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Subject: Re: [virtio-comment] Re: [RFC PATCH 1/5] virtio: introduce SUSPEND bit in device status
On Tue, Aug 15, 2023 at 6:50âPM Zhu, Lingshan <lingshan.zhu@intel.com> wrote: > > > > On 8/15/2023 8:37 AM, Jason Wang wrote: > > On Tue, Aug 15, 2023 at 8:26âAM Jason Wang <jasowang@redhat.com> wrote: > >> 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 > > Btw, it's not clear to me if driver is allowed to clear this bit. > To allow terminate a live migration process or resume from a failed live > migration, > we allow DRIVER_OK to clear SUSPEND, in patch 1. Does this imply DRIVER_OK is cleared during SUSPEND? This seems more complicated than simply allowing clearing this bit? Thanks > > Thanks > > > > 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 > >>> > > > This publicly archived list offers a means to provide input to the > OASIS Virtual I/O Device (VIRTIO) TC. > > In order to verify user consent to the Feedback License terms and > to minimize spam in the list archive, subscription is required > before posting. > > Subscribe: virtio-comment-subscribe@lists.oasis-open.org > Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org > List help: virtio-comment-help@lists.oasis-open.org > List archive: https://lists.oasis-open.org/archives/virtio-comment/ > Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf > List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists > Committee: https://www.oasis-open.org/committees/virtio/ > Join OASIS: https://www.oasis-open.org/join/ >
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