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Subject: Re: [virtio-comment] [PATCH v4 4/7] transport-fabrics: introduce command set
As noted in my high level feedback I think the protocol should have redirection semantics.
> On Jun 26, 2023, at 3:25 AM, zhenwei pi <pizhenwei@bytedance.com> wrote:
>
> Introduce command set for Virtio-oF which includes:
> - command id: a tag to distinguish in-flight commands
> - status: indicate the result of a Virtio-oF command
> - opcodes: the Virtio-oF transport layer commands use 0x0000-0x0fff,
> and the device layer commands use 0x1000-0xffff.
> get/set status/feature/ config use consecutive number.
>
> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
> ---
> transport-fabrics.tex | 616 ++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 616 insertions(+)
>
> diff --git a/transport-fabrics.tex b/transport-fabrics.tex
> index d562b2c..3fd9e8e 100644
> --- a/transport-fabrics.tex
> +++ b/transport-fabrics.tex
> @@ -113,3 +113,619 @@ \subsubsection{Keyed Data Transfers}\label{sec:Virtio Transport Options / Virtio
> |COMP| |COMP| |COMP|
> +----+ +----+ +----+
> \end{lstlisting}
> +
> +
> +\subsection{Commands Definition}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition}
> +This section defines data structures, opcodes, and status for Virtio-oF.
> +A Virtio-oF command is fixed to 16 bytes, and a Virtio-oF completion is fixed to 16 bytes.
> +Note that the reserved fields of Virtio-oF commands and completions are filled with zero.
> +
> +\subsubsection{Command ID}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Command ID}
> +The Command ID (le16 type) is used to uniquely describe a Virtio-oF PDU for identification.
> +Generally, the Virtio-oF initiator allocates a Command ID that is unique for all in-flight commands,
> +and the Virtio-oF target specifies the same Command ID for completion.
> +
> +Command IDs 0xff00 - 0xffff are reserved for the Virtio-oF control queue asynchronous events.
> +The reserved Command IDs for the Virtio-oF control queue are as follows:
> +
> +\begin{tabular}{ |l|l| }
> +\hline
> +Command ID & Description \\
> +\hline \hline
> +0xfffe & Config change. Causes the initiator to generate a configuration change notification \\
> +\hline
> +0xffff & Keepalive. The initiator ignores this event \\
> +\hline
> +0xff00 - 0xfffd & Reserved \\
> +\hline
> +\end{tabular}
> +
> +\subsubsection{Status}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Status}
> +The Status (le16 type) of a Virtio-oF completion is used to indicate the result of a Virtio-oF command in detail.
> +The status values are defined as follows:
> +
> +\begin{lstlisting}
> +/* command executed successfully */
> +#define VIRTIO_OF_STATUS_SUCCESS 0x0000
> +
> +/* unrecognized command, or disabled command due to unsupported feature */
> +#define VIRTIO_OF_STATUS_ENOCMD 0x0001
> +/* in-flight commands exceeded queue size */
> +#define VIRTIO_OF_STATUS_ECMDQUOT 0x0002
> +
> +/* no such target specified by TVQN */
> +#define VIRTIO_OF_STATUS_ENOTGT 0x1001
> +/* failed to create Virtio-oF device instance */
> +#define VIRTIO_OF_STATUS_ENODEV 0x1002
> +/* rejected due to access control */
> +#define VIRTIO_OF_STATUS_EACLREJECTED 0x1003
> +/* bad Virtio-oF device instance ID */
> +#define VIRTIO_OF_STATUS_EBADDEV 0x1010
> +/* mismatched TVQN or IVQN from Virtio-oF device instance */
> +#define VIRTIO_OF_STATUS_EBADVQN 0x1011
> +/* Virtio-oF virtqueue index exceeded */
> +#define VIRTIO_OF_STATUS_EQUEUEQUOT 0x1020
> +/* Virtio-oF virtqueue size exceeded */
> +#define VIRTIO_OF_STATUS_EQSIZEQUOT 0x1021
