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Subject: Re: [virtio-comment] Re: [PATCH v1 3/8] device-context: Define the device context fields for device migration
On 10/8/2023 7:41 PM, Michael S. Tsirkin wrote:
On Sun, Oct 08, 2023 at 02:25:50PM +0300, Parav Pandit wrote:Define the device context and its fields for purpose of device migration. The device context is read and written by the owner driver on source and destination hypervisor respectively. Device context fields will experience a rapid growth post this initial version to cover many details of the device. Fixes: https://github.com/oasis-tcs/virtio-spec/issues/176 Signed-off-by: Parav Pandit <parav@nvidia.com> Signed-off-by: Satananda Burla <sburla@marvell.com> --- changelog: v0->v1: - enrich device context to cover feature bits, device configuration fields - corrected alignment of device context fields --- content.tex | 1 + device-context.tex | 142 +++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 143 insertions(+) create mode 100644 device-context.tex diff --git a/content.tex b/content.tex index 0a62dce..2698931 100644 --- a/content.tex +++ b/content.tex @@ -503,6 +503,7 @@ \section{Exporting Objects}\label{sec:Basic Facilities of a Virtio Device / Expo UUIDs as specified by \hyperref[intro:rfc4122]{[RFC4122]}.\input{admin.tex}+\input{device-context.tex}\chapter{General Initialization And Device Operation}\label{sec:General Initialization And Device Operation} diff --git a/device-context.tex b/device-context.texnew file mode 100644 index 0000000..5611382 --- /dev/null +++ b/device-context.tex @@ -0,0 +1,142 @@ +\section{Device Context}\label{sec:Basic Facilities of a Virtio Device / Device Context} + +The device context holds the information that a owner driver can use +to setup a member device and resume its operation. The device context +of a member device is read or written by the owner driver using +administration commands. + +\begin{lstlisting} +struct virtio_dev_ctx_field_tlv { + le32 type; + le32 reserved; + le64 length; + u8 value[]; +}; + +struct virtio_dev_ctx { + le32 field_count; + struct virtio_dev_ctx_field_tlv fields[]; +}; + +\end{lstlisting}
so this still doesn't work for nested
+ +The \field{struct virtio_dev_ctx} is the device context of a member device. +The \field{field_count} indicates how many instances of +\field{struct virtio_dev_ctx_field_tlv} are present. + +The \field{struct virtio_dev_ctx_field_tlv} consist of \field{type} indicating +what data is contained in the \field{value} of length \field{length}. +The valid values for \field{type} can be found in the following table: + +\begin{tabularx}{\textwidth}{ |l||l|X| } +\hline +type & Name & Description \\ +\hline \hline +0x0 & VIRTIO_DEV_CTX_PCI_COMMON_RUNTIME_CFG & Provides common configuration space of device for PCI transport \\ +\hline +0x1 & VIRTIO_DEV_CTX_DEV_CFG_LAYOUT & Provides device specific configuration layout \\ +\hline +0x2 & VIRTIO_DEV_CTX_DEV_FEATURES & Provides device features \\ +\hline +0x3 & VIRTIO_DEV_CTX_PCI_VQ_CFG & Provides Virtqueue configuration for PCI transport \\ +\hline +0x4 & VIRTIO_DEV_CTX_VQ_SPLIT_RUNTIME_CFG & Provides Queue run time state \\ +\hline +0x5 & VIRTIO_DEV_CTX_VQ_SPLIT_DEV_OWN_DESC & Provides list of virtqueue descriptors owned by device \\ +\hline +0x6 - 0xFFFFFFFF & - & Reserved for future types \\ +\hline +\end{tabularx}I don't think this is enough, e.g. virtio net has internal state controlled thought CVQ commands. how do you intend to address/migrate these?