From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-comment-return-708-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: From: "Dr. David Alan Gilbert (git)" Date: Wed, 20 Mar 2019 12:07:38 +0000 Message-Id: <20190320120740.8514-2-dgilbert@redhat.com> In-Reply-To: <20190320120740.8514-1-dgilbert@redhat.com> References: <20190320120740.8514-1-dgilbert@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Subject: [virtio-comment] [PATCH v4 1/3] shared memory: Define shared memory regions To: virtio-dev@lists.oasis-open.org, virtio-comment@lists.oasis-open.org Cc: stefanha@redha.com, cohuck@redhat.com List-ID: From: "Dr. David Alan Gilbert" Define the requirements and idea behind shared memory regions. Signed-off-by: Dr. David Alan Gilbert Reviewed-by: Stefan Hajnoczi --- conformance.tex | 1 + content.tex | 2 ++ shared-mem.tex | 40 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 43 insertions(+) create mode 100644 shared-mem.tex diff --git a/conformance.tex b/conformance.tex index ad7e82e..f6c0d50 100644 --- a/conformance.tex +++ b/conformance.tex @@ -195,6 +195,7 @@ A device MUST conform to the following normative statements: \item \ref{devicenormative:Basic Facilities of a Virtio Device / Virtqueues / Used Buffer Notification Suppression} \item \ref{devicenormative:Basic Facilities of a Virtio Device / Virtqueues / The Virtqueue Used Ring} \item \ref{devicenormative:Basic Facilities of a Virtio Device / Virtqueues / Available Buffer Notification Suppression} +\item \ref{devicenormative:Basic Facilities of a Virtio Device / Shared Memory Regions} \item \ref{devicenormative:Reserved Feature Bits} \end{itemize} diff --git a/content.tex b/content.tex index ede0ef6..8cd1a38 100644 --- a/content.tex +++ b/content.tex @@ -371,6 +371,8 @@ making any more buffers available. When VIRTIO_F_NOTIFICATION_DATA has been negotiated, these notifications would then have identical \field{next_off} and \field{next_wrap} values. +\input{shared-mem.tex} + \chapter{General Initialization And Device Operation}\label{sec:General Initialization And Device Operation} We start with an overview of device initialization, then expand on the diff --git a/shared-mem.tex b/shared-mem.tex new file mode 100644 index 0000000..6dc506a --- /dev/null +++ b/shared-mem.tex @@ -0,0 +1,40 @@ +\section{Shared Memory Regions}\label{sec:Basic Facilities of a Virtio Device / Shared Memory Regions} + +Shared memory regions are an additional facility +available to devices that need a region of memory that's +continuously shared between the host and the guest, rather +than passed between them in the way virtqueue elements are. + +Example uses include shared caches and version pools for versioned +data structures. + +The region is chosen by the host and presented to the guest, as +such it is useful in situations where the memory is accessed on +the host by other libraries that can't safely access guest RAM. + +A device may have multiple shared memory regions associated with +it. Each region has a \field{shmid} to identify it, the meaning +of which is device-specific. + +Enumeration and location of shared memory regions is performed +using a transport-specific data structure and mechanism. + +Memory consistency rules vary depending on the region and the +device and they will be specified as required by each device. + +\subsection{Addressing within regions}\label{sec:Basic Facilities of a Virtio Device / Shared Memory Regions / Addressing within regions } + +References into shared memory regions are represented as offsets from +the beginning of the region instead of absolute memory addresses. +Offsets are used both for references between structures stored +within shared memory and for requests placed in virtqueues that +refer to shared memory. +The \field{shmid} may be explicit or may be inferred from the +context of the reference. + +\devicenormative{\subsection}{Shared Memory Regions}{Basic Facilities of a Virtio +Device / Shared Memory Regions} +Shared memory regions MUST NOT expose shared memory regions which +are used to control the operation of the device, nor to stream +data. + -- 2.20.1 This publicly archived list offers a means to provide input to the OASIS Virtual I/O Device (VIRTIO) TC. In order to verify user consent to the Feedback License terms and to minimize spam in the list archive, subscription is required before posting. Subscribe: virtio-comment-subscribe@lists.oasis-open.org Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org List help: virtio-comment-help@lists.oasis-open.org List archive: https://lists.oasis-open.org/archives/virtio-comment/ Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists Committee: https://www.oasis-open.org/committees/virtio/ Join OASIS: https://www.oasis-open.org/join/