commit 4a66c7a9996bb1bb1191170b172daa54e226d7ff
author Ilya Maximets <i.maximets@samsung.com> Mon Mar 11 16:58:47 2019 +0300
committer Eduardo Habkost <ehabkost@redhat.com> Mon Mar 11 17:16:56 2019 -0300
tree ffc86e58bff453e6cd3bc64621426c7baf7580a5
parent f6a0d06ba72a0c493e1e05872caf2f3781af316d

hostmem-memfd: disable for systems without sealing support

If seals are not supported, memfd_create() will fail.
Furthermore, there is no way to disable it in this case because
'.seal' property is not registered.

This issue leads to vhost-user-test failures on RHEL 7.2:

  qemu-system-x86_64: -object memory-backend-memfd,id=mem,size=2M,: \
                      failed to create memfd: Invalid argument

and actually breaks the feature on such systems.

Let's restrict memfd backend to systems with sealing support.

Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
Message-Id: <20190311135850.6537-2-i.maximets@samsung.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

backends/hostmem-memfd.c

diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c
index 98c9bf3..46b15b9 100644
--- a/backends/hostmem-memfd.c
+++ b/backends/hostmem-memfd.c
@@ -154,15 +154,13 @@
                                               "Huge pages size (ex: 2M, 1G)",
                                               &error_abort);
     }
-    if (qemu_memfd_check(MFD_ALLOW_SEALING)) {
-        object_class_property_add_bool(oc, "seal",
-                                       memfd_backend_get_seal,
-                                       memfd_backend_set_seal,
-                                       &error_abort);
-        object_class_property_set_description(oc, "seal",
-                                              "Seal growing & shrinking",
-                                              &error_abort);
-    }
+    object_class_property_add_bool(oc, "seal",
+                                   memfd_backend_get_seal,
+                                   memfd_backend_set_seal,
+                                   &error_abort);
+    object_class_property_set_description(oc, "seal",
+                                          "Seal growing & shrinking",
+                                          &error_abort);
 }
 
 static const TypeInfo memfd_backend_info = {
@@ -175,7 +173,7 @@
 
 static void register_types(void)
 {
-    if (qemu_memfd_check(0)) {
+    if (qemu_memfd_check(MFD_ALLOW_SEALING)) {
         type_register_static(&memfd_backend_info);
     }
 }