This patch introduces a new status bit in the device status: SUSPEND. This SUSPEND bit can be used by the driver to suspend a device, in order to stabilize the device states and virtqueue states.
Its main use case is live migration. Signed-off-by: Zhu Lingshan <lingshan....@intel.com> Signed-off-by: Jason Wang <jasow...@redhat.com> Signed-off-by: Eugenio PĂ©rez <epere...@redhat.com> --- content.tex | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/content.tex b/content.tex index 0e492cd..0fab537 100644 --- a/content.tex +++ b/content.tex @@ -47,6 +47,9 @@ \section{\field{Device Status} Field}\label{sec:Basic Facilities of a Virtio Dev \item[DRIVER_OK (4)] Indicates that the driver is set up and ready to drive the device. +\item[SUSPEND (16)] When VIRTIO_F_SUSPEND is negotiated, indicates that the + device has been suspended by the driver. + \item[DEVICE_NEEDS_RESET (64)] Indicates that the device has experienced an error from which it can't recover. \end{description} @@ -73,6 +76,10 @@ \section{\field{Device Status} Field}\label{sec:Basic Facilities of a Virtio Dev recover by issuing a reset. \end{note} +The driver SHOULD NOT set SUSPEND if FEATURES_OK is not set. + +When setting SUSPEND, the driver MUST re-read \field{device status} to ensure the SUSPEND bit is set. + \devicenormative{\subsection}{Device Status Field}{Basic Facilities of a Virtio Device / Device Status Field} The device MUST NOT consume buffers or send any used buffer @@ -82,6 +89,26 @@ \section{\field{Device Status} Field}\label{sec:Basic Facilities of a Virtio Dev that a reset is needed. If DRIVER_OK is set, after it sets DEVICE_NEEDS_RESET, the device MUST send a device configuration change notification to the driver. +The device MUST ignore SUSPEND if FEATURES_OK is not set. + +The device MUST ignore SUSPEND if VIRTIO_F_SUSPEND is not negotiated. + +The device SHOULD allow settings to \field{device status} even when SUSPEND is set. + +If VIRTIO_F_SUSPEND is negotiated and SUSPEND is set, the device SHOULD clear SUSPEND +and resumes operation upon DRIVER_OK. + +If VIRTIO_F_SUSPEND is negotiated, when the driver sets SUSPEND, +the device SHOULD perform the following actions before presenting SUSPEND bit in the \field{device status}: + +\begin{itemize} +\item Stop consuming buffers of any virtqueues and mark all finished descritors as used. +\item Wait until all descriptors that being processed to finish and mark them as used. +\item Flush all used buffer and send used buffer notifications to the driver. +\item Record Virtqueue State of each enabled virtqueue, see section \ref{sec:Virtqueues / Virtqueue State} +\item Pause its operation except \field{device status} and preserve configurations in its Device Configuration Space, see \ref{sec:Basic Facilities of a Virtio Device / Device Configuration Space} +\end{itemize} + \section{Feature Bits}\label{sec:Basic Facilities of a Virtio Device / Feature Bits} Each virtio device offers all the features it understands. During @@ -937,6 +964,10 @@ \chapter{Reserved Feature Bits}\label{sec:Reserved Feature Bits} \ref{devicenormative:Basic Facilities of a Virtio Device / Feature Bits} for handling features reserved for future use. + \item[VIRTIO_F_SUSPEND(42)] This feature indicates that the driver can + SUSPEND the device. + See \ref{sec:Basic Facilities of a Virtio Device / Device Status Field}. + \end{description} \drivernormative{\section}{Reserved Feature Bits}{Reserved Feature Bits} -- 2.35.3 --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscr...@lists.oasis-open.org For additional commands, e-mail: virtio-dev-h...@lists.oasis-open.org