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Subject: Re: [RFC PATCH 1/5] virtio: introduce SUSPEND bit in device status
On Mon, Aug 14, 2023 at 7:29âPM Zhu Lingshan <lingshan.zhu@intel.com> wrote: > > This patch introudces 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 stablize the device states and virtqueue states. > > Its main use case is live migration. I think patch 3 needs to be squashed into this one. > > Signed-off-by: Jason Wang <jasowang@redhat.com> > Signed-off-by: Eugenio PÃrez <eperezma@redhat.com> > Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com> > --- > content.tex | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > diff --git a/content.tex b/content.tex > index 0a62dce..1bb4401 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 MUST NOT set SUSPEND if FEATURES_OK is not set. > + > +When set 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 +89,13 @@ \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. Is there any value to allow SUSPEND to be set without DRIVER_OK? > + > +The deivce MUST ignore SUSPEND if VIRTIO_F_SUSPEND is not negotiated. typo. Thanks > + > +If VIRTIO_F_SUSPEND is negotiated and SUSPEND is set, the device MUST clear SUSPEND > +and resumes operation upon DRIVER_OK. > + > \section{Feature Bits}\label{sec:Basic Facilities of a Virtio Device / Feature Bits} > > Each virtio device offers all the features it understands. During > @@ -872,6 +886,10 @@ \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(41)] 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 >
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