On 8/16/2023 10:05 AM, Jason Wang wrote:
On Tue, Aug 15, 2023 at 6:50 PM Zhu, Lingshan<lingshan....@intel.com> wrote:
On 8/15/2023 8:37 AM, Jason Wang wrote:
On Tue, Aug 15, 2023 at 8:26 AM Jason Wang<jasow...@redhat.com> wrote:
On Mon, Aug 14, 2023 at 7:29 PM Zhu Lingshan<lingshan....@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<jasow...@redhat.com>
Signed-off-by: Eugenio PÃrez<epere...@redhat.com>
Signed-off-by: Zhu Lingshan<lingshan....@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?
No, SUSPEND does not clears DRIVER_OK, only DRIVER_OK clears SUSPEND.
The spec says: The driver MUST NOT clear a device status bit.
So I think maybe it's better let the device clears SUSPEND.
Thanks
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
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