@@ -1,4 +1,4 @@
-#LyX 1.6.4 created this file. For more info see http://www.lyx.org/
+#LyX 1.6.5 created this file. For more info see http://www.lyx.org/
\lyxformat 345
\begin_document
\begin_header
@@ -36,8 +36,7 @@
\paperpagestyle default
\tracking_changes true
\output_changes true
-\author ""
-\author ""
+\author "Michael S. Tsirkin"
\author ""
\end_header
@@ -1441,7 +1440,28 @@ struct vring_desc {
\begin_layout Plain Layout
-#define VRING_DESC_F_WRITE 2
+#define VRING_DESC_F_WRITE 2
+\change_deleted 0 1265802057
+
+\change_inserted 0 1265802048
+
+\end_layout
+
+\begin_layout Plain Layout
+
+\change_inserted 0 1265802054
+
+/* This means the buffer contains a list of buffer descriptors.
+ */
+\end_layout
+
+\begin_layout Plain Layout
+
+\change_inserted 0 1265802049
+
+#define VRING_DESC_F_INDIRECT 4
+\change_unchanged
+
\end_layout
\begin_layout Plain Layout
@@ -1478,6 +1498,96 @@ struct vring_desc {
\begin_layout Standard
The number of descriptors in the table is specified by the Queue Size field
for this virtqueue.
+\change_deleted 0 1265801065
+
+\end_layout
+
+\begin_layout Subsubsection
+
+\change_inserted 0 1265801341
+Indirect Descriptors
+\end_layout
+
+\begin_layout Standard
+
+\change_inserted 0 1265805736
+Some devices benefit by concurrently dispatching a large number of large
+ requests.
+ To increase ring capacity it is possible to store a table of
+\emph on
+indirect descriptors
+\emph default
+ anywhere in memory, and insert a descriptor in main virtqueue (with flags&INDIRECT on) that refers to memory buffer containing this
+\emph on
+indirect descriptor table
+\emph default
+; fields
+\emph on
+addr
+\emph default
+ and
+\emph on
+len
+\emph default
+ refer to the indirect table address and length in bytes, respectively.
+ The indirect table layout structure looks like this (len is the length
+ of the descriptor that refers to this table, which is a variable, so this
+ code won't compile):
+\end_layout
+
+\begin_layout Standard
+
+\change_inserted 0 1265804397
+\begin_inset listings
+inline false
+status open
+
+\begin_layout Plain Layout
+
+\change_inserted 0 1265804526
+
+struct indirect_descriptor_table {
+\end_layout
+
+\begin_layout Plain Layout
+
+\change_inserted 0 1265804397
+
+ /* The actual descriptors (16 bytes each) */
+\end_layout
+
+\begin_layout Plain Layout
+
+\change_inserted 0 1265804473
+
+ struct vring_desc desc[len / 16];
+\end_layout
+
+\begin_layout Plain Layout
+
+\change_inserted 0 1265804397
+
+};
+\end_layout
+
+\end_inset
+
+
+\end_layout
+
+\begin_layout Standard
+
+\change_inserted 0 1265805219
+The first indirect descriptor is located at start of the indirect descriptor
+ table (index 0), additional indirect descriptors are chained by next field.
+ An indirect descriptor without next field (with flags&NEXT off) signals
+ the end of the indirect descriptor table, and transfers control back to
+ the main virtqueue.
+ An indirect descriptor can not refer to another indirect descriptor table
+ (flags&INDIRECT must be off).
+ A single indirect descriptor table can include both read-only and write-only
+ descriptors; write-only flag (flags&WRITE) in the descriptor that refers
+ to it is ignored.
\end_layout
\begin_layout Subsection
Add documentation for indirect descriptors Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- virtio-spec.lyx | 118 +++++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 files changed, 114 insertions(+), 4 deletions(-)