> +
> +/* unsupported Virtio-oF feature */
> +#define VIRTIO_OF_STATUS_EFEATURE 0x2000
> +/* unsupported Virtio-oF device instance status */
> +#define VIRTIO_OF_STATUS_ESTATUS 0x2010
> +/* unsupported Virtio-oF device instance feature */
> +#define VIRTIO_OF_STATUS_EDEVFEATURE 0x2020
> +/* unsupported offset of device configuration space */
> +#define VIRTIO_OF_STATUS_ECONFOFF 0x2030
> +/* unsupported bytes of device configuration space */
> +#define VIRTIO_OF_STATUS_ECONFBYTES 0x2031
> +/* failed to read device-readable virtqueue buffers */
> +#define VIRTIO_OF_STATUS_EOUTVQBUF 0x20f0
> +/* failed to write device-writable virtqueue buffers */
> +#define VIRTIO_OF_STATUS_EINVQBUF 0x20f1
> +\end{lstlisting}
> +
> +\subsubsection{Opcodes}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes}
> +Opcodes (u16 type) of Virtio-oF Commands are as follows:
> +
> +\begin{lstlisting}
> +#define virtio_of_op_connect 0x0000
> +#define virtio_of_op_disconnect 0x0001
> +#define virtio_of_op_keepalive 0x0002
> +#define virtio_of_op_get_feature 0x0004
> +#define virtio_of_op_set_feature 0x0005
> +#define virtio_of_op_get_keyed_num_descs 0x0100
> +#define virtio_of_op_vq 0x0fff
> +#define virtio_of_op_get_vendor_id 0x1000
> +#define virtio_of_op_get_device_id 0x1001
> +#define virtio_of_op_reset_device 0x1003
> +#define virtio_of_op_get_status 0x1004
> +#define virtio_of_op_set_status 0x1005
> +#define virtio_of_op_get_device_feature 0x1006
> +#define virtio_of_op_set_driver_feature 0x1009
> +#define virtio_of_op_get_vq_size 0x100a
> +#define virtio_of_op_get_config 0x100c
> +#define virtio_of_op_set_config 0x100d
> +\end{lstlisting}
> +
> +\paragraph{Connect Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Connect Command}
> +
This would be a good place to introduce some kind of target-side redirect mechanism to support redirecting to another IP.
Probably just another op/status code and message from the target for redirection?
> +The Connect Command is used to establish a Virtio-oF queue for both the Virtio-oF control queue and Virtio-oF virtqueue, it is always the first command to execute on a Virtio-oF queue.
> +
> +The structure of the Connect Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_connect {
> + /* opcode is virtio_of_op_connect */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + /* Virtio-oF device instance ID. 0xffff is reserved for the Virtio-oF control queue */
> + le16 device_instance_id;
> + /* used by Virtio-oF virtqueue only, equal to virtqueue index */
> + le16 vq_index;
> + /* the length of the Connect Body */
> + le32 length;
> +#define VIRTIO_OF_CONTROL_QUEUE_SIZE 32
> + /* the size of a Virtio-oF queue, 0 means the maximum queue size supported */
> + le16 queue_size;
> + u8 reserved[2];
> +};
> +\end{lstlisting}
> +
> +The structure of the Connect Body is as follows:
> +\begin{lstlisting}
> +struct virtio_of_connect {
> + /* Virtio-oF initiator VQN */
> + u8 ivqn[256];
> + /* Virtio-oF target VQN */
> + u8 tvqn[256];
> + u8 reserved[512];
> +};
> +\end{lstlisting}
> +
> +The structure of the Connect Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_connect {
> + le16 status;
> + le16 command_id;
> + /* Virtio-oF device instance ID */
> + le16 device_instance_id;
> + u8 reserved[10];
> +};
> +\end{lstlisting}
> +
> +The Connect Command, Body, and Completion have the following usages:
> +\begin{itemize}
> +\item The Virtio-oF initiator specifies \texttt{device_instance_id} of 0xffff in the Connect command
> +and Virtio-oF initiator/target VQN in the Connect Body to establish the Virtio-oF control queue first.
