[virtio-dev] Re: [PATCH v12 03/10] admin: introduce group administration commands

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Apr 25, 2023 at 12:29:02AM +0300, Max Gurtovoy wrote:
> 
> 
> On 24/04/2023 19:44, 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>
> > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> > Reviewed-by: Zhu Lingshan <lingshan.zhu@intel.com>
> > ---
> > 
> > changes since v11:
> > 	acks by Stefan and Lingshan
> > 
> > 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 05d506a..d6042e4 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.
> > +
> 
> actually it is:
> 
> When \field{status} is VIRTIO_ADMIN_STATUS_OK, \field{status_qualifier}
> can be ignored by driver and set to VIRTIO_ADMIN_STATUS_Q_OK by the device.

ok though it's mostly the same, VIRTIO_ADMIN_STATUS_Q_OK is 0 ...

> Can be moved after the status_qualifier values paragraph.
> 
> 
> > +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}
> 
> should we mention which status_qualifier can match to which status (as we
> did for STATUS_OK) ?

conformance clauses do this.

> > +
> > +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..b7155bf 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/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}\\


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