Re: [virtio-dev] [PATCH v6 4/5] packed virtqueues: more efficient virtqueue layout

[Jens Freimann <jfreimann@redhat.com>]

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