> +\item The Virtio-oF target allocates any available ID for a newly created Virtio-oF device instance,
> +and specifies the \texttt{device_instance_id} of the new Virtio-oF device instance ID in the Connect Completion.
> +\item The Virtio-oF initiator specifies the Virtio-oF device instance ID and \texttt{vq_index} to establish Virtio-oF virtqueues one by one.
> +The Connect Body is optional for the Virtio-oF virtqueues, once a Virtio-oF virtqueue issues a Connect Command without Connect Body, the Virtio-oF virtqueue uses the same Connect Body as the Virtio-oF control queue.
> +\end{itemize}
> +
> +\paragraph{Disconnect Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Disconnect Command}
> +
> +The Disconnect Command is used to gracefully disconnect both the Virtio-oF control queue and Virtio-oF virtqueue. All in-flight commands are completed upon receipt of the Disconnect Completion.
> +
> +The structure of the Disconnect Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_disconnect {
> + /* opcode is virtio_of_op_disconnect */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + u8 reserved[12];
> +};
> +\end{lstlisting}
> +
> +The structure of the Disconnect Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_disconnect {
> + le16 status;
> + le16 command_id;
> + u8 reserved[12];
> +};
> +\end{lstlisting}
> +
> +The Disconnect Command and Completion have the following usages:
> +\begin{itemize}
> +\item The Virtio-oF initiator should disconnect the Virtio-oF virtqueues before the Virtio-oF control queue.
> +\item Once the Virtio-oF control queue is disconnected, the Virtio-oF device instance and associated resources should be destroyed.
> +\item If the underlying transport connection of a Virtio-oF queue is disconnected without issuing the Disconnect Command, the in-flight commands are not guaranteed to execute successfully.
> +\end{itemize}
> +
> +\paragraph{Keepalive Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Keepalive Command}
> +The Keepalive Command is used as a health check mechanism to detect when a Virtio-oF device instance becomes unavailable, it is used for the Virtio-oF control queue only.
> +Once the Virtio-oF device instance becomes unavailable, the initiator should disconnect all the Virtio-oF queues and release associated resources.
> +
> +The structure of the Keepalive Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_keepalive {
> + /* opcode is virtio_of_op_keepalive */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + u8 reserved[12];
> +};
> +\end{lstlisting}
> +
> +The structure of the Keepalive Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_keepalive {
> + le16 status;
> + le16 command_id;
> + u8 reserved[12];
> +};
> +\end{lstlisting}
> +
> +\paragraph{Get Feature Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Get Feature Command}
> +The Get Feature Command is used to get feature bits of a Virtio-oF device instance for the Virtio-oF control queue only.
> +
> +The structure of the Get Feature Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_get_feature {
> + /* opcode is virtio_of_op_get_feature */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + /* value 0x0 selects feature bits 0 to 63, 0x1 selects feature bits 64 to 127, etc */
> + le32 feature_select;
> + u8 reserved[8];
> +};
> +\end{lstlisting}
> +
> +The structure of the Get Feature Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_get_feature {
> + le16 status;
> + le16 command_id;
> + u8 reserved[4];
> + /* feature bits */
> + le64 feature;
> +};
> +\end{lstlisting}
> +
> +The feature bits of a Virtio-oF device instance are as follows:
> +\begin{lstlisting}
> +/* support virtio_of_op_get_keyed_num_descs to get the maximum number of keyed descriptors */
> +#define VIRTIO_OF_F_KEYED_NUM_DESCS 0
> +\end{lstlisting}
> +
> +\paragraph{Set Feature Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Set Feature Command}
> +The Set Feature Command is used to set the feature bits of a Virtio-oF device instance for the Virtio-oF control queue only.
