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Subject: Re: [tab] Re: [virtio-comment] TAB Comments on Virtual I/O Device (VIRTIO) Version 1.0
Patrick Durusau <patrick@durusau.net> writes: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Michael, > > Just a thought, the legacy devices conform to some prior > specification. Yes? > > So it really isn't that transitional devices, which include legacy > plus the new standard conform only to the new standard but they do > conform to the new standard plus one or more old ones. > > One way to organize that in terms of conformance: > > 1) Non-Transition devices (here enumerate the requirements for a > non-transitional device and what happens if I do something optional, > what does someone on the other end have to accept?) Well, all that should be nailed down in the rest of the content. It says what drivers must do *and* what devices must do. This language has been repeatedly tightened during the 1.0 drafting process (and especially from recent feedback), so hopefully it's fairly robust now. > 2) Transitional devices - conform to all of #1, no reason to repeat, > and MAY conform to one or more legacy standards (include as normative > references) so you don't have to risk being at variance with the prior > work by repetition. Then your legacy material become > non-normative/informative, for the readers convenience and you > normatively cite the prior standards, to say: Go see the original if > you want to do X. > > Include rules in the normative text about what happens when > non-transitional and transitional devices meet. > > That may (or may not be) closer to what you originally intended in > making legacy material non-normative. That will allow old standards to > stand for themselves. A lot safer than way than trying to restate them. OK, how about simply this: diff --git a/conformance.tex b/conformance.tex index 0e8b321..e2dadb9 100644 --- a/conformance.tex +++ b/conformance.tex @@ -6,3 +6,46 @@ An implementation conforms to this specification if it satisfies all of the MUST or REQUIRED level requirements defined within this specification. + +An implementation MAY choose to implement support for legacy drivers +or devices, by conforming to \hyperref[intro:Virtio PCI Draft]{[Virtio PCI Draft]}. +The sections named "Legacy Interfaces" are non-normative, but should +be helpful for those wishing to support legacy drivers or devices: +\begin{itemize} +\item Section \ref{sec:Basic Facilities of a Virtio Device / Feature Bits / Legacy Interface: A Note on transitions from earlier drafts} +\item Section \ref{sec:Basic Facilities of a Virtio Device / Device Configuration Space / Legacy Interface: A Note on Configuration Space endian-ness} +\item Section \ref{sec:Basic Facilities of a Virtio Device / Device Configuration Space / Legacy Interface: Device Configuration Space} +\item Section \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Legacy Interfaces: A Note on Virtqueue Layout} +\item Section \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Legacy Interfaces: A Note on Virtqueue Endianness} +\item Section \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Message Framing / Legacy Interface: Message Framing} +\item Section \ref{sec:General Initialization And Device Operation / Device Initialization / Legacy Interface: Device Initialization} +\item Section \ref{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Discovery / Legacy Interfaces: A Note on PCI Device Discovery} +\item Section \ref{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Legacy Interfaces: A Note on PCI Device Layout} +\item Section \ref{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Device Initialization / Virtio Device Configuration Layout Detection / Legacy Interface: A Note on Device Layout Detection} +\item Section \ref{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Device Initialization / Virtqueue Configuration / Legacy Interface: A Note on Virtqueue Configuration} +\item Section \ref{sec:Virtio Transport Options / Virtio Over MMIO / Legacy interface} +\item Section \ref{sec:Virtio Transport Options / Virtio over channel I/O / Device Initialization / Setting the Virtio Revision / Legacy Interfaces: A Note on Setting the Virtio Revision} +\item Section \ref{sec:Virtio Transport Options / Virtio over channel I/O / Device Initialization / Configuring a Virtqueue / Legacy Interface: A Note on Configuring a Virtqueue} +\item Section \ref{sec:Virtio Transport Options / Virtio over channel I/O / Device Operation / Host->Guest Notification / Legacy Interfaces: A Note on Host->Guest Notification} +\item Section \ref{sec:Virtio Transport Options / Virtio over channel I/O / Device Initialization / Setting Up Indicators / Legacy Interfaces: A Note on Setting Up Indicators} +\item Section \ref{sec:Device Types / Network Device / Feature bits / Legacy Interface: Feature bits} +\item Section \ref{sec:Device Types / Network Device / Device configuration layout / Legacy Interface: Device configuration layout} +\item Section \ref{sec:Device Types / Network Device / Device