On Tue, Aug 15, 2023 at 03:29:01AM +0800, Zhu Lingshan wrote: > This patch adds new device facility to save and restore virtqueue > state. The virtqueue state is split into two parts: > > - The available state: The state that is used for read the next > available buffer. > - The used state: The state that is used for make buffer used. > > This will simply the transport specific method implemention. E.g two > le16 could be used instead of a single le32). For split virtqueue, we > only need the available state since the used state is implemented in > the virtqueue itself (the used index). For packed virtqueue, we need > both the available state and the used state. > > Those states are required to implement live migration support for > virtio device. > > Signed-off-by: Jason Wang <[email protected]> > Signed-off-by: Zhu Lingshan <[email protected]> > --- > content.tex | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 62 insertions(+) > > diff --git a/content.tex b/content.tex > index 1bb4401..074f43e 100644 > --- a/content.tex > +++ b/content.tex > @@ -516,6 +516,68 @@ \section{Exporting Objects}\label{sec:Basic Facilities > of a Virtio Device / Expo > types. It is RECOMMENDED that devices generate version 4 > UUIDs as specified by \hyperref[intro:rfc4122]{[RFC4122]}. > > +\section{Virtqueue State}\label{sec:Virtqueues / Virtqueue State} > + > +When VIRTIO_F_QUEUE_STATE is negotiated, the driver can set and > +get the device internal virtqueue state through the following > +fields. The implementation of the interfaces is transport specific. > + > +\subsection{\field{Available State} Field} > + > +The available state field is two bytes virtqueue state that is used by
"two bytes of virtqueue state"
> +the device to read the next available buffer.
> +
> +When VIRTIO_RING_F_PACKED is not negotiated, it contains:
> +
> +\begin{lstlisting}
> +le16 last_avail_idx;
> +\end{lstlisting}
> +
> +The \field{last_avail_idx} field is the free-running available ring
> +index where the device will read the next available head of a
> +descriptor chain.
> +
> +See also \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / The
> Virtqueue Available Ring}.
> +
> +When VIRTIO_RING_F_PACKED is negotiated, it contains:
> +
> +\begin{lstlisting}
> +le16 {
> + last_avail_idx : 15;
> + last_avail_wrap_counter : 1;
> +};
> +\end{lstlisting}
> +
> +The \field{last_avail_idx} field is the free-running location
> +where the device read the next descriptor from the virtqueue descriptor ring.
> +
> +The \field{last_avail_wrap_counter} field is the last driver ring wrap
> +counter that was observed by the device.
> +
> +See also \ref{sec:Packed Virtqueues / Driver and Device Ring Wrap Counters}.
> +
> +\subsection{\field{Used State} Field}
> +
> +The used state field is two bytes of virtqueue state that is used by
> +the device when marking a buffer used.
Please specify the non-packed case:
"When VIRTIO_RING_F_PACKED is not negotiated, the 16-bit value is always
0."
> +
> +When VIRTIO_RING_F_PACKED is negotiated, the used state contains:
> +
> +\begin{lstlisting}
> +le16 {
> + used_idx : 15;
> + used_wrap_counter : 1;
> +};
> +\end{lstlisting}
> +
> +The \field{used_idx} field is the free-running location where the device
> write next
"device writes the next"
> +used descriptor to the descriptor ring.
> +
> +The \field{used_wrap_counter} field is the wrap counter that is used
> +by the device.
> +
> +See also \ref{sec:Packed Virtqueues / Driver and Device Ring Wrap Counters}.
> +
> \input{admin.tex}
>
> \chapter{General Initialization And Device Operation}\label{sec:General
> Initialization And Device Operation}
> --
> 2.35.3
>
>
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