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generated by cgit v1.2.3 (git 2.25.1) at 2025-11-05 22:33:09 +0000
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Diffstat
-rw-r--r--content.tex109
-rw-r--r--notifications-be.c5
-rw-r--r--notifications-le.c5
3 files changed, 6 insertions, 113 deletions
diff --git a/content.tex b/content.tex
index ae5fa4c..7a92cb1 100644
--- a/content.tex
+++ b/content.tex
@@ -283,49 +283,9 @@ Packed Virtqueues}).
Every driver and device supports either the Packed or the Split
Virtqueue format, or both.
-\subsection{Driver notifications} \label{sec:Virtqueues / Driver notifications}
-The driver is sometimes required to notify the device after
-making changes to the virtqueue.
-
-When VIRTIO_F_NOTIFICATION_DATA has not been negotiated,
-this notification involves sending the
-virtqueue number to the device (method depending on the transport).
-
-However, some devices benefit from the ability to find out the number of
-available descriptors in the ring without accessing the virtqueue in memory:
-for efficiency or as a debugging aid.
-
-To help with these optimizations, when VIRTIO_F_NOTIFICATION_DATA
-has been negotiated, driver notifications to the device include
-the following information:
-
-\begin{description}
-\item [VQ number]
-\item [Offset]
- Within the ring where the next available ring entry
- will be written.
- Without VIRTIO_F_RING_PACKED this refers to the
- 15 least significant bits of the available index.
- With VIRTIO_F_RING_PACKED this refers to the offset
- (in units of descriptor entries)
- within the descriptor ring where the next available
- descriptor will be written.
-\item [Wrap Counter]
- With VIRTIO_F_RING_PACKED this is the wrap counter
- referring to the next available descriptor.
- Without VIRTIO_F_RING_PACKED this is the most significant bit
- of the available index.
-\end{description}
-
-Note that the driver can trigger multiple notifications even without
-making any more changes to the ring. When VIRTIO_F_NOTIFICATION_DATA
-has been negotiated, these notifications would then have
-identical \field{Offset} and \field{Wrap Counter} values.
-
\input{split-ring.tex}
\input{packed-ring.tex}
-
\chapter{General Initialization And Device Operation}\label{sec:General Initialization And Device Operation}
We start with an overview of device initialization, then expand on the
@@ -902,9 +862,7 @@ the same Queue Notify address for all queues.
\devicenormative{\paragraph}{Notification capability}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Notification capability}
The device MUST present at least one notification capability.
-For devices not offering VIRTIO_F_NOTIFICATION_DATA:
-
-The \field{cap.offset} MUST be 2-byte aligned.
+The \field{cap.offset} MUST be 2-byte aligned.
The device MUST either present \field{notify_off_multiplier} as an even power of 2,
or present \field{notify_off_multiplier} as 0.
@@ -918,23 +876,6 @@ For all queues, the value \field{cap.length} presented by the device MUST satisf
cap.length >= queue_notify_off * notify_off_multiplier + 2
\end{lstlisting}
-For devices offering VIRTIO_F_NOTIFICATION_DATA:
-
-The device MUST either present \field{notify_off_multiplier} as a
-number that is a power of 2 that is also a multiple 4,
-or present \field{notify_off_multiplier} as 0.
-
-The \field{cap.offset} MUST be 4-byte aligned.
-
-The value \field{cap.length} presented by the device MUST be at least 4
-and MUST be large enough to support queue notification offsets
-for all supported queues in all possible configurations.
-
-For all queues, the value \field{cap.length} presented by the device MUST satisfy:
-\begin{lstlisting}
-cap.length >= queue_notify_off * notify_off_multiplier + 4
-\end{lstlisting}
-
\subsubsection{ISR status capability}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / ISR status capability}
The VIRTIO_PCI_CAP_ISR_CFG capability
@@ -1327,21 +1268,8 @@ separate cache lines.
\subsubsection{Notifying The Device}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Notifying The Device}
-When VIRTIO_F_NOTIFICATION_DATA has not been negotiated,
-the driver notifies the device by writing the 16-bit virtqueue index
-of this virtqueue (in little-endian byte order format)
-to the Queue Notify address.
