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[PATCH] ccw: clarify device reset

  • 1.  [PATCH] ccw: clarify device reset

    Posted 10-11-2021 11:38
    Unlike other transports, a reset triggered by the driver is actually
    complete once the command has been completed. Make this behaviour
    and the requirements more explicit.

    Signed-off-by: Cornelia Huck <cohuck@redhat.com>
    ---

    We have discussed this before while talking about reset behaviour,
    but I don't remember sending an actual patch.

    If this looks good, I'll open an issue.

    ---
    conformance.tex | 2 ++
    content.tex | 22 +++++++++++++++++++++-
    2 files changed, 23 insertions(+), 1 deletion(-)

    diff --git a/conformance.tex b/conformance.tex
    index c52f1a40be2d..24e862ad217a 100644
    --- a/conformance.tex
    +++ b/conformance.tex
    @@ -122,6 +122,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
    \item \ref{drivernormative:Virtio Transport Options / Virtio over channel I/O / Device Initialization / Communicating Status Information}
    \item \ref{drivernormative:Virtio Transport Options / Virtio over channel I/O / Device Operation / Host->Guest Notification / Notification via Adapter I/O Interrupts}
    \item \ref{drivernormative:Virtio Transport Options / Virtio over channel I/O / Device Operation / Guest->Host Notification}
    +\item \ref{drivernormative:Virtio Transport Options / Virtio over channel I/O / Device Operation / Resetting Devices}
    \end{itemize}

    \conformance{\subsection}{Network Driver Conformance}\label{sec:Conformance / Driver Conformance / Network Driver Conformance}
    @@ -372,6 +373,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
    \item \ref{devicenormative:Virtio Transport Options / Virtio over channel I/O / Device Initialization / Setting Up Indicators / Setting Up Two-Stage Queue Indicators}
    \item \ref{devicenormative:Virtio Transport Options / Virtio over channel I/O / Device Operation / Host->Guest Notification / Notification via Adapter I/O Interrupts}
    \item \ref{devicenormative:Virtio Transport Options / Virtio over channel I/O / Device Operation / Guest->Host Notification}
    +\item \ref{devicenormative:Virtio Transport Options / Virtio over channel I/O / Device Operation / Resetting Devices}
    \end{itemize}

    \conformance{\subsection}{Network Device Conformance}\label{sec:Conformance / Device Conformance / Network Device Conformance}
    diff --git a/content.tex b/content.tex
    index 5e716721edb3..0410f46f6a78 100644
    --- a/content.tex
    +++ b/content.tex
    @@ -2775,8 +2775,28 @@ \subsubsection{Guest->Host Notification}\label{sec:Virtio Transport Options / Vi
    \subsubsection{Resetting Devices}\label{sec:Virtio Transport Options / Virtio over channel I/O / Device Operation / Resetting Devices}

    In order to reset a device, a driver sends the
    -CCW_CMD_VDEV_RESET command.
    +CCW_CMD_VDEV_RESET command. This command does not carry any payload.

    +The device signals completion of the reset operation by making the subchannel
    +status pending to indicate successful completion of the channel command.
    +Notably, the command not only triggers the reset operation, but the reset
    +operation is already completed when the operation concludes successfully.
    +
    +\devicenormative{\paragraph}{Resetting Devices}{Virtio Transport Options / Virtio over channel I/O / Device Operation / Resetting Devices}
    +
    +Before making the subchannel status pending to indicate successful completion
    +of the reset command, the device MUST reinitialize \field{device status} to
    +zero.
    +
    +The device MUST NOT send notifications or interact with the queues after
    +it signaled successful completion of the reset command.
    +
    +\drivernormative{\paragraph}{Resetting Devices}{Virtio Transport Options / Virtio over channel I/O / Device Operation / Resetting Devices}
    +
    +The driver MAY consider the reset operation to be complete already after
    +successful completion of the channel command, although it MAY also verify
    +reset completion by reading \field{device status} via CCW_CMD_READ_STATUS
    +afterwards.

    \chapter{Device Types}\label{sec:Device Types}

    --
    2.31.1