[virtio-dev] Re: [virtio] [PATCH v11 09/10] admin: conformance clauses

Zhu, Lingshan
2023-04-06T07:31:11Z

On 4/3/2023 11:03 PM, Michael S. Tsirkin wrote:
> Add conformance clauses for admin commands and admin virtqueues.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>
> ---
> typo and wording fixes reported by David
> clarify cmd list use can be repeated but not in parallel with other
> commands, and returning same value across uses - comment by Lingshan
> add conformance clauses for new error codes
> ---
> admin.tex | 227 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 227 insertions(+)
>
> diff --git a/admin.tex b/admin.tex
> index 9552797..a398c51 100644
> --- a/admin.tex
> +++ b/admin.tex
> @@ -283,6 +283,150 @@ \subsection{Group administration commands}\label{sec:Basic Facilities of a Virti
> supporting multiple group types, the list of supported commands
> might differ between different group types.
>
> +\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}, and if any of these has an invalid or
> +unsupported value, set \field{status} to
> +VIRTIO_ADMIN_STATUS_EINVAL and set \field{status_qualifier}
> +accordingly:
> +\begin{itemize}
> +\item if \field{group_type} is invalid, \field{status_qualifier}
> + MUST be set to VIRTIO_ADMIN_STATUS_Q_INVALID_GROUP;
> +\item otherwise, if \field{opcode} is invalid,
> + \field{status_qualifier} MUST be set to
> + VIRTIO_ADMIN_STATUS_Q_INVALID_OPCODE;
> +\item otherwise, if \field{group_member_id} is used by the
> + specific command and is invalid, \field{status_qualifier} MUST be
> + set to VIRTIO_ADMIN_STATUS_Q_INVALID_MEMBER.
> +\end{itemize}
> +
> +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, if the device supports a given group type
> +and before receiving VIRTIO_ADMIN_CMD_LIST_USE for this 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 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 reported by the device 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. Exceptions MAY apply if the system
> +configuration assures, in some way, that the driver does not
> +cache the previous value of VIRTIO_ADMIN_CMD_LIST_USE,
> +such as in the case of a firmware upgrade or downgrade.
> +
> +When processing a command with the SR-IOV group type,
> +if the device does not have an SR-IOV Extended Capability or
> +if \field{VF Enable} is clear
> +then the device MUST fail all commands with
> +\field{status} set to VIRTIO_ADMIN_STATUS_EINVAL and
> +\field{status_qualifier} set to
> +VIRTIO_ADMIN_STATUS_Q_INVALID_GROUP;
> +otherwise, if \field{group_member_id} is not
> +between $1$ and \field{NumVFs} inclusive,
> +the device MUST fail all commands with
> +\field{status} set to VIRTIO_ADMIN_STATUS_EINVAL and
> +\field{status_qualifier} set to
> +VIRTIO_ADMIN_STATUS_Q_INVALID_MEMBER;
> +\field{NumVFs}, \field{VF Migration Capable} and
> +\field{VF Enable} refer to registers within the SR-IOV Extended
> +Capability as specified by \hyperref[intro:PCIe]{[PCIe]}.
> +
> +\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 MAY issue VIRTIO_ADMIN_CMD_LIST_USE any number
> +of times but MUST NOT issue VIRTIO_ADMIN_CMD_LIST_USE commands
> +if any other command is currently being processed by the device.
Please correct me if I misunderstood this,
IMHO when the driver re-negotiates the features by issuing _USE command,
the driver can choose to shrink the feature bits and there
may be some already queued descriptors require the previous negotiated
feature bits. So I think the driver must make sure the admin queues are
empty(like all descriptors are marked as used) before it re-negotiating the
features.

Others look good to me.
> +
> +The driver SHOULD NOT set bits in device_admin_cmd_opcodes
> +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).
> +
> +When sending commands with the SR-IOV group type,
> +the driver specify a value for \field{group_member_id}
> +between $1$ and \field{NumVFs} inclusive,
> +the driver MUST also make sure that as long as any such command
> +is outstanding, \field{VF Migration Capable} is clear and
> +\field{VF Enable} is set;
> +\field{NumVFs}, \field{VF Migration Capable} and
> +\field{VF Enable} refer to registers within the SR-IOV Extended
> +Capability as specified by \hyperref[intro:PCIe]{[PCIe]}.
> +
> \section{Administration Virtqueues}\label{sec:Basic Facilities of a Virtio Device / Administration Virtqueues}
>
> An administration virtqueue of an owner device is used to submit
> @@ -357,3 +501,86 @@ \section{Administration Virtqueues}\label{sec:Basic Facilities of a Virtio Devic
> of the specification are designed, new fields can be added to the
> tail of a structure, with the driver/device 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 acting as if any data that would be read outside the
> +device-readable buffers is set to zero, and
> +\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.
> +
> +The device MUST initialize the device-writeable part of
> +\field{struct virtio_admin_cmd} that is a multiple of 64 bit in
> +size.
> +
> +The device MUST initialize \field{status} and
> +\field{status_qualifier} in \field{struct virtio_admin_cmd}.
> +
> +The device MUST process commands on a given administration virtqueue
> +in the order in which they are queued.
> +
> +If multiple administration virtqueues have been configured,
> +device MAY process commands on distinct virtqueues with
> +no order constraints.
> +
> +If the device sets \field{status} to either VIRTIO_ADMIN_STATUS_EAGAIN
> +or VIRTIO_ADMIN_STATUS_ENOMEM, then the command MUST NOT
> +have any side effects, making it safe to retry.
> +
> +\drivernormative{\paragraph}{Group administration commands}{Basic Facilities of a Virtio Device / Administration virtqueues}
> +
> +The driver MAY supply device-readable or device-writeable parts
> +of \field{struct virtio_admin_cmd} that are longer than described in
> +this specification.
> +
> +The driver SHOULD supply device-readable part of
> +\field{struct virtio_admin_cmd} that is at least as
> +large as the structure described by this specification
> +(even if the structure is all set to zero).
> +
> +The driver MUST supply both device-readable or device-writeable parts
> +of \field{struct virtio_admin_cmd} that are a multiple of 64 bit
> +in length.
> +
> +The device MUST supply both device-readable or device-writeable parts
> +of \field{struct virtio_admin_cmd} that are larger than zero in
> +length. However, \field{command_specific_data} and
> +\field{command_specific_result} MAY be zero in length, unless
> +specified otherwise for the command.
> +
> +The driver MUST NOT assume that the device will initialize the whole
> +device-writeable part of \field{struct virtio_admin_cmd} as described in the specification; instead,
> +the driver MUST act as if the structure
> +outside the part of the buffer used by the device
> +is set to zero.
> +
> +If multiple administration virtqueues have been configured,
> +the driver MUST ensure ordering for commands
> +placed on different administration virtqueues.
> +
> +The driver SHOULD retry a command that completed with
> +\field{status} VIRTIO_ADMIN_STATUS_EAGAIN.
Reviewed-by: Zhu Lingshan <lingshan.zhu@intel.com>