> +
> +The structure of the Set Feature Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_set_feature {
> + /* opcode is virtio_of_op_set_feature */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + /* value 0x0 selects feature bits 0 to 63, 0x1 selects feature bits 64 to 127, etc */
> + le32 feature_select;
> + /* feature bits */
> + le64 feature;
> +};
> +\end{lstlisting}
> +
> +The structure of the Set Feature Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_set_feature {
> + le16 status;
> + le16 command_id;
> + u8 reserved[12];
> +};
> +\end{lstlisting}
> +
> +Note: it is recommended that the
> +\nameref{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Get Feature Command}
> +and Set Feature Command should be executed upon the establishment of the Virtio-oF control queue for feature negotiation.
> +However, they are allowed to be executed during the Virtio-oF control queue lifecycle.
> +
> +\paragraph{Get Keyed Number Descriptors Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Get Keyed Number Descriptors Command}
> +The Get Keyed Number Descriptors Command is used to get the maximum number of keyed descriptors of Virtio-oF virtqueues, it is executed on the Virtio-oF control queue.
> +
> +The structure of the Get Keyed Number Descriptors Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_get_keyed_num_descs {
> + /* opcode is virtio_of_op_get_keyed_num_descs */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + u8 reserved[12];
> +};
> +\end{lstlisting}
> +
> +The structure of the Get Keyed Number Descriptors Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_get_keyed_num_descs {
> + le16 status;
> + le16 command_id;
> + /* the maximum number of keyed descriptors */
> + u8 descs;
> + u8 reserved[11];
> +};
> +\end{lstlisting}
> +
> +\paragraph{VQ Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / VQ Command}
> +The VQ Command is used to transmit virtqueue buffers for Virtio-oF virtqueue only.
> +
> +The structure of the VQ Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_vq {
> + /* opcode is virtio_of_op_vq */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + u8 reserved[4];
> + /* the length of device-readable virtqueue buffers */
> + le32 out_length;
> + /* the length of device-writable virtqueue buffers */
> + le32 in_length;
> +};
> +\end{lstlisting}
> +
> +The structure of the VQ Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_vq {
> + le16 status;
> + le16 command_id;
> + /* the length of virtqueue buffers from Virtio-oF target */
> + le32 length;
> + u8 reserved[8];
> +};
> +\end{lstlisting}
> +
> +For \nameref{sec:Virtio Transport Options / Virtio Over Fabrics / Protocol Data Unit/ Stream Data Transfers},
> +\texttt{out_length} of virtio_of_command_vq describes the following bytes in a request Virtio-oF PDU,
> +and \texttt{length} of virtio_of_completion_vq describes the following bytes in a response Virtio-oF PDU.
> +
> +For \nameref{sec:Virtio Transport Options / Virtio Over Fabrics / Protocol Data Unit/ Keyed Data Transfers},
> +there are 1 or more keyed descriptors (virtio_of_keyed_desc type) in a request Virtio-oF PDU to describe the virtqueue buffers of \texttt{out_length + in_length} bytes,
> +and \texttt{length} of virtio_of_completion_vq describes the number of bytes written into the device writable portion of the buffer described by the keyed descriptors.
> +
> +\paragraph{Get Vendor ID Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Get Vendor ID Command}
> +The Get Vendor ID Command is used to get the Virtio Vendor ID of a Virtio-oF device instance for the Virtio-oF control queue only.
> +
> +The structure of the Get Vendor ID Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_get_vendor_id {
> + /* opcode is virtio_of_op_get_vendor_id */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + u8 reserved[12];
> +};
> +\end{lstlisting}
> +
> +The structure of the Get Vendor ID Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_get_vendor_id {
> + le16 status;
> + le16 command_id;
> + /* Virtio Vendor ID */
> + le32 vendor_id;
> + u8 reserved[8];
> +};
> +\end{lstlisting}
> +
> +\paragraph{Get Device ID Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Get Device ID Command}
> +The Get Device ID Command is used to get the Virtio Device ID of a Virtio-oF device instance for the Virtio-oF control queue only.
