[virtio-comment] [PATCH v2 05/11] transport-fabrics: introduce Keyed Transmission

[zhenwei pi <pizhenwei@bytedance.com>]

Keyed transmission is used for message oriented communication(Ex RDMA),
also add virtio-blk read/write 8K example.

Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
---
 transport-fabrics.tex | 178 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 178 insertions(+)

diff --git a/transport-fabrics.tex b/transport-fabrics.tex
index c02cf26..7711321 100644
--- a/transport-fabrics.tex
+++ b/transport-fabrics.tex
@@ -317,3 +317,181 @@ \subsubsection{Buffer Mapping Definition}\label{sec:Virtio Transport Options / V
                     |......|
                     +------+  -> 8193
 \end{lstlisting}
+
+\paragraph{Keyed Transmission}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Transmission Protocol / Commands Definition / Keyed Transmission}
+Command and Segment Descriptors are transmitted in a message within a
+connection, and buffer is transmitted by remote memory access.  The layout in message:
+
+\begin{lstlisting}
+CMDx contains 0 descriptor, CMDy contains (n - m + 1) descriptors:
+
+     +-----+     +-----++-----+     +-----+
+ ... | CMDx| ... | CMDy||DESCm| ... |DESCn| ...
+     +-----+     +-----++-----+     +-----+
+
+COMPx contains 0 descriptor, COMPy contains 0 descriptor:
+
+     +-----+     +-----+
+ ... |COMPx| ... |COMPy| ...
+     +-----+     +-----+
+\end{lstlisting}
+
+An example of a virtio-blk write 8K request(message size: sizeof(Command) +
+4 * sizeof(Descriptor)):
+\begin{lstlisting}
+ COMMAND            +------+
+                    |opcode|  ->  virtio_of_op_vring
+                    +------+
+                    |cmd id|  ->  10
+                    +------+
+                    |length|  ->  0
+                    +------+
+                    |ndesc |  ->  4
+                    +------+
+                    |rsvd  |
+                    +------+
+
+ DESC0              +------+
+                    |addr  |  -> 0xffff012345670000
+                    +------+
+                    |length|  -> 16 (virtio blk write command)
+                    +------+
+                    |id    |  -> 0
+                    +------+
+                    |flags |  -> VIRTIO_OF_DESC_F_KEYED
+                    +------+
+                    |key   |  -> 0x1234
+                    +------+
+
+ DESC1              +------+
+                    |addr  |  -> 0xffff012345671000
+                    +------+
+                    |length|  -> 4096
+                    +------+
+                    |id    |  -> 1
+                    +------+
+                    |flags |  -> VIRTIO_OF_DESC_F_KEYED
+                    +------+
+                    |key   |  -> 0x1236
+                    +------+
+
+ DESC2              +------+
+                    |addr  |  -> 0xffff012345673000
+                    +------+
+                    |length|  -> 4096
+                    +------+
+                    |id    |  -> 2
+                    +------+
+                    |flags |  -> VIRTIO_OF_DESC_F_KEYED
+                    +------+
+                    |key   |  -> 0x1238
+                    +------+
+
+ DESC3              +------+
+                    |addr  |  -> 0xffff012345677000
+                    +------+
+                    |length|  -> 1
+                    +------+
+                    |id    |  -> 3
+                    +------+
+                    |flags |  -> VIRTIO_OF_DESC_F_KEYED | VIRTIO_OF_DESC_F_WRITE
+                    +------+
+                    |key   |  -> 0x1239
+                    +------+
+\end{lstlisting}
+
+The target handles Command, reads the remote addresses of DESC0/DESC1/DESC2,
+writes the remote address of DESC3, then responses Completion:
+\begin{lstlisting}
+ COMPLETION         +------+
+                    |status|  ->  VIRTIO_OF_SUCCESS
+                    +------+
+                    |cmd id|  ->  10
+                    +------+
+                    |ndesc |  ->  0
+                    +------+
+                    |rsvd  |
+                    +------+
+                    |value |  -> 1 (value.u32)
+                    +------+
+\end{lstlisting}
+
+Another example of a virtio-blk read 8K request(message size: sizeof(Command) +
+4 * sizeof(Descriptor)):
+\begin{lstlisting}
+ COMMAND            +------+
+                    |opcode|  ->  virtio_of_op_vring
+                    +------+
+                    |cmd id|  ->  10
+                    +------+
+                    |length|  ->  0
+                    +------+
+                    |ndesc |  ->  4
+                    +------+
+                    |rsvd  |
+                    +------+
+
+ DESC0              +------+
+                    |addr  |  -> 0xffff012345670000
+                    +------+
+                    |length|  -> 16 (virtio blk write command)
+                    +------+
+                    |id    |  -> 0
+                    +------+
+                    |flags |  -> VIRTIO_OF_DESC_F_KEYED
+                    +------+
+                    |key   |  -> 0x1234
+                    +------+
+
+ DESC1              +------+
+                    |addr  |  -> 0xffff012345671000
+                    +------+
+                    |length|  -> 4096
+                    +------+
+                    |id    |  -> 1
+                    +------+
+                    |flags |  -> VIRTIO_OF_DESC_F_KEYED | VIRTIO_OF_DESC_F_WRITE
+                    +------+
+                    |key   |  -> 0x1236
+                    +------+
+
+ DESC2              +------+
+                    |addr  |  -> 0xffff012345673000
+                    +------+
+                    |length|  -> 4096
+                    +------+
+                    |id    |  -> 2
+                    +------+
+                    |flags |  -> VIRTIO_OF_DESC_F_KEYED | VIRTIO_OF_DESC_F_WRITE
+                    +------+
+                    |key   |  -> 0x1238
+                    +------+
+
+ DESC3              +------+
+                    |addr  |  -> 0xffff012345677000
+                    +------+
+                    |length|  -> 1
+                    +------+
+                    |id    |  -> 3
+                    +------+
+                    |flags |  -> VIRTIO_OF_DESC_F_KEYED | VIRTIO_OF_DESC_F_WRITE
+                    +------+
+                    |key   |  -> 0x1239
+                    +------+
+\end{lstlisting}
+
+The target handles Command, reads the remote address of DESC0, writes the remote
+addresses of DESC1/DESC2/DESC3, then responses Completion:
+\begin{lstlisting}
+ COMPLETION         +------+
+                    |status|  ->  VIRTIO_OF_SUCCESS
+                    +------+
+                    |cmd id|  ->  10
+                    +------+
+                    |ndesc |  ->  0
+                    +------+
+                    |rsvd  |
+                    +------+
+                    |value |  -> 8193 (value.u32)
+                    +------+
+\end{lstlisting}
-- 
2.25.1


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