[v3] docs: specify numerical values of Xenstore commands

Commit Message

Juergen Gross March 12, 2025, 8:41 a.m. UTC

In docs/misc/xenstore.txt all Xenstore commands are specified, but
the specifications lack the numerical values of the commands.

Add a table with all commands, their values, and a potential remark
(e.g. whether the command is optional).

Reported-by: Jan Beulich <[e-mail]>
Signed-off-by: Juergen Gross <[e-mail]>
---
V2:
- replace "ŕ" with plain "r" (Jan Beulich)
- replace hard tabs with blanks (Jan Beulich)
- allow GET_FEATURES and GET_QUOTA support without SET_* (Jan Beulich)
V3:
- specify error code returned for unsupported commands (Julien Grall)
- reword XS_DIRECTORY_PART related text (Julien Grall)
---
 docs/misc/xenstore.txt | 61 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

Patch

diff --git a/docs/misc/xenstore.txt b/docs/misc/xenstore.txt
index 7e1f031520..72db73deef 100644
--- a/docs/misc/xenstore.txt
+++ b/docs/misc/xenstore.txt
@@ -86,6 +86,67 @@  parts of xenstore inaccessible to some clients.  In any case passing
 bulk data through xenstore is not recommended as the performance
 properties are poor.
 
+---------- Defined Xenstore message types ----------
+
+Below is a table with all defined Xenstore message types (type name
+and its associated numerical value).
+
+Some types are optional to be supported by a specific Xenstore
+implementation.  If an optional type is not supported by a Xenstore
+implementation, Xen tools will continue to work, maybe with slightly
+reduced functionality.  A mandatory type not being supported will
+result in severely reduced functionality, like inability to create
+domains.  In case a type is optional, this is stated in the table with
+the lost functionality in case Xenstore doesn't support that type.
+Any not supported type sent to Xenstore will result in an error response
+with the "ENOSYS" error.
+
+XS_CONTROL               0    optional
+    If not supported, xenstore-control command will not work.
+    XS_DEBUG is a deprecated alias of XS_CONTROL.
+XS_DIRECTORY             1
+XS_READ                  2
+XS_GET_PERMS             3
+XS_WATCH                 4
+XS_UNWATCH               5
+XS_TRANSACTION_START     6
+XS_TRANSACTION_END       7
+XS_INTRODUCE             8
+XS_RELEASE               9
+XS_GET_DOMAIN_PATH      10
+XS_WRITE                11
+XS_MKDIR                12
+XS_RM                   13
+XS_SET_PERMS            14
+XS_WATCH_EVENT          15
+    Not valid in client sent messages.
+    Only valid in Xenstore replies.
+XS_ERROR                16
+    Not valid in client sent messages.
+    Only valid in Xenstore replies.
+XS_IS_DOMAIN_INTRODUCED 17
+XS_RESUME               18
+XS_SET_TARGET           19
+XS_RESTRICT             20    no longer supported
+    XS_RESTRICT has been removed, the type value 20 is invalid.
+XS_RESET_WATCHES        21
+XS_DIRECTORY_PART       22    optional
+    If not supported, the output of xenstore-ls might be incomplete
+    with a node's sub-node list exceeding the maximum payload size
+    (e.g. the "/local/domain" node with more than ca. 1000 domains
+    active).
+XS_GET_FEATURE          23    optional
+XS_SET_FEATURE          24    optional
+    XS_SET_FEATURE requires XS_GET_FEATURE to be supported.
+    If unsupported, setting availability of Xenstore features per
+    domain is not possible.
+XS_GET_QUOTA            25    optional
+XS_SET_QUOTA            26    optional
+    XS_SET_QUOTA requires XS_GET_QUOTA to be supported.
+    If unsupported, setting of Xenstore quota per domain is not
+    possible.
+XS_INVALID           65535
+    Guaranteed invalid type (never supported).
 
 ---------- Xenstore protocol details - introduction ----------