Re: [virtio-comment] [PATCH v3] virtio-rng: add a control queue

[Stefan Hajnoczi <stefanha@redhat.com>]

On Tue, Aug 04, 2020 at 05:41:27PM +0200, Laurent Vivier wrote:

Why can't the driver reset the device so that the buffers are no longer
owned by the device?

> +\subsubsection{Request Virtqueue Flushing}\label{sec:Device Types / Entropy Device / Device Operation / Control Virtqueue / Request Virtqueue Flushing}
> +
> +When the device is not able to provide enough entropy to the driver, the driver may be stuck waiting for the device returning buffers, and cannot be removed to switch to another one.

s/returning/to return/

"cannot be removed to switch to another one"? Is this referring to
hot unplug?

> +The flush command allows the driver to ask the device to release all the buffers sent to the
> +device. This allows the driver to release resources allocated to receive data from the device.
> +
> +\begin{lstlisting}
> +#define VIRTIO_RNG_CMD_FLUSH 0
> +\end{lstlisting}
> +
> +\devicenormative{\paragraph}{Request Virtqueue Flushing}{Device Types / Entropy Device / Device Operation / Control Virtqueue / Request Virtqueue Flushing}
> +
> +When the driver sends a flush request, the device MUST release all outstanding buffers.

"releasing" a buffer is not term defined by the VIRTIO. I guess the full
explanation is:

  When the driver sends a flush request, the device MUST use all
  available requestq buffers and set the used length to 0.

?

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