Re: [virtio-comment] [RFC PATCH 3/5] virtio: The actions by the device upon SUSPEND

[Stefan Hajnoczi <stefanha@redhat.com>]

On Tue, Aug 15, 2023 at 03:29:02AM +0800, Zhu Lingshan wrote:
> This commit specifies the actions to be taken by the device upon
> SUSPEND.
> 
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> Signed-off-by: Eugenio PÃrez <eperezma@redhat.com>
> Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
> ---
>  content.tex | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/content.tex b/content.tex
> index 074f43e..43bd5de 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -96,6 +96,15 @@ \section{\field{Device Status} Field}\label{sec:Basic Facilities of a Virtio Dev
>  If VIRTIO_F_SUSPEND is negotiated and SUSPEND is set, the device MUST clear SUSPEND
>  and resumes operation upon DRIVER_OK.
>  
> +If VIRTIO_F_SUSPEND is negotiated, when SUSPEND is set, the device MUST perform the following operations:

"when SUSPEND is set" is ambigious. It could mean when the driver writes
the Device Status Field, when the device transitions to SUSPEND, or
something else. Maybe "before the device reports the SUSPEND bit set in
the Device Status Field"?

> +\begin{itemize}
> +\item Stop comsuming any descriptors

"consuming"

It may be more consistent to talk about virtqueue buffers (i.e.
requests) rather than descriptors here.

> +\item Mark all finished descriptors as used and send used buffer notification to the driver

The device has to complete everything that is in flight, just completing
"finished" stuff is not enough. Does "finished descriptors" really mean
"in-flight virtqueue buffers"?

"send a used buffer notification" or "send used buffer notifications"

> +\item Record Virtqueue State of each enabled virtqueue, see section \ref{sec:Virtqueues / Virtqueue State}

Does "Record" mean that Virtqueue State fields can only be accessed by
the driver while device is paused (they may be outdated or invalid while
the device is unpaused)?

> +\item Pause its operation and preserve all configurations in its Device Configuration Space, see \ref{sec:Basic Facilities of a Virtio Device / Device Configuration Space}

What does "preserve" mean? Does it mean the Device Configuration Space
is not allowed to change during SUSPEND?

> +\item Present SUSPEND in \field{device status}
> +\end{itemize}
> +
>  \section{Feature Bits}\label{sec:Basic Facilities of a Virtio Device / Feature Bits}
>  
>  Each virtio device offers all the features it understands.  During
> -- 
> 2.35.3
> 
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