[xen master] docs: update the xenstore migration stream documentation

[patchbot@xxxxxxx]

commit 8868a0e3f67436a5fbee750624e24a6533357f52
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Fri Jan 15 09:29:48 2021 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Jan 15 11:44:47 2021 +0000

    docs: update the xenstore migration stream documentation
    
    For live update of Xenstore some records defined in the migration
    stream document need to be changed:
    
    - Support of the read-only socket has been dropped from all Xenstore
      implementations, so ro-socket-fd in the global record can be removed.
    
    - Some guests require the event channel to Xenstore to remain the same
      on Xenstore side, so Xenstore has to keep the event channel interface
      open across a live update. For this purpose an evtchn-fd needs to be
      added to the global record.
    
    - With no read-only support the flags field in the connection record
      can be dropped.
    
    - The evtchn field in the connection record needs to be switched to
      hold the port of the Xenstore side of the event channel.
    
    - A flags field needs to be added to permission specifiers in order to
      be able to mark a permission as stale (XSA-322).
    
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 docs/designs/xenstore-migration.md | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/docs/designs/xenstore-migration.md 
b/docs/designs/xenstore-migration.md
index 2ce2c836f5..1a5b94b31d 100644
--- a/docs/designs/xenstore-migration.md
+++ b/docs/designs/xenstore-migration.md
@@ -116,7 +116,7 @@ xenstored state that needs to be restored.
 +-------+-------+-------+-------+
 | rw-socket-fd                  |
 +-------------------------------+
-| ro-socket-fd                  |
+| evtchn-fd                     |
 +-------------------------------+
 ```
 
@@ -126,8 +126,8 @@ xenstored state that needs to be restored.
 | `rw-socket-fd` | The file descriptor of the socket accepting  |
 |                | read-write connections                       |
 |                |                                              |
-| `ro-socket-fd` | The file descriptor of the socket accepting  |
-|                | read-only connections                        |
+| `evtchn-fd`    | The file descriptor used to communicate with |
+|                | the event channel driver                     |
 
 xenstored will resume in the original process context. Hence `rw-socket-fd` and
 `ro-socket-fd` simply specify the file descriptors of the sockets. Sockets
@@ -147,7 +147,7 @@ the domain being migrated.
 ```
     0       1       2       3       4       5       6       7    octet
 +-------+-------+-------+-------+-------+-------+-------+-------+
-| conn-id                       | conn-type     | flags         |
+| conn-id                       | conn-type     |               |
 +-------------------------------+---------------+---------------+
 | conn-spec
 ...
@@ -169,9 +169,6 @@ the domain being migrated.
 |                | 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      |
@@ -216,7 +213,7 @@ For `shared ring` connections it is as follows:
 |           | operation [2] or DOMID_INVALID [3] otherwise      |
 |           |                                                   |
 | `evtchn`  | The port number of the interdomain channel used   |
-|           | by `domid` to communicate with xenstored          |
+|           | by xenstored to communicate with `domid`          |
 |           |                                                   |
 
 Since the ABI guarantees that entry 1 in `domid`'s grant table will always
@@ -386,7 +383,7 @@ A node permission specifier has the following format:
 ```
     0       1       2       3    octet
 +-------+-------+-------+-------+
-| perm  | pad   | domid         |
+| perm  | flags | domid         |
 +-------+-------+---------------+
 ```
 
@@ -395,6 +392,10 @@ A node permission specifier has the following format:
 | `perm`  | One of the ASCII values `w`, `r`, `b` or `n` as     |
 |         | specified for the `SET_PERMS` operation [2]         |
 |         |                                                     |
+| `flags` | A bit-wise OR of:                                   |
+|         | 0x01: stale permission, ignore when checking        |
+|         |       permissions                                   |
+|         |                                                     |
 | `domid` | The domain-id to which the permission relates       |
 
 Note that perm1 defines the domain owning the code. See [4] for more
--
generated by git-patchbot for /home/xen/git/xen.git#master