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| -rw-r--r-- | introduction.tex | 27 |
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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 diff --git a/introduction.tex b/introduction.tex index 4ea4259..65392d9 100644 --- a/introduction.tex +++ b/introduction.tex @@ -38,6 +38,33 @@ between different transports. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in \hyperref[intro:rfc2119]{[RFC2119]}. +An older specification (see \hyperref[intro:Virtio PCI Draft]{[Virtio PCI Draft]}) defined a +similar, but different interface between the hypervisor and the guest. +To simplify transition and note differences, the following terms are used: + +\begin{description} +\item[Legacy Interface] + An interface specified by \hyperref[intro:Virtio PCI Draft]{[Virtio PCI Draft]}. +\item[Legacy Device] + A device which implements \hyperref[intro:Virtio PCI Draft]{[Virtio PCI Draft]}, but not this specification. +\item[Legacy Driver] + A driver which implements \hyperref[intro:Virtio PCI Draft]{[Virtio PCI Draft]}, but not this specification. +\item[Transitional Device] + A device which implements both this specification and the older + \hyperref[intro:Virtio PCI Draft]{[Virtio PCI Draft]} + specification, thus allowing legacy drivers. +\item[Transitional Driver] + A device which implements both this specification and the older + \hyperref[intro:Virtio PCI Draft]{[Virtio PCI Draft]} + specification, thus allowing legacy devices. +\item[Non-Transitional Device] + A device which does not implement the + \hyperref[intro:Virtio PCI Draft]{[Virtio PCI Draft]} specification. +\item[Non-Transitional Driver] + A driver which does not implement the + \hyperref[intro:Virtio PCI Draft]{[Virtio PCI Draft]} specification. +\end{description} + \section{Normative References} \begin{longtable}{l p{5in}} |