+\subsubsection{Device Context Fields}\label{sec:Basic Facilities of a Virtio Device / Device Context / Device Context Fields} + +\paragraph{PCI Common Configuration Context} +\label{par:Basic Facilities of a Virtio Device / Device Context / Device Context Fields/ PCI Common Configuration Context} + +For the field VIRTIO_DEV_CTX_PCI_COMMON_RUNTIME_CFG, \field{type} is set to 0x0. +The \field{value} is in format of \field{struct virtio_pci_common_cfg}. +The \field{length} is the length of \field{struct virtio_pci_common_cfg}. + +\paragraph{Device Configuration Layout Context} +\label{par:Basic Facilities of a Virtio Device / Device Context / Device Context Fields/ Device Configuration Layout Context} + +For the field VIRTIO_DEV_CTX_DEV_CFG_LAYOUT, \field{type} is set to 0x1. +The \field{value} is in format of device specific configuration layout listed +in each of the device's device configuration layout section. +The \field{length} is the length of the device configuration layout data.Unclear. I am guessing it's doing things like setting up RO fields? This needs to be specified per device really. Also how some fields behave might depend on features.+ +\paragraph{Device Features Context} +\label{par:Basic Facilities of a Virtio Device / Device Context / Device Context Fields/ Device Features Context} + +For the field VIRTIO_DEV_CTX_DEV_FEATURES, \field{type} is set to 0x2. +The \field{value} is in format of device feature bits listed in +\ref{sec:Basic Facilities of a Virtio Device / Feature Bits} in the format of \field{struct virtio_dev_ctx_features}. +The \field{length} is the length of the device features. + +\begin{lstlisting} +struct virtio_dev_ctx_pci_vq_cfg { + le64 feature_bits[]; +}; +\end{lstlisting} + +\paragraph{PCI Virtqueue Configuration Context} +\label{par:Basic Facilities of a Virtio Device / Device Context / Device Context Fields/ PCI Virtqueue Configuration Context} + +For the field VIRTIO_DEV_CTX_PCI_VQ_CFG, \field{type} is set to 0x3. +The \field{value} is in format of \field{struct virtio_dev_ctx_pci_vq_cfg}. +The \field{length} is the length of \field{struct virtio_dev_ctx_pci_vq_cfg}. + +\begin{lstlisting} +struct virtio_dev_ctx_pci_vq_cfg { + le16 vq_index; + le16 queue_size; + le16 queue_msix_vector; + le64 queue_descÍ + le64 queue_driverÍ + le64 queue_deviceÍ +}; +\end{lstlisting} + +One or multiple entries of PCI Virtqueue Configuration Context may exist, each such +entry corresponds to a unique virtqueue identified by the \field{vq_index}. + +\paragraph{Virtqueue Split Mode Runtime Context} +\label{par:Basic Facilities of a Virtio Device / Device Context / Device Context Fields/ Virtqueue Split Mode Runtime Context} + +For the field VIRTIO_DEV_CTX_VQ_SPLIT_RUNTIME_CFG, \field{type} is set to 0x4. +The \field{value} is in format of \field{struct virtio_dev_ctx_vq_split_runtime}. +The \field{length} is the length of \field{struct virtio_dev_ctx_vq_split_runtime}. + +\begin{lstlisting} +struct virtio_dev_ctx_vq_split_runtime { + le16 vq_index; + le16 dev_avail_idx; + u8 enabled; +}; +\end{lstlisting} + +The \field{dev_avail_idx} indicates the next available index of the virtqueue from which +the device must start processing the available ring. + +One or multiple entries of Virtqueue Split Mode Runtime Context may exist, each such +entry corresponds to a unique virtqueue identified by the \field{vq_index}. + +\paragraph{Virtqueue Split Mode Device owned Descriptors Context} + +For the field VIRTIO_DEV_CTX_VQ_SPLIT_DEV_OWN_DESC, \field{type} is set to 0x5. +The \field{value} is in format of \field{struct virtio_dev_ctx_vq_split_runtime}. +The \field{length} is the length of \field{struct virtio_dev_ctx_vq_split_dev_descs}. + +\begin{lstlisting} +struct virtio_dev_ctx_vq_split_dev_descs { + le16 vq_index; + le16 desc_count; + le16 desc_idx[]; +}; +\end{lstlisting} + +The \field{desc_idx} contains indices of the descriptors in \field{desc_count} of a +virtqueue identified by \field{vq_index} which is owned by the device. + +One or multiple entries of Virtqueue Split Mode Device owned Descriptors Context may exist, each such +entry corresponds to a unique virtqueue identified by the \field{vq_index}. -- 2.34.1This publicly archived list offers a means to provide input to the OASIS Virtual I/O Device (VIRTIO) TC. 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