Re: [PATCH RFC v7 2/8] Introduce group administration commands

[Jason Wang <jasowang@redhat.com>]

On Sat, Aug 13, 2022 at 1:19 AM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> From: Max Gurtovoy <mgurtovoy@nvidia.com>
>
> These commands are used for essential administrative and management
> operations.
>
> Following patches will introduce an interface for submitting these
> commands to the device.
>
> Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  admin.tex | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 94 insertions(+), 5 deletions(-)
>
> diff --git a/admin.tex b/admin.tex
> index 6e9434a..4840dd4 100644
> --- a/admin.tex
> +++ b/admin.tex
> @@ -9,8 +9,10 @@ \section{Device groups}\label{sec:Basic Facilities of a Virtio Device / Device g
>  \item[Parent device]
>          or parent, the device controlling the group.
>  \item[Member device]
> -        a device within a group. Parent device itself may, or may
> -       not be a member of the group.
> +        a device within a group. Parent device itself is not
> +       a member of the group. In the future it is envisoned that
> +       new group types may be introduced where the parent
> +       device is a member of the group.

This part should go with patch 1?

>  \item[Member identifier]
>          each member has this indentifier, unique within the group
>         and used to address it through the parent device.
> @@ -20,9 +22,10 @@ \section{Device groups}\label{sec:Basic Facilities of a Virtio Device / Device g
>         and what kind of control does the parent have.
>  \item[Group identifier]
>         each group has this identifier, unique within the parent device.
> -       this specifies the group type and possibly selects the
> -       group if multiple groups of the same type can be controlled by the same
> -       parent device.
> +       This specifies the group type. In the future it is
> +       envisoned that new group types will be introduced where the group
> +       identifier also selects the group if multiple groups of the same
> +       type can be controlled by the same parent device.
>  \end{description}
>
>  A single group type is currently specified:
> @@ -46,4 +49,90 @@ \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 / Group administration commands}
> +
> +Group administration commands can be issued through a parent
> +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.
> +
> +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_id;

I wonder about the implication of this field. Does it mean:

1) a single admin virtqueue that manage two group of VFs

or

2) a single admin virtqueue that manages both VFs and SFs (then
'group_type' should be better?)

If it's 1, the group id seems not sufficient. If it's 2, I wonder if
it scales (using a single admin virtqueue to manage both VF and SF).

Thanks

> +        /* unused, reserved for future extensions */
> +        u8 reserved1[12];
> +        le64 group_member_id;
> +        u8 command_specific_data[];
> +
> +        /* Device-writable part */
> +        u8 status;
> +        u8 command_specific_error;
> +        /* unused, reserved for future extensions */
> +        u8 reserved2[6];
> +        u8 command_specific_result[];
> +};
> +\end{lstlisting}
> +
> +For all commands, \field{opcode}, \field{group_id} and if
> +necessary \field{group_member_id} and \field{command_specific_data} are
> +set by the driver, and the parent device sets \field{status} and if
> +needed \field{command_specific_error} 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 & Command Description \\
> +\hline \hline
> +0000h - 7FFFh   & Group administration commands    \\
> +\hline
> +8000h - FFFFh   & Reserved    \\
> +\hline
> +\end{tabular}
> +
> +The \field{group_id} specifies the device group.
> +The \field{group_member_id} specifies the member device within the group.
> +See section \ref{sec:Introduction / Terminology / Device group}
> +for the definition of the group identifier and group member
> +identifier.
> +
> +The following table describes possible \field{status} values:
> +
> +\begin{tabular}{|l|l|l|}
> +\hline
> +Status & Name & Description \\
> +\hline \hline
> +00h   & VIRTIO_ADMIN_STATUS_OK    & successful completion  \\
> +\hline
> +01h   & VIRTIO_ADMIN_STATUS_CS_ERR    & command specific error  \\
> +\hline
> +02h   & VIRTIO_ADMIN_STATUS_OPCODE_UNSUPPORTED    & unsupported or invalid \field{opcode}  \\
> +\hline
> +03h   & VIRTIO_ADMIN_STATUS_INVALID_FIELD    & invalid field within command specific data  \\
> +\hline
> +04h   & VIRTIO_ADMIN_STATUS_INVALID_GROUP    & invalid group identifier was set  \\
> +\hline
> +05h   & VIRTIO_ADMIN_STATUS_INVALID_MEM    & invalid group member identifier was set  \\
> +\hline
> +\end{tabular}
> +
> +The \field{command_specific_error} should be inspected by the driver only if \field{status} is set to
> +VIRTIO_ADMIN_STATUS_CS_ERR by the device. In this case, the
> +contents of \field{command_specific_error}
> +holds the command specific error. If \field{status} is not set to VIRTIO_ADMIN_STATUS_CS_ERR, the
> +\field{command_specific_error} value is undefined and should be ignored by the driver.
>
> --
> MST
>