[Xen-devel] [PATCH v2] libxl: fix assertion failure in stub domain creation

[Paul Durrant <pdurrant@amazon.com>]

An assertion in libxl__domain_make():

'soft_reset || *domid == INVALID_DOMID'

does not hold true for stub domain creation, where soft_reset is false
but the passed in domid == 0. This is easily fixed by changing the
initializer in libxl__spawn_stub_dm().

NOTE: The comment for XEN_DOMCTL_createdomain in domctl.h is changed to
      reflect reality.

Fixes: 75259239d85d ("libxl_create: make 'soft reset' explicit")
Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Wei Liu <wl@xen.org>
Cc: Anthony PERARD <anthony.perard@citrix.com>
Cc: Roger Pau Monné <roger.pau@citrix.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Julien Grall <julien@xen.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>

An example of the assertion failure can be seen at:

http://logs.test-lab.xenproject.org/osstest/logs/146726/test-amd64-amd64-xl-qemut-stubdom-debianhvm-amd64-xsm/10.ts-debian-hvm-install.log
---
 tools/libxl/libxl_dm.c      | 2 +-
 xen/include/public/domctl.h | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index f758daf3b6..3b1da90167 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -2127,7 +2127,7 @@ void libxl__spawn_stub_dm(libxl__egc *egc, libxl__stub_dm_spawn_state *sdss)
         goto out;
     }
 
-    sdss->pvqemu.guest_domid = 0;
+    sdss->pvqemu.guest_domid = INVALID_DOMID;
 
     libxl_domain_create_info_init(&dm_config->c_info);
     dm_config->c_info.type = LIBXL_DOMAIN_TYPE_PV;
diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 2bb7397923..fec6f6fdd1 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -42,7 +42,8 @@
 
 /*
  * NB. xen_domctl.domain is an IN/OUT parameter for this operation.
- * If it is specified as zero, an id is auto-allocated and returned.
+ * If it is specified as an invalid value (0 or >= DOMID_FIRST_RESERVED),
+ * an id is auto-allocated and returned.
  */
 /* XEN_DOMCTL_createdomain */
 struct xen_domctl_createdomain {
-- 
2.20.1


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