[PATCH v5 1/1] virtio-pmem: Support describing pmem as shared memory region

[tstark@linux.microsoft.com]

From: Taylor Stark <tstark@microsoft.com>

Update the virtio-pmem 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 | 14 ++++++++++++--
 virtio-pmem.tex | 40 +++++++++++++++++++++++++++++++++-------
 2 files changed, 45 insertions(+), 9 deletions(-)

diff --git a/conformance.tex b/conformance.tex
index 80547db..d9f2b45 100644
--- a/conformance.tex
+++ b/conformance.tex
@@ -31,8 +31,9 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
 \ref{sec:Conformance / Driver Conformance / Sound Driver Conformance},
 \ref{sec:Conformance / Driver Conformance / Memory Driver Conformance},
 \ref{sec:Conformance / Driver Conformance / I2C Adapter Driver Conformance},
-\ref{sec:Conformance / Driver Conformance / SCMI Driver Conformance} or
-\ref{sec:Conformance / Driver Conformance / GPIO Driver Conformance}.
+\ref{sec:Conformance / Driver Conformance / SCMI Driver Conformance},
+\ref{sec:Conformance / Driver Conformance / GPIO Driver Conformance} or
+\ref{sec:Conformance / Driver Conformance / PMEM Driver Conformance}.
 
     \item Clause \ref{sec:Conformance / Legacy Interface: Transitional Device and Transitional Driver Conformance}.
   \end{itemize}
@@ -314,6 +315,14 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
 \item \ref{drivernormative:Device Types / GPIO Device / eventq Operation}
 \end{itemize}
 
+\conformance{\subsection}{PMEM Driver Conformance}\label{sec:Conformance / Driver Conformance / PMEM Driver Conformance}
+
+A PMEM driver MUST conform to the following normative statements:
+
+\begin{itemize}
+\item \ref{drivernormative:Device Types / PMEM Device / Device Initialization}
+\end{itemize}
+
 \conformance{\section}{Device Conformance}\label{sec:Conformance / Device Conformance}
 
 A device MUST conform to the following normative statements:
@@ -578,6 +587,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
 A PMEM device MUST conform to the following normative statements:
 
 \begin{itemize}
+\item \ref{devicenormative:Device Types / PMEM Device / Device Initialization}
 \item \ref{devicenormative:Device Types / PMEM Device / Device Operation / Virtqueue flush}
 \item \ref{devicenormative:Device Types / PMEM Device / Device Operation / Virtqueue return}
 \end{itemize}
diff --git a/virtio-pmem.tex b/virtio-pmem.tex
index 93ab3c1..384eaa3 100644
--- a/virtio-pmem.tex
+++ b/virtio-pmem.tex
@@ -24,7 +24,10 @@ \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}
 
@@ -36,22 +39,45 @@ \subsection{Device configuration layout}\label{sec:Device Types / PMEM Device /
 \end{lstlisting}
 
 \begin{description}
-\item[\field{start}] contains the physical address of the first byte of the persistent memory region.
+\item[\field{start}] contains the physical address of the first byte of the
+persistent memory region, if VIRTIO_PMEM_F_SHMEM_REGION has not been negotiated.
 
-\item[\field{size}] contains the length of this address range.
+\item[\field{size}] contains the length of this address range, if
+VIRTIO_PMEM_F_SHMEM_REGION has not been negotiated.
 \end{description}
 
+\subsection{Device Initialization}\label{sec:Device Types / PMEM Device / Device Initialization}
+
+The device indicates the guest physical address to the driver in one of two ways:
 \begin{enumerate}
-\item Driver vpmem start is read from \field{start}.
-\item Driver vpmem end is read from \field{size}.
+\item As a guest absolute address, using virtio_pmem_config.
+\item As a shared memory region.
 \end{enumerate}
 
-\subsection{Driver Initialization}\label{sec:Device Types / PMEM Driver / Driver Initialization}
-
 The driver determines the start address and size of the persistent memory region in preparation for reading or writing data.
 
 The driver initializes req_vq in preparation for making flush requests.
 
+\devicenormative{\subsubsection}{Device Initialization}{Device Types / PMEM Device / Device Initialization}
+
+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.
+
+\drivernormative{\subsubsection}{Device Initialization}{Device Types / PMEM Device / Device Initialization}
+
+If VIRTIO_PMEM_F_SHMEM_REGION has been negotiated, the driver MUST query
+shared memory ID 0 for the physical address ranges, and MUST NOT use
+\field{start} or \field{stop}.
+
+If VIRTIO_PMEM_F_SHMEM_REGION has not been negotiated, the driver MUST read the
+physical address ranges from \field{start} and \field{stop}.
+
 \subsection{Driver Operations}\label{sec:Device Types / PMEM Driver / Driver Operation / Request Queues}
 
 Requests have the following format:
-- 
2.33.0.vfs.0.0