On Fri, Mar 03, 2023 at 08:13:37AM -0500, Stefan Hajnoczi wrote:
> On Thu, Mar 02, 2023 at 06:57:24PM -0500, Michael S. Tsirkin wrote:
>
> On Thu, Mar 02, 2023 at 03:10:11PM -0500, Stefan Hajnoczi wrote:
> >
> On Thu, Mar 02, 2023 at 08:05:02AM -0500, 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.
> > > >
> > >
> Signed-off-by: Max Gurtovoy <>
> > >
> Signed-off-by: Michael S. Tsirkin <>
> > > > ---
> > >
> admin.tex
| 108 +++++++++++++++++++++++++++++++++++++++++++++++
> > >
> introduction.tex |
3 ++
> > >
> 2 files changed, 111 insertions(+)
> > > >
> > >
> diff --git a/admin.tex b/admin.tex
> > >
> index 3dc47be..7e28b77 100644
> > > > --- a/admin.tex
> > > > +++ b/admin.tex
> > > > @@ -46,4 +46,112 @@ \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
> > >
> >
> I notice that the terminology is simply "the driver". "Owner driver"
> >
> and "group member driver" might be clearer because there will be two
> > > (possibly different) drivers involved.
> >
>
> Hmm I don't really want to repeat owner everywhere.
>
> I will clarify that in this section simple "driver" and "device" are
>
> owner, "member device" and "member driver" is always called explicitly.
>
> Sounds good.
>
> > > > +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;
> > > > +
u8 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 & - & Group administration commands
\\
> > > > +\hline
> > > > +0x8000 - 0xFFFF & - & Reserved
\\
> > > > +\hline
> > > > +\end{tabular}
> > >
> >
> I thought all commands are "group administration commands" but this
> >
> table makes it look like they are just a subset (0x0000 - 0x7FFF) of
> >
> group administration commands, which is a paradox.
> >
>
> Well the rest are reserved, maybe we will have more command types who
>
> knows. No?
>
> I see. Does that mean the reserved commands don't need to be in the same
> format as struct virtio_admin_cmd?
I am not good in predicting future ...
> The entire section is called "Group administration commands" but I get
> the impression it's talking both about admin virtqueue commands in
> general and specifically about group administration commands.
>
> Is it possible to structure this as follows:
>
>
Admin Commands
>
...common stuff...
>
Group Administration Commands (0x0000-0x7fff)
>
...specific to group administration commands...
>
Reserved (0x8000-0xffff)
What if I just write it like this:
> > > > +\hline \hline
> > > > +0x0000 - 0x7FFF & - & commands using struct virtio_admin_cmd
\\
> > > > +\hline
> > > > +0x8000 - 0xFFFF & - & Reserved for future commands (possibly using a different structure)
\\
will this address the comment?
> > > > +
> > > > +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 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
> > > > +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_qialifier}
> > >
> >
> s/qialifier/qualifier/
> > >
> > > > +is reserved and set to zero by the device.
> > > > +
> > > > +When \field{status} is VIRTIO_ADMIN_STATUS_EINVAL,
> > > > +the following table describes possible \field{status_qialifier} values:
> > >
> >
> s/qialifier/qualifier/
> > >
> > > > +\begin{tabular}{|l|l|l|}
> > > > +\hline
> > > > +Status & Name & Description \\
> > > > +\hline \hline
> > > > +0x00
& VIRTIO_ADMIN_STATUS_Q_INVALID_COMMAND
& command error: no additional information \\
> > > > +\hline
> > > > +0x01
& VIRTIO_ADMIN_STATUS_Q_INVALID_OPCODE
& unsupported or invalid \field{opcode} \\
> > > > +\hline
> > > > +0x02
& VIRTIO_ADMIN_STATUS_Q_INVALID_FIELD
& unsupported or invalid field within \field{command_specific_data} \\
> > > > +\hline
> > > > +0x03
& VIRTIO_ADMIN_STATUS_Q_INVALID_GROUP
& unsupported or invalid \field{group_type} \\
> > > > +\hline
> > > > +0x04
& VIRTIO_ADMIN_STATUS_Q_INVALID_MEMBER
& unsupported or invalid \field{group_member_id} \\
> > > > +\hline
> > > > +0x05-0xFFFF
& -
& 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.
> > >
> >
> On more thing:
> > >
> >
> Does the owner device see commands in order but may complete them in any
> >
> order?
> > >
> >
> I think this information might be useful just to make it clear that
> >
> driver authors shouldn't make assumptions about ordering and completion
> >
> order, e.g. pipelining a bunch of dependent commands doesn't work
> >
> because the first command is not necessarily completed before the second
> >
> command is started.
> >
>
> I think this is discussed when we discuss sending commands through vq.
>
> in this section it's just about commands generally whatever the way
>
> to send them to device. no?
>
> Okay. I'm reading this patch series linearly and the question popped
> into my mind here. Glad it's already covered elsewhere.
>
> Stefan
