Re: [PATCH v9 09/10] admin: conformance clauses

[Jason Wang <jasowang@redhat.com>]

On Thu, Nov 24, 2022 at 5:08 AM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> Add conformance clauses for admin commands and admin virtqueues.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  admin.tex | 158 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 158 insertions(+)
>
> diff --git a/admin.tex b/admin.tex
> index eec12a9..e83a9f5 100644
> --- a/admin.tex
> +++ b/admin.tex
> @@ -222,6 +222,107 @@ \subsection{Group administration commands}\label{sec:Basic Facilities of a Virti
>  It is assumed that all members in a group support and are used
>  with the same list of commands.
>
> +\devicenormative{\paragraph}{Group administration commands}{Basic Facilities of a Virtio Device / Device groups / Group administration commands}
> +
> +The device MUST validate \field{opcode}, \field{group_type} and
> +\field{group_member_id}, set \field{status} to VIRTIO_ADMIN_STATUS_EINVAL and
> +nd if any of these has an invalid or unsupported value, set

typo

> +\field{status_qualifier} accordingly.
> +
> +If a command completes successfully, the device MUST set
> +\field{status} to VIRTIO_ADMIN_STATUS_OK.
> +
> +If a command fails, the device MUST set
> +\field{status} to a value different from VIRTIO_ADMIN_STATUS_OK.
> +
> +If \field{status} is set to VIRTIO_ADMIN_STATUS_EINVAL, the
> +device state MUST NOT change, that is the command MUST NOT have
> +any side effects on the device, in particular the device MUST not
> +enter an error state as a result of this command.
> +
> +If a command fails, the device state generally SHOULD NOT change,
> +as far as possible.
> +
> +The device MAY enforce additional restrictions and dependencies on
> +opcodes used by the driver and MAY fail the command
> +VIRTIO_ADMIN_CMD_LIST_USE with \field{status} set to VIRTIO_ADMIN_STATUS_EINVAL
> +and \field{status_qualifier} set to VIRTIO_ADMIN_STATUS_Q_INVALID_FIELD
> +if the list of commands used violate internal device dependencies.
> +
> +If the device supports multiple group types, commands for each group
> +type MUST operate independently of each other, in particular,
> +the device MAY return different results for VIRTIO_ADMIN_CMD_LIST_QUERY
> +for different group types.
> +
> +After reset, and before receiving VIRTIO_ADMIN_CMD_LIST_USE for a given group type
> +the device MUST assume
> +that the list of legal commands used by the driver consists of
> +the two commands VIRTIO_ADMIN_CMD_LIST_QUERY and VIRTIO_ADMIN_CMD_LIST_USE.
> +
> +After completing VIRTIO_ADMIN_CMD_LIST_USE successfully,
> +the device MUST set the list of legal commands used by the driver
> +to the one supplied in \field{command_specific_data}.
> +
> +The device MUST set the list of legal commands used by the driver
> +to the one supplied in VIRTIO_ADMIN_CMD_LIST_USE.
> +
> +The device MUST validate commands against the list used by
> +the driver and MUST fail any commands not in the list with
> +\field{status} set to VIRTIO_ADMIN_STATUS_EINVAL
> +and \field{status_qualifier} set to
> +VIRTIO_ADMIN_STATUS_Q_INVALID_OPCODE.
> +
> +The list of supported commands MUST NOT shrink (but MAY expand):
> +after reporting a given command as supported through
> +VIRTIO_ADMIN_CMD_LIST_QUERY the device MUST NOT later report it
> +as unsupported.  Further, after a given set of commands has been
> +used (via a successful VIRTIO_ADMIN_CMD_LIST_USE), then after a
> +device or system reset the device SHOULD complete successfully
> +any following calls to VIRTIO_ADMIN_CMD_LIST_USE with the same
> +list of commands; if this command VIRTIO_ADMIN_CMD_LIST_USE fails
> +after a device or system reset, the device MUST not fail it
> +solely because of the command list used.  Failure to do so would
> +interfere with resuming from suspend and error recovery.
> +
> +
> +\drivernormative{\paragraph}{Group administration commands}{Basic Facilities of a Virtio Device / Device groups / Group administration commands}
> +
> +The driver MAY discover whether device supports a specific group type
> +by issuing VIRTIO_ADMIN_CMD_LIST_QUERY with the matching
> +\field{group_type}.
> +
> +The driver MUST issue VIRTIO_ADMIN_CMD_LIST_USE
> +and wait for it to be completed with status
> +VIRTIO_ADMIN_STATUS_OK before issuing any commands
> +(except for the initial VIRTIO_ADMIN_CMD_LIST_QUERY
> +and VIRTIO_ADMIN_CMD_LIST_USE).
> +
> +The driver SHOULD NOT set bits in device_admin_cmds
> +if it is not familiar with how the command opcode
> +is used, as dependencies between command opcodes might exist.
> +
> +The driver MUST NOT request (via VIRTIO_ADMIN_CMD_LIST_USE)
> +the use of any commands not previously reported as
> +supported for the same group type by VIRTIO_ADMIN_CMD_LIST_QUERY.
> +
> +The driver MUST NOT use any commands for a given group type
> +before sending VIRTIO_ADMIN_CMD_LIST_USE with the correct
> +list of command opcodes and group type.
> +
> +The driver MAY block use of VIRTIO_ADMIN_CMD_LIST_QUERY and
> +VIRTIO_ADMIN_CMD_LIST_USE by issuing VIRTIO_ADMIN_CMD_LIST_USE
> +with respective bits cleared in \field{command_specific_data}.
> +
> +The driver MUST handle a command error with a reserved \field{status}
> +value in the same way as \field{status} set to VIRTIO_ADMIN_STATUS_EINVAL
> +(except possibly for different error reporting/diagnostic messages).
> +
> +The driver MUST handle a command error with a reserved
> +\field{status_qualifier} value in the same way as
> +\field{status_qualifier} set to
> +VIRTIO_ADMIN_STATUS_Q_INVALID_COMMAND (except possibly for
> +different error reporting/diagnostic messages).
> +
>  \section{Administration Virtqueues}\label{sec:Basic Facilities of a Virtio Device / Administration Virtqueues}
>
>  An administration virtqueue of an owner device is used to submit
> @@ -275,3 +376,60 @@ \section{Administration Virtqueues}\label{sec:Basic Facilities of a Virtio Devic
>  new fields can be added to the tail of a structure,
>  with the driver using the full structure without concern
>  for versioning.
> +
> +\devicenormative{\paragraph}{Group administration commands}{Basic Facilities of a Virtio Device / Administration virtqueues}
> +
> +The device MUST support device-readable and device-writeable buffers
> +shorter than described in this specification, by
> +\begin{enumerate}
> +\item assuming that any data that would be read outside the
> +device-readable buffers is set to zero, and