> +
> +The structure of the Get Device ID Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_get_device_id {
> + /* opcode is virtio_of_op_get_device_id */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + u8 reserved[12];
> +};
> +\end{lstlisting}
> +
> +The structure of the Get Device ID Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_get_device_id {
> + le16 status;
> + le16 command_id;
> + /* Virtio Device ID */
> + le32 device_id;
> + u8 reserved[8];
> +};
> +\end{lstlisting}
> +
> +\paragraph{Reset Device Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Reset Device Command}
> +The Reset Device Command is used to reset a Virtio-oF device instance for the Virtio-oF control queue only.
> +
> +The structure of the Reset Device Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_reset_device {
> + /* opcode is virtio_of_op_get_device_id */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + u8 reserved[12];
> +};
> +\end{lstlisting}
> +
> +The structure of the Reset Device Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_reset_device {
> + le16 status;
> + le16 command_id;
> + u8 reserved[12];
> +};
> +\end{lstlisting}
> +
> +\paragraph{Get Status Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Get Status Command}
> +The Get Status Command is used to get the status of a Virtio-oF device instance for the Virtio-oF control queue only.
> +
> +The structure of the Get Status Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_get_status {
> + /* opcode is virtio_of_op_get_status */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + u8 reserved[12];
> +};
> +\end{lstlisting}
> +
> +The structure of the Get Status Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_get_status {
> + le16 status;
> + le16 command_id;
> + /* status of the Virtio-oF device instance */
> + le32 dev_status;
> + u8 reserved[8];
> +};
> +\end{lstlisting}
> +
> +\paragraph{Set Status Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Set Status Command}
> +The Set Status Command is used to set the status of a Virtio-oF device instance for the Virtio-oF control queue only.
> +
> +The structure of the Set Status Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_set_status {
> + /* opcode is virtio_of_op_set_status */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + /* status of the Virtio-oF device instance */
> + le32 status;
> + u8 reserved[8];
> +};
> +\end{lstlisting}
> +
> +The structure of the Set Status Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_set_status {
> + le16 status;
> + le16 command_id;
> + u8 reserved[12];
> +};
> +\end{lstlisting}
> +
> +\paragraph{Get Device Feature Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Get Device Feature Command}
> +The Get Device Feature Command is used to get virtio device feature bits of a Virtio-oF device instance for the Virtio-oF control queue only.
> +
> +The structure of the Get Device Feature Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_get_device_feature {
> + /* opcode is virtio_of_op_get_device_feature */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + /* value 0x0 selects feature bits 0 to 63, 0x1 selects feature bits 64 to 127, etc */
> + le32 feature_select;
> + u8 reserved[8];
> +};
> +\end{lstlisting}
> +
> +The structure of the Get Device Feature Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_get_device_feature {
> + le16 status;
> + le16 command_id;
> + u8 reserved[4];
> + /* feature bits */
> + le64 feature;
> +};
> +\end{lstlisting}
> +
> +\paragraph{Set Driver Feature Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Set Driver Feature Command}
> +The Set Driver Feature Command is used to set virtio driver feature bits of a Virtio-oF device instance for the Virtio-oF control queue only.
> +
> +The structure of the Set Driver Feature Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_set_driver_feature {
> + /* opcode is virtio_of_op_set_driver_feature */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + /* value 0x0 selects feature bits 0 to 63, 0x1 selects feature bits 64 to 127, etc */
> + le32 feature_select;
> + /* feature bits */
> + le64 feature;
> +};
> +\end{lstlisting}
> +
> +The structure of the Set Driver Feature Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_set_driver_feature {
> + le16 status;
> + le16 command_id;
> + u8 reserved[12];
> +};
> +\end{lstlisting}
> +
> +\paragraph{Get VQ Size Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Get VQ Size Command}
> +The Get VQ Size Command is used to get the maximum queue size of a Virtio-oF virtqueue for the Virtio-oF control queue only.
