[PATCH v2] Fix fallout from DOMID_ANY ABI breakage

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Commit 23e2479ff9de ("xen/domain: introduce DOMID_ANY") broke at least:

 * xenstored domains
 * The Python bindings
 * The Ocaml bindings (i.e XAPI, and therefore XenServer/XCP-ng)

by causing Xen to reject 0 (the wildcard sentinel since the start of Xen) and
DOMID_INVALID (since 4.21) without adjusting the callers of xc_domain_create().

Under other circumstances I'd revert, but xenstored has gained a dependent use
of DOMID_ANY.

Fix up the remaining in-tree callers of xc_domain_create(), which covers
init-xenstore-domain and the python bindings.

The Ocaml C bindings, like libxc itself, expose this ABI detail to their
caller, but in this case the caller is still internal to the bindings as a
whole.  Adjust the default value in the internal transformation, adding
domid_any for legibility.

Leave a very clear message in CHANGELOG.md that all external callers need
altering.

Fixes: 23e2479ff9de ("xen/domain: introduce DOMID_ANY")
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Anthony PERARD <anthony.perard@xxxxxxxxxx>
CC: Michal Orzel <michal.orzel@xxxxxxx>
CC: Jan Beulich <jbeulich@xxxxxxxx>
CC: Julien Grall <julien@xxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Juergen Gross <jgross@xxxxxxxx>
CC: Denis Mukhin <dmukhin@xxxxxxxx>
CC: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
CC: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
CC: Pau Ruiz Safont <pau.safont@xxxxxxxxxx>
CC: Colin James <colin.barr@xxxxxxxxxx>

v2:
 * Include XEN_DOMCTL_createdomain in CHANGELOG message too
 * Fix the Ocaml stubs too.

There are now 0 Ocaml maintainers.  Pau and Colin reviewed my suggestion on
the Xapi Matrix channel.
---
 CHANGELOG.md                         | 4 ++++
 tools/helpers/init-xenstore-domain.c | 2 +-
 tools/ocaml/libs/xc/xenctrl.ml       | 4 +++-
 tools/python/xen/lowlevel/xc/xc.c    | 2 +-
 4 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 25f5a192ed48..1db3efc4864c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ The format is based on [Keep a 
Changelog](https://keepachangelog.com/en/1.0.0/)
 ## [4.22.0 
UNRELEASED](https://xenbits.xenproject.org/gitweb/?p=xen.git;a=shortlog;h=staging)
 - TBD
 
 ### Changed
+ - Users of XEN_DOMCTL_createdomain/xc_domain_create() must now pass DOMID_ANY
+   to obtain an automatically allocated domid.  The prior sentinel values (0
+   since the start of Xen, and DOMID_INVALID since Xen 4.21) now no longer
+   represent a wildcard input.
  - On x86:
    - Enable pf-fixup option by default for PVH dom0.
 
diff --git a/tools/helpers/init-xenstore-domain.c 
b/tools/helpers/init-xenstore-domain.c
index 01ca667d25d1..2be5831a578d 100644
--- a/tools/helpers/init-xenstore-domain.c
+++ b/tools/helpers/init-xenstore-domain.c
@@ -21,7 +21,7 @@
 
 #define LAPIC_BASE_ADDRESS  0xfee00000UL
 
-static uint32_t domid = ~0;
+static uint32_t domid = DOMID_ANY;
 static char *kernel;
 static char *ramdisk;
 static char *flask;
diff --git a/tools/ocaml/libs/xc/xenctrl.ml b/tools/ocaml/libs/xc/xenctrl.ml
index 97108b9d861a..147afa62c293 100644
--- a/tools/ocaml/libs/xc/xenctrl.ml
+++ b/tools/ocaml/libs/xc/xenctrl.ml
@@ -208,7 +208,9 @@ let with_intf f =
 external domain_create_stub: handle -> domid -> domctl_create_config -> domid
   = "stub_xc_domain_create"
 
-let domain_create handle ?(domid=0) config =
+let domid_any = 0x7ff5 (* DOMID_ANY from public/xen.h *)
+
+let domain_create handle ?(domid=domid_any) config =
   domain_create_stub handle domid config
 
 external domain_sethandle: handle -> domid -> string -> unit
diff --git a/tools/python/xen/lowlevel/xc/xc.c 
b/tools/python/xen/lowlevel/xc/xc.c
index 9feb12ae2b16..a94f01d40b58 100644
--- a/tools/python/xen/lowlevel/xc/xc.c
+++ b/tools/python/xen/lowlevel/xc/xc.c
@@ -118,7 +118,7 @@ static PyObject *pyxc_domain_create(XcObject *self,
                                     PyObject *args,
                                     PyObject *kwds)
 {
-    uint32_t dom = 0, target = 0, max_grant_version = 2;
+    uint32_t dom = DOMID_ANY, target = 0, max_grant_version = 2;
     int      ret;
     size_t   i;
     PyObject *pyhandle = NULL;

base-commit: e63ba93511b33c0d3bb8cc5870f946f41e1d2655
-- 
2.39.5