Piotr Tworek 643747b912 os: Refactor VirtIO::Queue implementation.
The key changes in this patch are:
* Buffer allocation is moved into a separate Buffer_pool helper. The
  implementation of the buffer allocation strategy does not change.
  The helper allocates a single RAM dataspace and splits it in multiple,
  equally sized chunks.
* Management of main descriptor ring is enacapsulated in Descriptor_ring
  helper class.
* Use separate RAM dataspaces for descriptor rings and buffers.
  Previously both of them were packed into a single dataspace. This
  might have been more RAM efficient, but IMO it made the code uglier and
  harder to understand.
* All of the VirtIO::Queue members are now initialized on the class member
  initializer list. This is possible due to previously listed changes.
* Since all VirtIO::Queue members are initalized on member initalizer
  list, some additional ones can be marked as const, ex _avail, _used ring
  pointers.
* Move descriptor writing code into a common method used by both
  write_data and write_data_read_reply members. This avoids some code
  duplication between those methods.
* Get rid of request_irq argument that most public VirtIO::Queue methods
  accept. None of the existing drivers use it and I doubt this will
  change any time soon.
* Use Genode namespace by default in Virtio.

This patch also fixes at least one bug that I discovered while working
on VirtIO block device driver. Namely, when chaining descriptors only the
first descriptor in the chain should be exposed in the available ring.

Issue #4347
2021-12-17 15:04:48 +01:00
2021-11-30 14:32:17 +01:00
2020-03-26 11:38:54 +01:00
2021-11-30 14:34:09 +01:00

                      =================================
                      Genode Operating System Framework
                      =================================


This is the source tree of the reference implementation of the Genode OS
architecture. For a general overview about the architecture, please refer to
the project's official website:

:Official project website for the Genode OS Framework:

  [https://genode.org/documentation/general-overview]

The current implementation can be compiled for 8 different kernels: Linux,
L4ka::Pistachio, L4/Fiasco, OKL4, NOVA, Fiasco.OC, seL4, and a custom
kernel for running Genode directly on ARM-based hardware. Whereas the Linux
version serves us as development vehicle and enables us to rapidly develop the
generic parts of the system, the actual target platforms of the framework are
microkernels. There is no "perfect" microkernel - and neither should there be
one. If a microkernel pretended to be fit for all use cases, it wouldn't be
"micro". Hence, all microkernels differ in terms of their respective features,
complexity, and supported hardware architectures.

Genode allows the use of each of the kernels listed above with a rich set of
device drivers, protocol stacks, libraries, and applications in a uniform way.
For developers, the framework provides an easy way to target multiple different
kernels instead of tying the development to a particular kernel technology. For
kernel developers, Genode contributes advanced workloads, stress-testing their
kernel, and enabling a variety of application use cases that would not be
possible otherwise. For users and system integrators, it enables the choice of
the kernel that fits best with the requirements at hand for the particular
usage scenario.


Documentation
#############

The primary documentation is the book "Genode Foundations", which is available
on the front page of Genode website:

:Download the book "Genode Foundations":

  [https://genode.org]

The book describes Genode in a holistic and comprehensive way. It equips you
with a thorough understanding of the architecture, assists developers with the
explanation of the development environment and system configuration, and
provides a look under the hood of the framework. Furthermore, it contains the
specification of the framework's programming interface.

The project has a quarterly release cycle. Each version is accompanied with
detailed release documentation, which is available at the documentation
section of the project website:

:Release documentation:

  [https://genode.org/documentation/release-notes/]


Directory overview
##################

The source tree is composed of the following subdirectories:

:'doc':

  This directory contains general documentation along with a comprehensive
  collection of release notes.

:'repos':

  This directory contains the source code, organized in so-called source-code
  repositories. Please refer to the README file in the 'repos' directory to
  learn more about the roles of the individual repositories.

:'tool':

  Source-code management tools and scripts. Please refer to the README file
  contained in the directory.

:'depot':

  Directory used by Genode's package-management tools. It contains the public
  keys and download locations of software providers.


Additional community-maintained components
##########################################

The components found within the main source tree are complemented by a growing
library of additional software, which can be seamlessly integrated into Genode
system scenarios.

:Genode-world repository:

  [https://github.com/genodelabs/genode-world]


Contact
#######

The best way to get in touch with Genode developers and users is the project's
mailing list. Please feel welcome to join in!

:Genode Mailing Lists:

  [https://genode.org/community/mailing-lists]


Commercial support
##################

The driving force behind the Genode OS Framework is the German company Genode
Labs. The company offers commercial licensing, trainings, support, and
contracted development work:

:Genode Labs website:

  [https://www.genode-labs.com]

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