[PATCH V2 5/6] virtio: introduce dirty page tracking facility

[Zhu Lingshan <lingshan.zhu@intel.com>]

This commit introduce a new virtio facility to track
device dirty pages, a typical use case is live migration.

The implementation of this facility is transport specific.

Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Eugenio PÃrez <eperezma@redhat.com>
---
 content.tex | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/content.tex b/content.tex
index 060b5c2..eb9274f 100644
--- a/content.tex
+++ b/content.tex
@@ -127,10 +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 43] Feature bits reserved for extensions to the queue and
+\item[24 to 44] Feature bits reserved for extensions to the queue and
   feature negotiation mechanisms
 
-\item[44 to 49, and 128 and above] Feature bits reserved for future extensions.
+\item[45 to 49, and 128 and above] Feature bits reserved for future extensions.
 \end{description}
 
 \begin{note}
@@ -535,6 +535,27 @@ \section{Exporting Objects}\label{sec:Basic Facilities of a Virtio Device / Expo
 
 \input{admin.tex}
 
+\section{Memory Dirty Pages Tracker}\label{sec:Basic Facilities of a Virtio Device / Memory Dirty Pages Tracker}
+
+A "dirty page" refers to a page in memory that has been modified by the device
+but have not yet been acknowledged or processed by the CPU.
+
+This Memory Dirty Pages Tracker is a device facility that can record and report
+dirty pages caused by the device in device address space.
+
+The device offers a feature bit VIRTIO_F_MEM_TRACK if capable of tracking dirty pages.
+The implementation of this dirty page tracking facility is transport specific.
+
+A typical use case of this facility is to track dirty pages during live migration process.
+
+\drivernormative{\subsection}{Memory Dirty Pages Tracker}{Facilities of a Virtio Device / Memory Dirty Pages Tracker}
+
+The driver MUST fetch and clear dirty page information atomically.
+
+\devicenormative{\subsection}{Memory Dirty Pages Tracker}{Facilities of a Virtio Device / Memory Dirty Pages Tracker}
+
+The device MUST report the dirty page information atomically.
+
 \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
@@ -910,6 +931,9 @@ \chapter{Reserved Feature Bits}\label{sec:Reserved Feature Bits}
    SUSPEND the device.
    See \ref{sec:Basic Facilities of a Virtio Device / Device Status Field}.
 
+  \item[VIRTIO_F_MEM_TRACK(44)] This feature indicates that the device can track
+  memory dirty pages caused by itself.
+
 \end{description}
 
 \drivernormative{\section}{Reserved Feature Bits}{Reserved Feature Bits}
-- 
2.35.3