Re: [PATCH v9 03/10] admin: introduce group administration commands

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

On Thu, Nov 24, 2022 at 03:42:18PM +0800, Jason Wang wrote:
> On Thu, Nov 24, 2022 at 3:12 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Thu, Nov 24, 2022 at 01:52:41PM +0800, Jason Wang wrote:
> > > On Thu, Nov 24, 2022 at 5:08 AM Michael S. Tsirkin <mst@redhat.com> 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 <mgurtovoy@nvidia.com>
> > > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > > > ---
> > > >  admin.tex | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > > >  1 file changed, 98 insertions(+)
> > > >
> > > > diff --git a/admin.tex b/admin.tex
> > > > index 6ebdd05..1dca136 100644
> > > > --- a/admin.tex
> > > > +++ b/admin.tex
> > > > @@ -42,4 +42,102 @@ \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}
> > > >
> > > > +Group administration commands can be issued through an owner
> > > > +device to control member devices of a group.  This mechanism can
> > > > +be used, for example, to configure a member device before it is
> > > > +initialized by its driver.
> > >
> > > This excludes any possible runtime configuration, is this intended?
> >
> > No idea - what kind of runtime configuration are you talking about?
> > This explicitly says "to configure a member device" and that's
> > certainly at runtime.
> 
> Not sure, but if we say something like we, it means we need a group of
> commands to support runtime stuff in the future?

we'll need commands to provision members - is this what you
mean? for sure.

> >
> >
> > >
> > > > +
> > > > +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}.
> > > > +
> > > > +As a rule, 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}
> > > > +
> > > > +The \field{group_type} specifies the group type identifier.
> > >
> > > So this means there's no way for having a group specific adminq? E.g
> > > one queue for SR-IOV and another for SIOV.
> > >
> > > > +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 Linux names and error numbers:
> > >
> > > I may miss something but I don't see how it matches Linux error numbers.
> >
> >
> > include/uapi/asm-generic/errno-base.h:#define   EINVAL          22      /* Invalid argument */
> 
> Ok, only this one was matched but any advantages of menting the
> matching? I believe not all the error numbers are meaningful for a
> device interface (e.g EINTR).
> 
> Thanks

Makes it easier for driver to decide on an error to
report to userspace. If we don't use all error codes
that's fine.




> >
> >
> > > Thanks
> > >
> > > > +
> > > > +\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}
> > > > +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:
> > > > +\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_MEM    & unsupported or invalid \field{group_member_id} \\
> > > > +\hline
> > > > +0x05-0xFFFF   & -    & reserved for future use \\
> > > > +\hline
> > > > +\end{tabular}
> > > > --
> > > > MST
> > > >
> >