On Tue, 11 Apr 2023 22:23:33 +0300
Parav Pandit <
parav@nvidia.com> wrote:
> Currently queue_notify_data register indicates the device
> internal queue notification content. This register is
> meaningful only when feature bit VIRTIO_F_NOTIF_CONFIG_DATA is
> negotiated.
>
> However, above register name often get confusing association with
> very similar feature bit VIRTIO_F_NOTIFICATION_DATA.
>
> When VIRTIO_F_NOTIFICATION_DATA feature bit is negotiated,
> notification really involves sending additional queue progress
> related information (not queue identifier or index).
>
> Hence
> 1. to avoid any misunderstanding and association of
> queue_notify_data with similar name VIRTIO_F_NOTIFICATION_DATA,
>
> and
> 2. to reflect that queue_notify_data is the actual device
> internal virtqueue identifier/index/data/cookie,
>
> a. rename queue_notify_data to queue_notify_config_data.
> queue_notify_config_data.
>
> b. rename ambiguous vqn to a union of vq_index and vq_config_data
>
> c. The driver notification section assumes that queue notification contains
> vq index always. CONFIG_DATA feature bit introduction missed to
> update the driver notification section. Hence, correct it.
>
> Signed-off-by: Parav Pandit <
parav@nvidia.com>
>
> ---
> changelog:
> v12->v13:
> - replace _id with _config_data
> - dropped vq identifier
> - dropped the idea of union as description is for config data feature
> v11->v12:
> - new patch
> ---
> content.tex | 11 ++++++++---
> notifications-be.c | 2 +-
> notifications-le.c | 2 +-
> transport-pci.tex | 26 ++++++++++++++++----------
> 4 files changed, 26 insertions(+), 15 deletions(-)
>
> diff --git a/content.tex b/content.tex
> index e79d722..601c069 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -404,8 +404,12 @@ \section{Driver Notifications} \label{sec:Basic Facilities of a Virtio Device /
> notification to the device.
>
> When VIRTIO_F_NOTIFICATION_DATA has not been negotiated,
> -this notification involves sending the
> -virtqueue index to the device (method depending on the transport).
> +this notification contains either virtqueue
> +index if VIRTIO_F_NOTIF_CONFIG_DATA is not negotiated or device
> +supplied virtqueue notification data if
> +VIRTIO_F_NOTIF_CONFIG_DATA is negotiated.
> +
> +A method to supply such virtqueue notification data is transport specific.
>
> However, some devices benefit from the ability to find out the
> amount of available data in the queue without accessing the virtqueue in memory:
> @@ -416,7 +420,8 @@ \section{Driver Notifications} \label{sec:Basic Facilities of a Virtio Device /
> the following information:
>
> \begin{description}
> -\item [vqn] VQ number to be notified.
> +\item [vq_index_config_data] either virtqueue index or device supplied
> + queue notification config data corresponding to a virtqueue.
> \item [next_off] Offset
> within the ring where the next available ring entry
> will be written.
> diff --git a/notifications-be.c b/notifications-be.c
> index 5be947e..02f0624 100644
> --- a/notifications-be.c
> +++ b/notifications-be.c
> @@ -1,5 +1,5 @@
> be32 {
> - vqn : 16;
> + vq_config_data: 16; /* previously known as vqn */
> next_off : 15;
> next_wrap : 1;
> };
> diff --git a/notifications-le.c b/notifications-le.c
> index fe51267..f73c6a5 100644
> --- a/notifications-le.c
> +++ b/notifications-le.c
> @@ -1,5 +1,5 @@
> le32 {
> - vqn : 16;
> + vq_config_data: 16; /* previously known as vqn */
Is this where the union was supposed to go? I.e.
something like:
union {
le16 vq_config_data;
le16 vq_index;
} vq_index_config_data;
(You said in the v12 disussion in MID
<
PH0PR12MB54812C754ED9063E34E06E1BDC9A9@PH0PR12MB5481.namprd12.prod.outlook.com>
that you are going to change vqn to the union of vq_config_data and
vq_index, although vq_notif_config_data might be preferable).
