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Subject: [PATCH v2 1/1] virtio-pmem: Support describing pmem as shared memory region
From: Taylor Stark <tstark@microsoft.com> Update the virtio-pmem RFC spec to add support for describing the pmem region as a shared memory window. This is required to support virtio-pmem in Hyper-V, since Hyper-V only allows PCI devices to operate on memory ranges defined via BARs. When using the virtio PCI transport, shared memory regions are described via PCI BARs. Signed-off-by: Taylor Stark <tstark@microsoft.com> --- conformance.tex | 1 + virtio-pmem.tex | 30 +++++++++++++++++++++++++----- 2 files changed, 26 insertions(+), 5 deletions(-) diff --git a/conformance.tex b/conformance.tex index 33fdac9..8e414eb 100644 --- a/conformance.tex +++ b/conformance.tex @@ -201,6 +201,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} \begin{itemize} \item \ref{devicenormative:Device Types / PMEM Device / Device Initialization} +\item \ref{drivernormative:Device Types / PMEM Driver / Driver Initialization} \item \ref{drivernormative:Device Types / PMEM Driver / Driver Initialization / Direct access} \item \ref{drivernormative:Device Types / PMEM Driver / Driver Initialization / Virtio flush} \item \ref{drivernormative:Device Types / PMEM Driver / Driver Operation / Virtqueue command} diff --git a/virtio-pmem.tex b/virtio-pmem.tex index 04e07bb..9f25664 100644 --- a/virtio-pmem.tex +++ b/virtio-pmem.tex @@ -19,7 +19,10 @@ \subsection{Virtqueues}\label{sec:Device Types / PMEM Device / Virtqueues} \subsection{Feature bits}\label{sec:Device Types / PMEM Device / Feature bits} -There are currently no feature bits defined for this device. +\begin{description} +\item[VIRTIO_PMEM_F_SHMEM_REGION (0)] The guest physical address range will be +indicated as a shared memory region. +\end{description} \subsection{Device configuration layout}\label{sec:Device Types / PMEM Device / Device configuration layout} @@ -38,11 +41,11 @@ \subsection{Device configuration layout}\label{sec:Device Types / PMEM Device / \subsection{Device Initialization}\label{sec:Device Types / PMEM Device / Device Initialization} Device hotplugs physical memory to guest address space. Persistent memory device -is emulated with file backed memory at host side. - +is emulated with file backed memory at host side. The device indicates the guest +physical address to the driver in one of two ways: \begin{enumerate} -\item Guest vpmem start is read from \field{start}. -\item Guest vpmem end is read from \field{size}. +\item As a guest absolute address. +\item As a shared memory region. \end{enumerate} \devicenormative{\subsubsection}{Device Initialization}{Device Types / PMEM Device / Device Initialization} @@ -50,12 +53,29 @@ \subsection{Device Initialization}\label{sec:Device Types / PMEM Device / Device File backed memory SHOULD be memory mapped to guest address space with SHARED memory mapping. +If VIRTIO_PMEM_F_SHMEM_REGION has been negotiated, the device MUST indicate the +guest physical address as a shared memory region. The device MUST use shared +memory region ID 0. The device SHOULD set \field{start} and \field{size} to zero. + +If VIRTIO_PMEM_F_SHMEM_REGION has not been negotiated, the device MUST indicate +the guest physical address as a guest absolute address. The device MUST set +\field{start} to the absolute address and \field{size} to the size of the +address range, in bytes. + \subsection{Driver Initialization}\label{sec:Device Types / PMEM Driver / Driver Initialization} Driver hotplugs the physical memory and registers associated region with the pmem API. Also, configures a flush callback function with the corresponding region. +\drivernormative{\subsubsection}{Driver Initialization}{Device Types / PMEM Driver / Driver Initialization} + +The driver SHOULD query the physical address ranges where the pmem was mapped. +If VIRTIO_PMEM_F_SHMEM_REGION has been negotiated, the driver SHOULD query +shared memory ID 0 for the physical address ranges and MUST NOT use \field{start} +or \field{size}. Else, the driver SHOULD read the physical address ranges from +\field{start} and \field{size}. + \drivernormative{\subsubsection}{Driver Initialization: Filesystem direct access}{Device Types / PMEM Driver / Driver Initialization / Direct access} Driver SHOULD enable filesystem direct access operations for -- 2.32.0
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