that previously took about 1.5
seconds - is now performed much quicker. This makes microseconds-precise time
available immediately after the timer connection switched to the modern
fine-grained mode of operation, which is a prerequisite for hardware drivers
that need such precision during their early initialization phase. The
calculations inside the framework also became more flexible to better fit the
characteristics of all the hardware and kernels Genode supports.

Finally, we were able to extend the application of the timeout framework. Most
notably, our C runtime uses it as timing source to the benefit of all
libc-using components. Another noteworthy case is the USB driver on the
Raspberry Pi. It previously couldn't rely on the default Genode timing but
required a local hardware timer to reach the precision that the host
controller expected from software. With the timeout framework, this workaround
could be removed from the driver.


FatFS-based VFS plugin
======================

Genode has supported VFAT file-systems since the 9.11 release when the
[http://elm-chan.org/fsw/ff/00index_e.html - FatFS] library was first ported.
The 11.08 release fit the library into the libc plugin architecture and
in 12.08 FatFS was used in the _ffat_fs_ file-system server. Now, the 17.08
release revisits FatFS to mold the library into the newer and more flexible
VFS plugin system. The _vfs_fatfs_ plugin may be fitted into the VFS server or
used directly by arbitrary components linked to the VFS library. As the
collection of VFS plugins in combination with the VFS file-system server has a
lower net maintenance cost than multiple file-system servers, the _ffat_fs_
server will be retired in a future release.


Enhanced GUI primitives
=======================

Even though we consider Qt5 as the go-to solution for creating advanced
graphical user interfaces on top of Genode, we also continue to explore an
alternative approach that facilitates Genode's component architecture to an
extreme degree. The so-called menu-view component takes an XML description of
a dialog as input and produces rendered pixels as output. It also gives
feedback to user input such as the hovered widget at a given pointer position.
The menu view does not implement any application logic but is meant to be
embedded as a child component into the actual application. This approach
relieves the application from the complexity (and potential bugs) of widget
rendering. It also reinforces a rigid separation of a view and its underlying
data model.

The menu view was first introduced in
[https://genode.org/documentation/release-notes/14.11#New_menu_view_application - version 14.11].
The current release improves it in the following ways:

* The new '<float>' widget aligns a child widget within a
  larger parent widget by specifying the boolean attributes 'north', 'south',
  'east', and 'west'. If none is specified, the child is centered. If opposite
  attributes are specified, the child is stretched.

* A new '<depgraph>' widget arranges child widgets in the form of a
  dependency graph, which will be the cornerstone for Genode's upcoming
  interactive component-composition feature. As a prerequisite for
  implementing the depgraph widget, Genode's set of basic graphical primitives
  received new operations for drawing sub-pixel-accurate anti-aliased lines
  and bezier curves.

* All geometric changes of the widget layout are animated now. This includes
  structural changes of the new '<depgraph>' widget.

[image depgraph]

The menu-view component is illustrated by the run script at
_gems/run/menu_view.run_.


C runtime
=========

The growing number of ported applications used on Genode is accompanied by the
requirement of extensive POSIX compatibility of our C runtime. Therefore, we
enhanced our implementation by half a dozen features (e.g., O_ACCMODE
tracking) during the past release cycle. We thank the contributors of patches
and test cases and will continue our efforts to accommodate more ported
open-source components in the future.


Libraries and applications
##########################

Mesa adjustments
================

The Mesa update required the adaption of all components that use OpenGL.
In particular that means the Qt5 framework. Furthermore, we also enabled
OpenGL support in our SDL1 port.

As playground, there are a few OpenGL examples. The demos are located under
_repos/libports/src/test/mesa_demos_, which use the EGLUT bindings. There
are also some SDL based examples in the world repository under
_repos/world/src/test/sdl_opengl_.


Package management
==================

The previous release featured the initial version of Genode's
[https://genode.org/documentation/release-notes/17.05#Package_management - custom package-management tools].
Since then, we continued this line of work in three directions.

First, we refined the depot tools and the integration of the depot with our
custom work-flow ("run") tool. One important refinement is a simplification of
the depot's directory layout for library binaries. We found that the initial
version implied unwelcome complexities down the road. Instead of placing
library binaries in a directory named after their API, they are now placed
directly in the architecture directory along with regular binaries.

Second, driven by the proliferated use of the depot by more and more run
scripts, we enhanced the depot with new depot recipes as needed.

Third, we took the first steps to use the depot on-target. The experimentation
with on-target depots is eased by the new 'create_tar_from_depot_binaries'
function of the run tool, which allows one to assemble a new depot in the form
of a tar archive out of a subset of packages. Furthermore, the new
_depot_query_ component is able to scan an on-target depot for runtime
descriptions and returns all the information needed to start a subsystem based
on the depot content. The concept is exemplified by the new
_gems/run/depot_deploy.run_ script, which executes the "fs_report" test case
supplied via a depot package.