s/"is set"/"are set"

> +\item discarding data that would be written outside the
> +specified device-writeable buffers.
> +\end{enumerate}
> +
> +The device MUST support device-readable and device-writeable buffers
> +longer than described in this specification, by
> +\begin{enumerate}
> +\item ignoring any data in device-readable buffers outside
> +the expected length, and
> +\item only writing the expected structure to the device-writeable
> +buffers, ignoring any extra buffers, and reporting the
> +actual length of data written, in bytes,
> +as buffer used length.
> +\end{enumerate}
> +
> +The device SHOULD initialize the device-writeable buffer
> +up to the length of the structure described by this specification or
> +the length of the buffer supplied by the driver (even if the buffer is
> +all set to zero), whichever is shorter.
> +
> +The device MUST NOT fail a command solely because the buffers
> +provided are shorter or longer than described in this
> +specification.

I may miss something but how can it work if the buffer is shorter?

> +
> +The device MUST process commands on a given administration virtqueue
> +in the order in which they are queued.

Is it better to use "complete" than "process" here? Or we can reuse
part of the in-order description.

(Or maybe a flush command)

> +
> +If multiple administration virtqueues have been configured,
> +device MAY process commands on distinct virtqueues with
> +no order constraints.
> +
> +\drivernormative{\paragraph}{Group administration commands}{Basic Facilities of a Virtio Device / Administration virtqueues}
> +
> +The driver MAY supply device-readable and device-writeable buffers
> +longer than described in this specification.
> +
> +The driver SHOULD supply device-readable buffers at least as
> +large as the structure described by this specification
> +(even if the buffer is all set to zero).
> +
> +The driver MUST NOT assume that the device will initialize the whole
> +structure as described in the specification; instead,
> +the driver MUST assume that the structure
> +outside the part of the buffer used by the device
> +is set to zero.

Won't this have security implications? E.g information leak.

Thanks

> +
> +If multiple administration virtqueues have been configured,
> +the driver MUST ensure ordering for commands
> +placed on different administration virtqueues.
> --
> MST
>