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Subject: [PATCH v14 03/11] content: Rename confusing queue_notify_data and vqn names
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_notif_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. Fixes: https://github.com/oasis-tcs/virtio-spec/issues/163 Signed-off-by: Parav Pandit <parav@nvidia.com> --- changelog: v13->v14: - added pci transport specific union structure - added normative lines for case when VIRTIO_F_NOTIF_CONFIG_DATA is not negotiated. - added normataive lines for clarify bit-width for driver notification - replace left over _id with _config_data - use _notif_config_data name to align to feature name 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 +- notifications-pci-le.c | 8 +++++ transport-pci.tex | 72 +++++++++++++++++++++++++++++++----------- 5 files changed, 71 insertions(+), 24 deletions(-) create mode 100644 notifications-pci-le.c diff --git a/content.tex b/content.tex index e79d722..e1345ea 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 config data if +VIRTIO_F_NOTIF_CONFIG_DATA is negotiated. + +A notification method and suppling such virtqueue notification config 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..bf6d1cd 100644 --- a/notifications-be.c +++ b/notifications-be.c @@ -1,5 +1,5 @@ be32 { - vqn : 16; + vq_index: 16; /* previously known as vqn */ next_off : 15; next_wrap : 1; }; diff --git a/notifications-le.c b/notifications-le.c index fe51267..8a19389 100644 --- a/notifications-le.c +++ b/notifications-le.c @@ -1,5 +1,5 @@ le32 { - vqn : 16; + vq_index: 16; /* previously known as vqn */ next_off : 15; next_wrap : 1; }; diff --git a/notifications-pci-le.c b/notifications-pci-le.c new file mode 100644 index 0000000..ef60d15 --- /dev/null +++ b/notifications-pci-le.c @@ -0,0 +1,8 @@ +le32 { + union { + vq_index: 16; /* Used if VIRTIO_F_NOTIF_CONFIG_DATA not negotiated */ + vq_notif_config_data: 16; /* Used if VIRTIO_F_NOTIF_CONFIG_DATA negotiated */ + }; + next_off : 15; + next_wrap : 1; +}; diff --git a/transport-pci.tex b/transport-pci.tex index 5d98467..04a9a80 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_notif_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_notif_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_notif_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_notif_config_data}. If VIRTIO_F_RING_PACKED has been negotiated, the driver MUST NOT write the value 0 to \field{queue_size}. @@ -1035,13 +1041,22 @@ \subsubsection{Available Buffer Notifications}\label{sec:Virtio Transport Option When VIRTIO_F_NOTIFICATION_DATA has not been negotiated, the driver sends an available buffer notification to the device by writing -the 16-bit virtqueue index -of this virtqueue to the Queue Notify address. +only the 16-bit notification value to the Queue Notify address of the +virtqueue. A notification value depends on the negotiation of +VIRTIO_F_NOTIF_CONFIG_DATA. -When VIRTIO_F_NOTIFICATION_DATA has been negotiated, -the driver sends an available buffer notification to the device by writing -the following 32-bit value to the Queue Notify address: -\lstinputlisting{notifications-le.c} +\item If VIRTIO_F_NOTIFICATION_DATA has been negotiated, the driver sends an +available buffer notification to the device by writing the following 32-bit +value to the Queue Notify address: +\lstinputlisting{notifications-pci-le.c} + +\begin{itemize} +\item When VIRTIO_F_NOTIF_CONFIG_DATA is not negotiated \field{vq_index} is set +to the virtqueue index. + +\item When VIRTIO_F_NOTIFICATION_DATA is negotiated, +\field{vq_notif_config_data} is set to \field{queue_notif_config_data}. +\end{itemize} See \ref{sec:Basic Facilities of a Virtio Device / Driver notifications}~\nameref{sec:Basic Facilities of a Virtio Device / Driver notifications} for the definition of the components. @@ -1050,12 +1065,31 @@ \subsubsection{Available Buffer Notifications}\label{sec:Virtio Transport Option for how to calculate the Queue Notify address. \drivernormative{\paragraph}{Available Buffer Notifications}{Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Available Buffer Notifications} -If VIRTIO_F_NOTIF_CONFIG_DATA has been negotiated: + +If VIRTIO_F_NOTIFICATION_DATA is not negotiated, the driver notification +MUST be a 16-bit notification. + +If VIRTIO_F_NOTIFICATION_DATA is negotiated, the driver notification +MUST be a 32-bit notification. + +If VIRTIO_F_NOTIF_CONFIG_DATA is not negotiated: +\begin{itemize} +\item If VIRTIO_F_NOTIFICATION_DATA is not negotiated, the driver MUST set the +notification value to virtqueue index. + +\item If VIRTIO_F_NOTIFICATION_DATA is negotiated, the driver MUST set the +\field{vq_index} to the virtqueue index. + +\end{itemize} + +If VIRTIO_F_NOTIF_CONFIG_DATA is 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. -\item If VIRTIO_F_NOTIFICATION_DATA has been negotiated, the driver MUST set the -\field{vqn} field to the \field{queue_notify_data} value. +\item If VIRTIO_F_NOTIFICATION_DATA is not negotiated, the driver MUST set +the notification value to \field{queue_notif_config_data}. + +\item If VIRTIO_F_NOTIFICATION_DATA is not negotiated, the driver MUST set the +\field{vq_notify_config_data} to the \field{queue_notif_config_data} +value. \end{itemize} \subsubsection{Used Buffer Notifications}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Used Buffer Notifications} -- 2.26.2
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