[virtio-dev] Re: [PATCH v11 03/10] admin: introduce group administration commands

["Zhu, Lingshan" <lingshan.zhu@intel.com>]

On 4/3/2023 11:03 PM, Michael S. Tsirkin wrote:
> This introduces a general structure for group administration commands,
> used to control device groups through their owner.
>
> Following patches will introduce specific commands and an interface for
> submitting these commands to the owner.
>
> Note that the commands are focused on controlling device groups:
> this is why group related fields are in the generic part of
> the structure.
> Without this the admin vq would become a "whatever" vq which does not do
> anything specific at all, just a general transport like thing.
> I feel going this way opens the design space to the point where
> we no longer know what belongs in e.g. config space
> what in the control q and what in the admin q.
> As it is, whatever deals with groups is in the admin q; other
> things not in the admin q.
>
> There are specific exceptions such as query but that's an exception that
> proves the rule ;)
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>
> changes since v10:
> 	explain the role of status vs status_qualifier, addresses
> 		multiple comments
> 	add more status values and appropriate qualifiers,
> 		as suggested by Parav
> 	clarify reserved command opcodes as suggested by Stefan
> 	better formatting for ranges, comment by Jiri
> 	make sure command-specific-data is a multiple of qword,
> 	so things are aligned, suggested by Jiri
> 	add Q_OK qualifier for success
> ---
>   admin.tex        | 121 +++++++++++++++++++++++++++++++++++++++++++++++
>   introduction.tex |   3 ++
>   2 files changed, 124 insertions(+)
>
> diff --git a/admin.tex b/admin.tex
> index 04d5498..c869a1a 100644
> --- a/admin.tex
> +++ b/admin.tex
> @@ -60,4 +60,125 @@ \section{Device groups}\label{sec:Basic Facilities of a Virtio Device / Device g
>   PCI transport (see \ref{sec:Virtio Transport Options / Virtio Over PCI Bus}).
>   \end{description}
>   
> +\subsection{Group administration commands}\label{sec:Basic Facilities of a Virtio Device / Device groups / Group administration commands}
>   
> +The driver sends group administration commands to the owner device of
> +a group to control member devices of the group.
> +This mechanism can
> +be used, for example, to configure a member device before it is
> +initialized by its driver.
> +\footnote{The term "administration" is intended to be interpreted
> +widely to include any kind of control. See specific commands
> +for detail.}
> +
> +All the group administration commands are of the following form:
> +
> +\begin{lstlisting}
> +struct virtio_admin_cmd {
> +        /* Device-readable part */
> +        le16 opcode;
> +        /*
> +         * 1       - SR-IOV
> +         * 2-65535 - reserved
> +         */
> +        le16 group_type;
> +        /* unused, reserved for future extensions */
> +        u8 reserved1[12];
> +        le64 group_member_id;
> +        le64 command_specific_data[];
> +
> +        /* Device-writable part */
> +        le16 status;
> +        le16 status_qualifier;
> +        /* unused, reserved for future extensions */
> +        u8 reserved2[4];
> +        u8 command_specific_result[];
> +};
> +\end{lstlisting}
> +
> +For all commands, \field{opcode}, \field{group_type} and if
> +necessary \field{group_member_id} and \field{command_specific_data} are
> +set by the driver, and the owner device sets \field{status} and if
> +needed \field{status_qualifier} and
> +\field{command_specific_result}.
> +
> +Generally, any unused device-readable fields are set to zero by the driver
> +and ignored by the device.  Any unused device-writeable fields are set to zero
> +by the device and ignored by the driver.
> +
> +\field{opcode} specifies the command. The valid
> +values for \field{opcode} can be found in the following table:
> +
> +\begin{tabular}{|l|l|}
> +\hline
> +opcode & Name & Command Description \\