-
-When VIRTIO_F_NOTIFICATION_DATA has been negotiated,
-the driver notifies the device by writing the following
-32-bit value to the Queue Notify address:
-\lstinputlisting{notifications-le.c}
-
-See \ref{sec:Virtqueues / Driver notifications}~\nameref{sec:Virtqueues / Driver notifications}
-for the definition of the components.
-
-See \ref{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Notification capability} for how to calculate the
-Queue Notify address.
+The driver notifies the device by writing the 16-bit virtqueue index
+of this virtqueue to the Queue Notify address. See \ref{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Notification capability} for how to calculate this address.
\subsubsection{Virtqueue Interrupts From The Device}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Virtqueue Interrupts From The Device}
@@ -1572,19 +1500,8 @@ All register values are organized as Little Endian.
}
\hline
\mmioreg{QueueNotify}{Queue notifier}{0x050}{W}{%
- Writing a value this register notifies the device that
- there are new buffers to process in a queue.
-
- When VIRTIO_F_NOTIFICATION_DATA has not been negotiated,
- the value written is the queue index.
-
- When VIRTIO_F_NOTIFICATION_DATA has been negotiated,
- the value has the following format:
-
- \lstinputlisting{notifications-le.c}
-
- See \ref{sec:Virtqueues / Driver notifications}~\nameref{sec:Virtqueues / Driver notifications}
- for the definition of the components.
+ Writing a queue index to this register notifies the device that
+ there are new buffers to process in the queue.
}
\hline
\mmioreg{InterruptStatus}{Interrupt status}{0x60}{R}{%
@@ -2423,22 +2340,12 @@ GPR & Input Value & Output Value \\
\hline
2 & Subchannel ID & Host Cookie \\
\hline
- 3 & Notification data & \\
+ 3 & Virtqueue number & \\
\hline
4 & Host Cookie & \\
\hline
\end{tabular}
-When VIRTIO_F_NOTIFICATION_DATA has not been negotiated,
-the \field{Notification data} contains the Virtqueue number.
-
-When VIRTIO_F_NOTIFICATION_DATA has been negotiated,
-the value has the following format:
-\lstinputlisting{notifications-be.c}
-
-See \ref{sec:Virtqueues / Driver notifications}~\nameref{sec:Virtqueues / Driver notifications}
-for the definition of the components.
-
\devicenormative{\paragraph}{Guest->Host Notification}{Virtio Transport Options / Virtio over channel I/O / Device Operation / Guest->Host Notification}
The device MUST ignore bits 0-31 (counting from the left) of GPR2.
This aligns passing the subchannel ID with the way it is passed
@@ -5441,10 +5348,6 @@ Descriptors} and \ref{sec:Packed Virtqueues / Indirect Flag: Scatter-Gather Supp
\item[VIRTIO_F_IN_ORDER(35)] This feature indicates
that all buffers are used by the device in the same
order in which they have been made available.
- \item[VIRTIO_F_NOTIFICATION_DATA(36)] This feature indicates
- that drivers pass extra data (besides identifying the Virtqueue)
- in their device notifications.
- See \ref{sec:Virtqueues / Driver notifications}~\nameref{sec:Virtqueues / Driver notifications}.
\end{description}
\drivernormative{\section}{Reserved Feature Bits}{Reserved Feature Bits}
diff --git a/notifications-be.c b/notifications-be.c
deleted file mode 100644
index 5be947e..0000000
--- a/notifications-be.c
+++ /dev/null
@@ -1,5 +0,0 @@
-be32 {
- vqn : 16;
- next_off : 15;
- next_wrap : 1;
-};
diff --git a/notifications-le.c b/notifications-le.c
deleted file mode 100644
index fe51267..0000000
--- a/notifications-le.c
+++ /dev/null
@@ -1,5 +0,0 @@
-le32 {
- vqn : 16;
- next_off : 15;
- next_wrap : 1;
-};
generated by cgit v1.2.3 (git 2.25.1) at 2025-11-05 22:33:09 +0000