Or did you mean to do
+ vq_index_config_data: 16; /* previously known as vqn */
Of course, this has an impact on the rest of the text...
> next_off : 15;
> next_wrap : 1;
> };
> diff --git a/transport-pci.tex b/transport-pci.tex
> index 5d98467..53c8ee6 100644
> --- a/transport-pci.tex
> +++ b/transport-pci.tex
> @@ -319,7 +319,7 @@ \subsubsection{Common configuration structure layout}\label{sec:Virtio Transport
> le64 queue_desc; /* read-write */
> le64 queue_driver; /* read-write */
> le64 queue_device; /* read-write */
> - le16 queue_notify_data; /* read-only for driver */
> + le16 queue_notify_config_data; /* read-only for driver */
> le16 queue_reset; /* read-write */
> };
> \end{lstlisting}
> @@ -388,17 +388,21 @@ \subsubsection{Common configuration structure layout}\label{sec:Virtio Transport
> \item[\field{queue_device}]
> The driver writes the physical address of Device Area here. See section \ref{sec:Basic Facilities of a Virtio Device / Virtqueues}.
>
> -\item[\field{queue_notify_data}]
> +\item[\field{queue_notify_config_data}]
> This field exists only if VIRTIO_F_NOTIF_CONFIG_DATA has been negotiated.
> - The driver will use this value to put it in the 'virtqueue number' field
> - in the available buffer notification structure.
> + The driver will use this value when driver sends available buffer
> + notification to the device.
> See section \ref{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Available Buffer Notifications}.
> \begin{note}
> This field provides the device with flexibility to determine how virtqueues
> will be referred to in available buffer notifications.
> - In a trivial case the device can set \field{queue_notify_data}=vqn. Some devices
> - may benefit from providing another value, for example an internal virtqueue
> - identifier, or an internal offset related to the virtqueue number.
> + In a trivial case the device can set \field{queue_notify_config_data} to
> + virtqueue index. Some devices may benefit from providing another value,
> + for example an internal virtqueue identifier, or an internal offset
> + related to the virtqueue index.
> + \end{note}
> + \begin{note}
> + This field is previously known as queue_notify_data.
> \end{note}
>
> \item[\field{queue_reset}]
> @@ -468,7 +472,9 @@ \subsubsection{Common configuration structure layout}\label{sec:Virtio Transport
>
> \drivernormative{\paragraph}{Common configuration structure layout}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Common configuration structure layout}
>
> -The driver MUST NOT write to \field{device_feature}, \field{num_queues}, \field{config_generation}, \field{queue_notify_off} or \field{queue_notify_data}.
> +The driver MUST NOT write to \field{device_feature}, \field{num_queues},
> +\field{config_generation}, \field{queue_notify_off} or
> +\field{queue_notify_config_data}.
>
> If VIRTIO_F_RING_PACKED has been negotiated,
> the driver MUST NOT write the value 0 to \field{queue_size}.
> @@ -1053,9 +1059,9 @@ \subsubsection{Available Buffer Notifications}\label{sec:Virtio Transport Option
> If VIRTIO_F_NOTIF_CONFIG_DATA has been negotiated:
> \begin{itemize}
> \item If VIRTIO_F_NOTIFICATION_DATA has not been negotiated, the driver MUST use the
> -\field{queue_notify_data} value instead of the virtqueue index.
> +\field{queue_notify_id} value instead of the virtqueue index.
> \item If VIRTIO_F_NOTIFICATION_DATA has been negotiated, the driver MUST set the
> -\field{vqn} field to the \field{queue_notify_data} value.
> +\field{vq_notify_id} field to the \field{queue_notify_id} value.
Seems you did not catch these with the s/_id/_config_data/. By doing the
replace one would get queue_notify_config_data, vq_notify_config_data
and queue_notify_config_data respectively.
But that still does not seem right, and the right answer depends on
to what do we rename \field{vqn}.
Regards,
Halil
> \end{itemize}
>
> \subsubsection{Used Buffer Notifications}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Used Buffer Notifications}