On Wed, Jan 10, 2018 at 11:47:58AM +0200, Michael S. Tsirkin wrote:
[...]
+\subsection{Supplying Buffers to The Device}\label{sec:Basic Facilities of a
Virtio Device / Packed Virtqueues / Supplying Buffers to The Device}
+
+The driver offers buffers to one of the device's virtqueues as follows:
+
+\begin{enumerate}
+\item The driver places the buffer into free descriptor in the Descriptor Ring.
+
+\item The driver performs a suitable memory barrier to ensure that it updates
+ the descriptor(s) before checking for notification suppression.
+
+\item If notifications are not suppressed, the driver notifies the device
+ of the new available buffers.
+\end{enumerate}
+
+What follows is the requirements of each stage in more detail.
+
+\subsubsection{Placing Available Buffers Into The Descriptor
Ring}\label{sec:Basic Facilities of a Virtio Device / Virtqueues / Supplying
Buffers to The Device / Placing Available Buffers Into The Descriptor Ring}
+
+For each buffer element, b:
+
+\begin{enumerate}
+\item Get the next descriptor table entry, d
+\item Get the next free buffer id value
+\item Set \field{d.addr} to the physical address of the start of b
+\item Set \field{d.len} to the length of b.
+\item Set \field{d.id} to the buffer id
+\item Calculate the flags as follows:
+\begin{enumerate}
+\item If b is device-writable, set the VIRTQ_DESC_F_WRITE bit to 1, otherwise 0
+\item Set VIRTQ_DESC_F_AVAIL bit to the current value of the Available Ring
Wrap Counter
+\item Set VIRTQ_DESC_F_AVAIL bit to inverse value
This should be "Set VIRTQ_DESC_F_USED bit to inverse value, no?
regards,
Jens
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