When there are multiple memory backends in use, including the object type
name, ID and the property name in the error message can help users to
locate the error.

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Suggested-by: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
---
 backends/hostmem-file.c |  9 ++++++---
 backends/hostmem.c      | 11 +++++++----
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index 67ecfed895..df06b547a6 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -80,7 +80,8 @@ static void set_mem_path(Object *o, const char *str, Error **errp)
     HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
 
     if (host_memory_backend_mr_inited(backend)) {
-        error_setg(errp, "cannot change property value");
+        error_setg(errp, "cannot change property 'mem-path' of %s '%s'",
+                   object_get_typename(o), backend->id);
         return;
     }
     g_free(fb->mem_path);
@@ -100,7 +101,8 @@ static void file_memory_backend_set_share(Object *o, bool value, Error **errp)
     HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
 
     if (host_memory_backend_mr_inited(backend)) {
-        error_setg(errp, "cannot change property value");
+        error_setg(errp, "cannot change property 'share' of %s '%s'",
+                   object_get_typename(o), backend->id);
         return;
     }
     fb->share = value;
@@ -137,7 +139,8 @@ static void file_memory_backend_set_align(Object *o, Visitor *v,
     uint64_t val;
 
     if (host_memory_backend_mr_inited(backend)) {
-        error_setg(&local_err, "cannot change property value");
+        error_setg(&local_err, "cannot change property '%s' of %s '%s'",
+                   name, object_get_typename(o), backend->id);
         goto out;
     }
 
diff --git a/backends/hostmem.c b/backends/hostmem.c
index ee2c2d5bfd..6853d19bc5 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -46,7 +46,8 @@ host_memory_backend_set_size(Object *obj, Visitor *v, const char *name,
     uint64_t value;
 
     if (host_memory_backend_mr_inited(backend)) {
-        error_setg(&local_err, "cannot change property value");
+        error_setg(&local_err, "cannot change property %s of %s '%s'",
+                   name, object_get_typename(obj), backend->id);
         goto out;
     }
 
@@ -55,8 +56,9 @@ host_memory_backend_set_size(Object *obj, Visitor *v, const char *name,
         goto out;
     }
     if (!value) {
-        error_setg(&local_err, "Property '%s.%s' doesn't take value '%"
-                   PRIu64 "'", object_get_typename(obj), name, value);
+        error_setg(&local_err,
+                   "property '%s' of %s '%s' doesn't take value '%" PRIu64 "'",
+                   name, object_get_typename(obj), backend->id, value);
         goto out;
     }
     backend->size = value;
@@ -363,7 +365,8 @@ static void set_id(Object *o, const char *str, Error **errp)
     HostMemoryBackend *backend = MEMORY_BACKEND(o);
 
     if (backend->id) {
-        error_setg(errp, "cannot change property value");
+        error_setg(errp, "cannot change property 'id' of %s '%s'",
+                   object_get_typename(o), backend->id);
         return;
     }
     backend->id = g_strdup(str);
-- 
2.14.1