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Subject: Re: [PATCH V2 2/6] virtio: introduce SUSPEND bit in device status
On 11/3/2023 7:35 PM, Parav Pandit wrote:
From: Zhu Lingshan <lingshan.zhu@intel.com> Sent: Friday, November 3, 2023 4:05 PM 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.zhu@intel.com> Signed-off-by: Jason Wang <jasowang@redhat.com>You constantly complained that whatever was proposed using admin commands method in [1] must work for passthrough and non-passthrough. And halfway in the discussion you propose a method after learning all the limitations of in-band, you propose a solution only works for non-passthrough mode. You asked someone to have comprehensive proposal and when it comes to you following it, you just donât.
not sure what you are talking about.
this SUSPEND/RESUME doesn't change since the RFC series, how can it not be inconsistent???And have most shallow commit message to not even mention it. Please be consistent in design approach. And if you donât want to be, stop asking others.
This is not the way TC collaboration works. I probably shouldnât even expect this from you. [1] https://lists.oasis-open.org/archives/virtio-comment/202310/msg00472.html
Please don't be so emotional and please be professional.Why this solution can not work for pass-through? Do you know the device ownership will be transferred to the hypervisor when guest suspended in live migration?
Signed-off-by: Eugenio PÃrez <eperezma@redhat.com> --- content.tex | 36 ++++++++++++++++++++++++++++++++++-- 1 file changed, 34 insertions(+), 2 deletions(-) diff --git a/content.tex b/content.tex index 76813b5..bcc9d4b 100644 --- a/content.tex +++ b/content.tex @@ -49,6 +49,10 @@ \section{\field{Device Status} Field}\label{sec:Basic Facilities of a Virtio Dev \item[DEVICE_NEEDS_RESET (64)] Indicates that the device has experienced an error from which it can't recover. + +\item[SUSPEND (16)] When VIRTIO_F_SUSPEND is negotiated, indicates that +the + device has been suspended by the driver. + \end{description} The \field{device status} field starts out as 0, and is reinitialized to 0 by @@ - 73,6 +77,10 @@ \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 +90,26 @@ \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 @@ -99,10 +127,10 @@ \section{Feature Bits}\label{sec:Basic Facilities of a Virtio Device / Feature B \begin{description} \item[0 to 23, and 50 to 127] Feature bits for the specific device type -\item[24 to 42] Feature bits reserved for extensions to the queue and +\item[24 to 43] Feature bits reserved for extensions to the queue and feature negotiation mechanisms -\item[43 to 49, and 128 and above] Feature bits reserved for future extensions. +\item[44 to 49, and 128 and above] Feature bits reserved for future extensions. \end{description} \begin{note} @@ -875,6 +903,10 @@ \chapter{Reserved Feature Bits}\label{sec:Reserved Feature Bits} \item[VIRTIO_F_QUEUE_STATE(42)] This feature indicates that the device allows the driver to access its internal virtqueue state. + \item[VIRTIO_F_SUSPEND(43)] 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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