Re: [PATCH v3 1/2] virtio: introduce virtqueue reset as basic facility

[Jason Wang <jasowang@redhat.com>]

On Mon, Sep 27, 2021 at 8:32 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
>
> This patch allows the driver to reset a queue individually.
>
> This is very common on general network equipment. By disabling a queue,
> you can quickly reclaim the buffer currently on the queue. If necessary,
> we can reinitialize the queue separately.
>
> For example, when virtio-net implements support for AF_XDP, we need to
> disable a queue to release all the original buffers when AF_XDP setup.
> And quickly release all the AF_XDP buffers that have been placed in the
> queue when AF_XDP exits.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> ---
>  content.tex | 41 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
>
> diff --git a/content.tex b/content.tex
> index 37c45d3..603b1f1 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -407,6 +407,43 @@ \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 Reset}\label{sec:Virtqueues / Virtqueue Reset}
> +
> +When VIRTIO_F_RING_RESET is negotiated, the driver can reset a virtqueue
> +individually. The way to reset the virtqueue is transport specific.
> +
> +Virtqueue reset is divided into two parts. The driver MUST reset stop a queue
> +first, and then re-enable the queue. The re-enable part is optional.
> +
> +\devicenormative{\subsection}{Virtqueue Reset Stop}{Virtqueues / Virtqueue Reset}
> +The device MUST not executes the requests from this virtqueue, and notify the
> +driver.
> +
> +And the device MUST initialize all states of this virtqueue, including the
> +available state and the used state.
> +
> +\drivernormative{\subsection}{Virtqueue Reset Stop}{Virtqueues / Virtqueue Reset}
> +
> +The driver MUST first notify

What did "notify" mean here? I guess it means the transport specific
way to stop a virtqueue?

Thanks

> the device and confirm that we have successfully
> +stopped a queue.
> +
> +Then the driver can release all the resources occupied by this virtqueue.
> +And reinitialize the state of this queue.
> +
> +\devicenormative{\subsection}{Virtqueue Reset Re-enable}{Virtqueues / Virtqueue Reset}
> +
> +This process is the same as the initialization process of a single queue during
> +the initialization of the entire device. After the device has accepted all the
> +configuration from the driver, it will start working under the notification of the
> +driver.
> +
> +\drivernormative{\subsection}{Virtqueue Reset Re-enable}{Virtqueues / Virtqueue Reset}
> +
> +This process is the same as the initialization process of a single queue during
> +the entire device initialization process. After the driver allocates resources
> +and completes the configuration of the queue status, it notifies the device to
> +start working.
> +
>  \chapter{General Initialization And Device Operation}\label{sec:General Initialization And Device Operation}
>
>  We start with an overview of device initialization, then expand on the
> @@ -6673,6 +6710,10 @@ \chapter{Reserved Feature Bits}\label{sec:Reserved Feature Bits}
>    transport specific.
>    For more details about driver notifications over PCI see \ref{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Available Buffer Notifications}.
>
> +  \item[VIRTIO_F_RING_RESET(40)] This feature indicates
> +  that the driver can reset a queue individually.
> +  See \ref{sec:Virtqueues / Virtqueue Reset}.
> +
>  \end{description}
>
>  \drivernormative{\section}{Reserved Feature Bits}{Reserved Feature Bits}
> --
> 2.31.0
>