[xen staging] docs: update xenstore-migration.md

[patchbot@xxxxxxx]

commit 51f9df5c19f2b8a780aa2547cdf3d20736bfddcc
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Fri May 29 12:37:09 2020 +0100
Commit:     Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
CommitDate: Fri May 29 17:00:50 2020 +0100

    docs: update xenstore-migration.md
    
    Update connection record details:
    
    - make flags common for sockets and domains (makes it easier to have a
      C union for conn-spec)
    - add pending incoming data (needed for handling partially read
      requests when doing live update)
    - add partial response length (needed for proper split to individual
      responses after live update)
    
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Paul Durrant <paul@xxxxxxx>
---
 docs/designs/xenstore-migration.md | 72 ++++++++++++++++++++++----------------
 1 file changed, 41 insertions(+), 31 deletions(-)

diff --git a/docs/designs/xenstore-migration.md 
b/docs/designs/xenstore-migration.md
index 34a2afd17e..2ce2c836f5 100644
--- a/docs/designs/xenstore-migration.md
+++ b/docs/designs/xenstore-migration.md
@@ -147,43 +147,60 @@ the domain being migrated.
 ```
     0       1       2       3       4       5       6       7    octet
 +-------+-------+-------+-------+-------+-------+-------+-------+
-| conn-id                       | conn-type     | conn-spec
+| conn-id                       | conn-type     | flags         |
++-------------------------------+---------------+---------------+
+| conn-spec
 ...
-+-------------------------------+-------------------------------+
-| data-len                      | data
-+-------------------------------+
++---------------+---------------+-------------------------------+
+| in-data-len   | out-resp-len  | out-data-len                  |
++---------------+---------------+-------------------------------+
+| data
 ...
 ```
 
 
-| Field       | Description                                     |
-|-------------|-------------------------------------------------|
-| `conn-id`   | A non-zero number used to identify this         |
-|             | connection in subsequent connection-specific    |
-|             | records                                         |
-|             |                                                 |
-| `conn-type` | 0x0000: shared ring                             |
-|             | 0x0001: socket                                  |
-|             | 0x0002 - 0xFFFF: reserved for future use        |
-|             |                                                 |
-| `conn-spec` | See below                                       |
-|             |                                                 |
-| `data-len`  | The length (in octets) of any pending data not  |
-|             | yet written to the connection                   |
-|             |                                                 |
-| `data`      | Pending data (may be empty)                     |
+| Field          | Description                                  |
+|----------------|----------------------------------------------|
+| `conn-id`      | A non-zero number used to identify this      |
+|                | connection in subsequent connection-specific |
+|                | records                                      |
+|                |                                              |
+| `conn-type`    | 0x0000: shared ring                          |
+|                | 0x0001: socket                               |
+|                | 0x0002 - 0xFFFF: reserved for future use     |
+|                |                                              |
+| `flags`        | A bit-wise OR of:                            |
+|                | 0001: read-only                              |
+|                |                                              |
+| `conn-spec`    | See below                                    |
+|                |                                              |
+| `in-data-len`  | The length (in octets) of any data read      |
+|                | from the connection not yet processed        |
+|                |                                              |
+| `out-resp-len` | The length (in octets) of a partial response |
+|                | not yet written to the connection            |
+|                |                                              |
+| `out-data-len` | The length (in octets) of any pending data   |
+|                | not yet written to the connection, including |
+|                | a partial response (see `out-resp-len`)      |
+|                |                                              |
+| `data`         | Pending data: first in-data-len octets of    |
+|                | read data, then out-data-len octets of       |
+|                | written data (any of both may be empty)      |
 
-The format of `conn-spec` is dependent upon `conn-type`.
+In case of live update the connection record for the connection via which
+the live update command was issued will contain the response for the live
+update command in the pending not yet written data.
 
 \pagebreak
 
+The format of `conn-spec` is dependent upon `conn-type`.
+
 For `shared ring` connections it is as follows:
 
 
 ```
     0       1       2       3       4       5       6       7    octet
-                                                +-------+-------+
-                                                | flags         |
 +---------------+---------------+---------------+---------------+
 | domid         | tdomid        | evtchn                        |
 +-------------------------------+-------------------------------+
@@ -198,8 +215,6 @@ For `shared ring` connections it is as follows:
 |           | it has been subject to an SET_TARGET              |
 |           | operation [2] or DOMID_INVALID [3] otherwise      |
 |           |                                                   |
-| `flags`   | Must be zero                                      |
-|           |                                                   |
 | `evtchn`  | The port number of the interdomain channel used   |
 |           | by `domid` to communicate with xenstored          |
 |           |                                                   |
@@ -211,8 +226,6 @@ For `socket` connections it is as follows:
 
 
 ```
-                                                +-------+-------+
-                                                | flags         |
 +---------------+---------------+---------------+---------------+
 | socket-fd                     | pad                           |
 +-------------------------------+-------------------------------+
@@ -221,9 +234,6 @@ For `socket` connections it is as follows:
 
 | Field       | Description                                     |
 |-------------|-------------------------------------------------|
-| `flags`     | A bit-wise OR of:                               |
-|             | 0001: read-only                                 |
-|             |                                                 |
 | `socket-fd` | The file descriptor of the connected socket     |
 
 This type of connection is only relevant for live update, where the xenstored
@@ -398,4 +408,4 @@ explanation of node permissions.
 
 [3] See 
https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/include/public/xen.h;hb=HEAD#l612
 
-[4] https://wiki.xen.org/wiki/XenBus
\ No newline at end of file
+[4] https://wiki.xen.org/wiki/XenBus
--
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