> +\hline \hline
> +0x0000 - 0x7FFF & - & Commands using \field{struct virtio_admin_cmd}    \\
> +\hline
> +0x8000 - 0xFFFF & - & Reserved for future commands (possibly using a different structure)    \\
> +\hline
> +\end{tabular}
> +
> +The \field{group_type} specifies the group type identifier.
> +The \field{group_member_id} specifies the member identifier within the group.
> +See section \ref{sec:Introduction / Terminology / Device group}
> +for the definition of the group type identifier and group member
> +identifier.
> +
> +The \field{status} describes the command result and possibly
> +failure reason at an abstract level, this is appropriate for
> +forwarding to applications. The \field{status_qualifier} describes
> +failures at a low virtio specific level, as appropriate for debugging.
> +The following table describes possible \field{status} values;
> +to simplify common implementations, they are intentionally
> +matching common \hyperref[intro:errno]{Linux error names and numbers}:
> +
> +\begin{tabular}{|l|l|l|}
> +\hline
> +Status (decimal) & Name & Description \\
> +\hline \hline
> +00   & VIRTIO_ADMIN_STATUS_OK    & successful completion  \\
> +\hline
> +11   & VIRTIO_ADMIN_STATUS_EAGAIN    & try again \\
> +\hline
> +12   & VIRTIO_ADMIN_STATUS_ENOMEM    & insufficient resources \\
> +\hline
> +22   & VIRTIO_ADMIN_STATUS_EINVAL    & invalid command \\
> +\hline
> +other   & -    & group administration command error  \\
> +\hline
> +\end{tabular}
> +
> +When \field{status} is VIRTIO_ADMIN_STATUS_OK, \field{status_qualifier}
> +is reserved and set to zero by the device.
> +
> +The following table describes possible \field{status_qualifier} values:
> +\begin{tabular}{|l|l|l|}
> +\hline
> +Status & Name & Description \\
> +\hline \hline
> +0x00   & VIRTIO_ADMIN_STATUS_Q_OK               & used with VIRTIO_ADMIN_STATUS_OK  \\
> +\hline
> +0x01   & VIRTIO_ADMIN_STATUS_Q_INVALID_COMMAND  & command error: no additional information  \\
> +\hline
> +0x02   & VIRTIO_ADMIN_STATUS_Q_INVALID_OPCODE   & unsupported or invalid \field{opcode}  \\
> +\hline
> +0x03   & VIRTIO_ADMIN_STATUS_Q_INVALID_FIELD    & unsupported or invalid field within \field{command_specific_data}  \\
> +\hline
> +0x04   & VIRTIO_ADMIN_STATUS_Q_INVALID_GROUP    & unsupported or invalid \field{group_type} \\
> +\hline
> +0x05   & VIRTIO_ADMIN_STATUS_Q_INVALID_MEMBER   & unsupported or invalid \field{group_member_id} \\
> +\hline
> +0x06   & VIRTIO_ADMIN_STATUS_Q_NORESOURCE       & out of internal resources: ok to retry \\
> +\hline
> +0x07   & VIRTIO_ADMIN_STATUS_Q_TRYAGAIN         & command blocks for too long: should retry \\
> +\hline
> +0x08-0xFFFF   & -    & reserved for future use \\
> +\hline
> +\end{tabular}
> +
> +Each command uses a different \field{command_specific_data} and
> +\field{command_specific_result} structures and the length of
> +\field{command_specific_data} and \field{command_specific_result}
> +depends on these structures and is described separately or is
> +implicit in the structure description.
> diff --git a/introduction.tex b/introduction.tex
> index 287c5fc..0d849a9 100644
> --- a/introduction.tex
> +++ b/introduction.tex
> @@ -68,6 +68,9 @@ \section{Normative References}\label{sec:Normative References}
>   	\phantomsection\label{intro:FUSE}\textbf{[FUSE]} &
>   	Linux FUSE interface,
>   	\newline\url{https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/fuse.h}\\
> +	\phantomsection\label{intro:errno}\textbf{[errno]} &
> +	Linux error names and numbers,
> +	\newline\url{https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/uapi/asm-generic/errno-base.h}\\
>           \phantomsection\label{intro:eMMC}\textbf{[eMMC]} &
>           eMMC Electrical Standard (5.1), JESD84-B51,
>           \newline\url{http://www.jedec.org/sites/default/files/docs/JESD84-B51.pdf}\\
Reviewed-by: Zhu Lingshan <lingshan.zhu@intel.com>

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