Platforms
#########

Genode as Xen DomU
==================

We want to widen the application scope of Genode by enabling users to easily
deploy Genode scenarios on Xen-based cloud platforms.

As a first step towards this goal, we enhanced our run tool to support running
Genode scenarios as a local Xen DomU, managed from within the Genode build
system on Linux running as Xen Dom0.

The Xen DomU runs in HVM mode (full virtualization) and loads Genode from an
ISO image. Serial log output is printed to the text console and graphical
output is shown in an SDL window.

To use this new target platform, the following run options should be defined in
the 'build/x86_*/etc/build.conf' file:

! RUN_OPT  = --include boot_dir/$(KERNEL)
! RUN_OPT += --include image/iso
! RUN_OPT += --include power_on/xen
! RUN_OPT += --include log/xen
! RUN_OPT += --include power_off/xen

The Xen DomU is managed using the 'xl' command line tool and it is possible to
add configuration options in the 'xen_args' variable of a run script. Common
options are:

* Disabling the graphical output:

  ! append xen_args { sdl="0" }

* Configuring a network device:

  ! append xen_args { vif=\["model=e1000,mac=02:00:00:00:01:01,bridge=xenbr0"\] }

* Configuring USB input devices:

  ! append xen_args { usbdevice=\["mouse","keyboard"\] }

Note that the 'xl' tool requires super-user permissions. Interactive
password input can be complicated in combination with 'expect' and is not
practical for automated tests. For this reason, the current implementation
assumes that no password input is needed when running 'sudo xl', which can
be achieved by creating a file '/etc/sudoers.d/xl' with the content

! user ALL=(root) NOPASSWD: /usr/sbin/xl

where 'user' is the Linux user name.


Execution on bare hardware (base-hw)
====================================

UEFI support
------------

Analogously to our work on the seL4 and NOVA kernels in this release, we
extended our base-hw kernel to become a Multiboot2 compliant kernel. When used
together with GRUB2, it can be started on x86 UEFI machines missing legacy
BIOS support (i.e., CSM).


RISC-V
------

With Genode version 17.05, we updated base-hw's RISC-V support to privileged
ISA revision 1.9.1. Unfortunately, this implied that dynamic linking was not
supported on the RISC-V architecture anymore. Since dynamic linking is now
required for almost all Genode applications by default, this became a severe
limitation. Therefore, we revisited our RISC-V implementation - in particular
the kernel entry code - to lift the limitation of being able to execute only
statically linked binaries.

Additionally, we integrated the Berkeley Boot Loader (BBL), which bootstraps
the system and implements the machine mode, more closely into our build
infrastructure. We also added a new timer implementation to base-hw by using
the _set timeout SBI_ call of BBL.

What still remains missing is proper FPU support. While we are building the
Genode tool chain with soft float support, we still encounter occasions where
FPU code is generated, which in turn triggers compile time errors. We will
have to investigate this behavior more thoroughly, but ultimately we want to
add FPU support for RISC-V to our kernel and enable hardware floating point in
the tool chain.


Muen separation kernel
======================

Besides updating the Muen port to the latest kernel version as of end of June,
Muen has been added to Genode's automated testing infrastructure. This
includes the revived support for VirtualBox 4 on top of this kernel.


NOVA microhypervisor
====================

The current release extends NOVA to become a Multiboot2 compliant kernel. Used
together with GRUB2, NOVA can now be started on x86 UEFI machines missing
legacy BIOS support (called CSM).

GRUB2 provides the initial ACPI RSDP (Root System Description Pointer) to a
Multiboot2 kernel. The RSDP contains vital information required to bootstrap
the kernel and the operating system in general on today's x86 machines. To
make this information available to the user-level ACPI and ACPICA drivers, the
kernel propagates the RSDP to Genode's core, which - in turn - exposes it to
the user land as part of the _platform_info_ ROM module.

In order to ease the setup of an UEFI bootable image, we added a new image
module to our run-tool infrastructure. The run option 'image/uefi' can be used
instead of 'image/iso' in order to create a raw image that contains a EFI
system partition in a GUID partition table (GPT). The image is equipped by the
new 'image/uefi' module with the GRUB2 boot loader, a GRUB2 configuration, and
the corresponding Genode run scenario. The final image can be copied with 'dd'
to a bootable USB stick. Additionally, we added support to boot such an image
on Qemu leveraging [https://www.tianocore.org - TianoCore's] UEFI firmware.

As a side project, minor virtualization support for AMD has been added to
Virtualbox 4 and to the NOVA kernel on Genode. This enables us to run a 32-bit
Windows 7 VM on a 32-bit Genode/NOVA host on an (oldish) AMD Phenom II X4 test
machine.