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Subject[virtio-dev] [PATCH v2 2/5] virtio-mmio: Enhance queue notification support
Date
With VIRTIO_F_MMIO_NOTIFICATION feature bit offered, the notification
mechanism is enhanced. Driver reads QueueNotify register to get
notification structure and calculate notification addresses of
each virtqueue.

Co-developed-by: Chao Peng <chao.p.peng@linux.intel.com>
Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
Co-developed-by: Liu Jiang <gerry@linux.alibaba.com>
Signed-off-by: Liu Jiang <gerry@linux.alibaba.com>
Co-developed-by: Zha Bin <zhabin@linux.alibaba.com>
Signed-off-by: Zha Bin <zhabin@linux.alibaba.com>
Signed-off-by: Jing Liu <jing2.liu@linux.intel.com>
---
content.tex | 53 ++++++++++++++++++++++++++++++++++++++++-------------
1 file changed, 40 insertions(+), 13 deletions(-)

diff --git a/content.tex b/content.tex
index 826bc7d..5881253 100644
--- a/content.tex
+++ b/content.tex
@@ -1671,20 +1671,18 @@ \subsection{MMIO Device Register Layout}\label{sec:Virtio Transport Options / Vi
accesses apply to the queue selected by writing to \field{QueueSel}.
}
\hline
- \mmioreg{QueueNotify}{Queue notifier}{0x050}{W}{%
- Writing a value to this register notifies the device that
- there are new buffers to process in a queue.
+ \mmioreg{QueueNotify}{Queue notifier}{0x050}{RW}{%
+ When VIRTIO_F_MMIO_NOTIFICATION has not been negotiated, writing to 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_MMIO_NOTIFICATION has been negotiated, reading this register
+ returns the virtqueue notification structure for calculating notification location.

- When VIRTIO_F_NOTIFICATION_DATA has been negotiated,
- the \field{Notification data} value has the following format:
+ See \ref{sec:Virtio Transport Options / Virtio Over MMIO / MMIO-specific Initialization And Device Operation / Notification Structure Layout}
+ for the notification structure format.

- \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 MMIO / MMIO-specific Initialization And Device Operation / Available Buffer Notifications}
+ for the notification data format.
}
\hline
\mmioreg{InterruptStatus}{Interrupt status}{0x60}{R}{%
@@ -1858,6 +1856,31 @@ \subsubsection{Device Initialization}\label{sec:Virtio Transport Options / Virti
Further initialization MUST follow the procedure described in
\ref{sec:General Initialization And Device Operation / Device Initialization}~\nameref{sec:General Initialization And Device Operation / Device Initialization}.

+\subsubsection{Notification Structure Layout}\label{sec:Virtio Transport Options / Virtio Over MMIO / MMIO-specific Initialization And Device Operation / Notification Structure Layout}
+
+When VIRTIO_F_MMIO_NOTIFICATION has been negotiated, the notification location is calculated
+by notification structure. Driver reads \field{QueueNotify} to get this structure formatted
+as follows.
+
+\begin{lstlisting}
+le32 {
+ notify_base : 16;
+ notify_multiplier : 16;
+};
+\end{lstlisting}
+
+\field{notify_multiplier} is combined with virtqueue index to derive the Queue Notify address
+within a memory mapped control registers for a virtqueue:
+
+\begin{lstlisting}
+ notify_base + queue_index * notify_multiplier
+\end{lstlisting}
+
+\begin{note}
+For example, if notify_multiplier is 0, the device uses the same Queue Notify address for all
+queues.
+\end{note}
+
\subsubsection{Virtqueue Configuration}\label{sec:Virtio Transport Options / Virtio Over MMIO / MMIO-specific Initialization And Device Operation / Virtqueue Configuration}

The driver will typically initialize the virtual queue in the following way:
@@ -1893,16 +1916,20 @@ \subsubsection{Available Buffer Notifications}\label{sec:Virtio Transport Option
When VIRTIO_F_NOTIFICATION_DATA has not been negotiated,
the driver sends an available buffer notification to the device by writing
the 16-bit virtqueue index
-of the queue to be notified to \field{QueueNotify}.
+of the queue to be notified to Queue Notify address.

When VIRTIO_F_NOTIFICATION_DATA has been negotiated,
the driver sends an available buffer notification to the device by writing
-the following 32-bit value to \field{QueueNotify}:
+the following 32-bit value to Queue Notify address:
\lstinputlisting{notifications-le.c}

See \ref{sec:Virtqueues / Driver notifications}~\nameref{sec:Virtqueues / Driver notifications}
for the definition of the components.

+For device not offering VIRTIO_F_MMIO_NOTIFICATION, the Queue Notify address is \field{QueueNotify}.
+For device offering VIRTIO_F_MMIO_NOTIFICATION, see \ref{sec:Virtio Transport Options / Virtio Over MMIO / MMIO-specific Initialization And Device Operation / Notification Structure Layout}
+for how to calculate the Queue Notify address.
+
\subsubsection{Notifications From The Device}\label{sec:Virtio Transport Options / Virtio Over MMIO / MMIO-specific Initialization And Device Operation / Notifications From The Device}

The memory mapped virtio device is using a single, dedicated
--
2.7.4
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