[PATCH 14/14] non-transitional devices with legacy drivers

["Michael S. Tsirkin" <mst@redhat.com>]

weaken hacky requirements helpful for graceful failure
for non transitional PCI devices from MUST to SHOULD.
It's nice to have but it's not like it makes things work, and you
can avoid trouble simply by using the most recent drivers.
also move them out to a separate section
---
 content.tex | 34 +++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/content.tex b/content.tex
index d2de590..bc85350 100644
--- a/content.tex
+++ b/content.tex
@@ -880,7 +880,10 @@ is to allow devices to be versioned without breaking drivers.
 Transitional devices MUST have a Revision ID of 0 to match
 legacy drivers.
 
-Non-transitional devices MUST have a Revision ID of 1 or higher.
+Non-transitional devices SHOULD have a Revision ID of 1 or higher.
+
+This is to reduce the chance of a legacy driver attempting
+to drive the device.
 
 Both transitional and non-transitional drivers MUST match
 any Revision ID value.
@@ -1339,6 +1342,23 @@ see \ref{sec:Basic Facilities of a Virtio Device / Device
 Configuration Space / Legacy Interface: Device Configuration
 Space}~\nameref{sec:Basic Facilities of a Virtio Device / Device Configuration Space / Legacy Interface: Device Configuration Space} for workarounds.
 
+\subsubsection{Non-transitional Device With Legacy Driver: A Note
+on PCI Device Layout}\label{sec:Virtio Transport Options / Virtio
+Over PCI Bus / PCI Device Layout / Non-transitional Device With
+Legacy Driver: A Note on PCI Device Layout}
+
+Non-transitional devices, on a platform where a legacy driver for
+a legacy device with the same ID might have previously existed,
+SHOULD 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}
+
 \subsection{PCI-specific Initialization And Device Operation}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation}
 
 \subsubsection{Device Initialization}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Device Initialization}
@@ -1377,18 +1397,6 @@ Capabilities on the capability list.
 If these are not present, driver MUST 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
-- 
MST