> +
> +The structure of the Get VQ Size Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_get_vq_size {
> + /* opcode is virtio_of_op_get_vq_size */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + /* the Virtio-oF virtqueue index */
> + le16 vq_index;
> + u8 reserved[10];
> +};
> +\end{lstlisting}
> +
> +The structure of the Get VQ Size Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_get_vq_size {
> + le16 status;
> + le16 command_id;
> + /* size of Virtio-oF virtqueues */
> + le16 size;
> + u8 reserved[10];
> +};
> +\end{lstlisting}
> +
> +Note: the Virtio-oF control queue has a fixed queue size, the Virtio-oF initiator can specify a smaller Virtio-oF virtqueue size by
> +\nameref{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Connect Command}.
> +
> +\paragraph{Get Config Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Get Config Command}
> +The Get Config Command is used to get the device configuration space of a Virtio-oF device instance for the Virtio-oF control queue only.
> +
> +The structure of the Get Config Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_get_config {
> + /* opcode is virtio_of_op_get_config */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + /* offset of device configuration space */
> + le16 offset;
> + /* bytes to get, available values: 1, 2, 4, 8 */
> + u8 bytes;
> + u8 reserved[9];
> +};
> +\end{lstlisting}
> +
> +The structure of the Get Config Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_get_config {
> + le16 status;
> + le16 command_id;
> + /* generation count for the device configuration space */
> + le32 generation;
> + /* v is u8, u16, u32, or u64, then: v = (typeof v)le64_to_cpu(config) */
> + le64 config;
> +};
> +\end{lstlisting}
> +
> +\paragraph{Set Config Command}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Set Config Command}
> +The Set Config Command is used to set the device configuration space of a Virtio-oF device instance for the Virtio-oF control queue only.
> +
> +The structure of the Set Config Command structure is as follows:
> +\begin{lstlisting}
> +struct virtio_of_command_set_config {
> + /* opcode is virtio_of_op_set_config */
> + le16 opcode;
> + /* unique ID for all in-flight commands */
> + le16 command_id;
> + /* offset of device configuration space */
> + le16 offset;
> + /* bytes to get, available values: 1, 2, 4, 8 */
> + u8 bytes;
> + u8 reserved;
> + /* v is u8, u16, u32, or u64, then: config = cpu_to_le64((u64)v) */
> + le64 config;
> +};
> +\end{lstlisting}
> +
> +The structure of the Set Config Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_set_config {
> + le16 status;
> + le16 command_id;
> + u8 reserved[12];
> +};
> +\end{lstlisting}
> +
> +\paragraph{Config Change Completion}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Config Change Completion}
> +A Config Change Completion is used as a configuration change notification of a Virtio-oF device instance for the Virtio-oF control queue only.
> +Note: only a single outstanding Config Change Completion is allowed, the configuration change notification is suppressed until the Virtio-oF initiator issues a
> +\nameref{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Get Config Command}.
> +
> +The structure of the Config Change Completion is as follows:
> +\begin{lstlisting}
> +struct virtio_of_completion_config_change {
> + le16 status;
> + /* command_id is 0xfffe */
> + le16 command_id;
> + /* generation count for the device configuration space */
> + le32 generation;
> + u8 reserved[8];
> +};
> +\end{lstlisting}
> +
> +\paragraph{Keepalive Completion}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Commands Definition / Opcodes / Keepalive Completion}
> +A Keepalive Completion is used as a health check mechanism to detect when a Virtio-oF initiator becomes unavailable, it is used by a Virtio-oF device instance for the Virtio-oF control queue only.
> +Once the Virtio-oF initiator becomes unavailable, the Virtio-oF target should destroy the Virtio-oF device instance and associated resources.
> --
> 2.25.1
>
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