diff options
Diffstat (limited to 'content.tex')
| -rw-r--r-- | content.tex | 50 |
1 files changed, 8 insertions, 42 deletions
diff --git a/content.tex b/content.tex index be9f176..cb090dd 100644 --- a/content.tex +++ b/content.tex @@ -88,45 +88,15 @@ space. \subsection{Legacy Interface: A Note on transitions from earlier drafts}\label{sec:Basic Facilities of a Virtio Device / Feature Bits / Legacy Interface: A Note on transitions from earlier drafts} -Earlier drafts of this specification (up to 0.9.X) defined a similar, but -different interface between the hypervisor and the guest. -Since these are widely deployed, this specification -accommodates optional features to simplify transition -from these earlier draft interfaces. Specifically: +Careful consideration has been given on the transition from the older +\hyperref[intro:Virtio PCI Draft]{[Virtio PCI Draft]} specification to +this one. Advice pertaining to transitional devices and drivers +is contained in sections named 'Legacy Interface' like this one. -\begin{description} -\item[Legacy Interface] - is an interface specified by an earlier draft of this specification - (up to 0.9.X) -\item[Legacy Device] - is a device implemented before this specification was released, - and implementing a legacy interface on the host side -\item[Legacy Driver] - is a driver implemented before this specification was released, - and implementing a legacy interface on the guest side -\end{description} - -Legacy devices and legacy drivers are not compliant with this -specification. - -To simplify transition from these earlier draft interfaces, -it is possible to implement: - -\begin{description} -\item[Transitional Device] - a device supporting both drivers conforming to this - specification, and allowing legacy drivers. - -\item[Transitional Driver] - a driver supporting both devices conforming to this - specification, and legacy devices. -\end{description} - -Transitional devices and transitional drivers can be compliant with -this specification (ie. when not operating in legacy mode). - -Devices or drivers with no legacy compatibility are referred to as -non-transitional devices and drivers, respectively. +\begin{note} + No legacy interfaces are required; ie. don't implement them unless you + have a need for backwards compatibility! +\end{note} Transitional Drivers can detect Legacy Devices by detecting that the feature bit VIRTIO_F_VERSION_1 is not offered. @@ -134,10 +104,6 @@ Transitional devices can detect Legacy drivers by detecting that VIRTIO_F_VERSION_1 has not been acknowledged by the driver. In this case device is used through the legacy interface. -To make them easier to locate, specification sections documenting -these transitional features are explicitly marked with 'Legacy -Interface' in the section title. - \section{Device Configuration Space}\label{sec:Basic Facilities of a Virtio Device / Device Configuration Space} Device configuration space is generally used for rarely-changing or |