Operation / Legacy Interface: Device Operation} +\item Section \ref{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Setting MAC Address Filtering / Legacy Interface: Setting MAC Address Filtering} +\item Section \ref{sec:Device Types / Network Device / Device Operation / Control Virtqueue / VLAN Filtering / Legacy Interface: VLAN Filtering} +\item Section \ref{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Automatic receive steering in multiqueue mode / Legacy Interface: Automatic receive steering in multiqueue mode} +\item Section \ref{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Offloads State Configuration / Setting Offloads State / Legacy Interface: Setting Offloads State} +\item Section \ref{sec:Device Types / Block Device / Feature bits / Legacy Interface: Feature bits} +\item Section \ref{sec:Device Types / Block Device / Feature bits / Device configuration layout / Legacy Interface: Device configuration layout} +\item Section \ref{sec:Device Types / Block Device / Device Initialization / Legacy Interface: Device Initialization} +\item Section \ref{sec:Device Types / Block Device / Device Operation / Legacy Interface: Device Operation} +\item Section \ref{sec:Device Types / Console Device / Device configuration layout / Legacy Interface: Device configuration layout} +\item Section \ref{sec:Device Types / Console Device / Device Operation / Legacy Interface: Device Operation} +\item Section \ref{sec:Device Types / Memory Balloon Device / Device configuration layout / Legacy Interface: Device configuration layout} +\item Section \ref{sec:Device Types / Memory Balloon Device / Device Operation / Memory Statistics / Legacy Interface: Memory Statistics} +\item Section \ref{sec:Device Types / SCSI Host Device / Device configuration layout / Legacy Interface: Device configuration layout} +\item Section \ref{sec:Device Types / SCSI Host Device / Device Operation / Device Operation: Request Queues / Legacy Interface: Device Operation: Request Queues} +\item Section \ref{sec:Device Types / SCSI Host Device / Device Operation / Device Operation: controlq / Legacy Interface: Device Operation: controlq} +\item Section \ref{sec:Device Types / SCSI Host Device / Device Operation / Device Operation: eventq / Legacy Interface: Device Operation: eventq} +\item Section \ref{sec:Reserved Feature Bits / Legacy Interface: Reserved Feature Bits} +\end{itemize} diff --git a/content.tex b/content.tex index a47ce6c..0e6c963 100644 --- a/content.tex +++ b/content.tex @@ -1288,6 +1288,20 @@ As a prerequisite to device initialization, the driver scans the PCI capability list, detecting virtio configuration layout using Virtio Structure PCI capabilities. +\paragraph{Non-transitional Device With Legacy Driver}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Device Initialization / Non-transitional Device With Legacy Driver} + +Non-transitional devices, on a platform where a legacy driver for +a legacy device with the same ID might have previously existed, +MUST take the following steps to fail gracefully when a legacy +driver attempts to drive them: + +\begin{enumerate} +\item Present an I/O BAR in BAR0, and +\item Respond to a single-byte zero write to offset 18 + (corresponding to Device Status register in the legacy layout) + of BAR0 by presenting zeroes on every BAR and ignoring writes. +\end{enumerate} + \subparagraph{Legacy Interface: A Note on Device Layout Detection}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Device Initialization / Virtio Device Configuration Layout Detection / Legacy Interface: A Note on Device Layout Detection} Legacy drivers skipped the Device Layout Detection step, assuming legacy @@ -1310,18 +1324,6 @@ Capabilities on the capability list. If these are not present, driver should assume a legacy device, and fail gracefully. -Non-transitional devices, on a platform where a legacy driver for -a legacy device with the same ID might have previously existed, -MUST take the following steps to fail gracefully when a legacy -driver attempts to drive them: - -\begin{enumerate} -\item Present an I/O BAR in BAR0, and -\item Respond to a single-byte zero write to offset 18 - (corresponding to Device Status register in the legacy layout) - of BAR0 by presenting zeroes on every BAR and ignoring writes. -\end{enumerate} - \paragraph{MSI-X Vector Configuration}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Device Initialization / MSI-X Vector Configuration} When MSI-X capability is present and enabled in the device diff --git a/introduction.tex b/introduction.tex index a1b4239..f0b6aee 100644 --- a/introduction.tex +++ b/introduction.tex @@ -51,6 +51,9 @@ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "S PCI Express Specifications \newline\url{http://www.pcisig.com/specifications/pciexpress/}, PCI-SIG\\ + \phantomsection\label{intro:Virtio PCI Draft}\textbf{[Virtio PCI Draft]} & + Virtio PCI Draft Specification + \newline\url{http://ozlabs.org/~rusty/virtio-spec/virtio-0.9.5.pdf}\\ \end{longtable} \section{Structure Specifications}
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