Merge remote-tracking branch 'remotes/awilliam/tags/vfio-fixes-20180823.1' into staging

VFIO fixes 2018-08-23

 - Fix coverity reported issue with use of realpath (Alex Williamson)

 - Cleanup file descriptor in error path (Alex Williamson)

 - Fix postcopy use of new balloon inhibitor (Alex Williamson)

# gpg: Signature made Thu 23 Aug 2018 17:46:41 BST
# gpg:                using RSA key 239B9B6E3BB08B22
# gpg: Good signature from "Alex Williamson <alex.williamson@redhat.com>"
# gpg:                 aka "Alex Williamson <alex@shazbot.org>"
# gpg:                 aka "Alex Williamson <alwillia@redhat.com>"
# gpg:                 aka "Alex Williamson <alex.l.williamson@gmail.com>"
# Primary key fingerprint: 42F6 C04E 540B D1A9 9E7B  8A90 239B 9B6E 3BB0 8B22

* remotes/awilliam/tags/vfio-fixes-20180823.1:
  postcopy: Synchronize usage of the balloon inhibitor
  vfio/pci: Fix failure to close file descriptor on error
  vfio/pci: Handle subsystem realpath() returning NULL
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/vfio/common.c

@@ -1432,6 +1432,7 @@ int vfio_get_device(VFIOGroup *group, const char *name,
         if (!QLIST_EMPTY(&group->device_list)) {
             error_setg(errp,
                        "Inconsistent device balloon setting within group");
+            close(fd);
             return -1;
         }
 

hw/vfio/pci.c

@@ -2879,7 +2879,7 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
     tmp = g_strdup_printf("%s/subsystem", vdev->vbasedev.sysfsdev);
     subsys = realpath(tmp, NULL);
     g_free(tmp);
-    is_mdev = (strcmp(subsys, "/sys/bus/mdev") == 0);
+    is_mdev = subsys && (strcmp(subsys, "/sys/bus/mdev") == 0);
     free(subsys);
 
     trace_vfio_mdev(vdev->vbasedev.name, is_mdev);

migration/postcopy-ram.c

@@ -509,6 +509,20 @@ int postcopy_ram_incoming_init(MigrationIncomingState *mis)
     return 0;
 }
 
+/*
+ * Manage a single vote to the QEMU balloon inhibitor for all postcopy usage,
+ * last caller wins.
+ */
+static void postcopy_balloon_inhibit(bool state)
+{
+    static bool cur_state = false;
+
+    if (state != cur_state) {
+        qemu_balloon_inhibit(state);
+        cur_state = state;
+    }
+}
+
 /*
  * At the end of a migration where postcopy_ram_incoming_init was called.
  */
@@ -539,7 +553,7 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
         mis->have_fault_thread = false;
     }
 
-    qemu_balloon_inhibit(false);
+    postcopy_balloon_inhibit(false);
 
     if (enable_mlock) {
         if (os_mlock() < 0) {
@@ -1109,7 +1123,7 @@ int postcopy_ram_enable_notify(MigrationIncomingState *mis)
      * Ballooning can mark pages as absent while we're postcopying
      * that would cause false userfaults.
      */
-    qemu_balloon_inhibit(true);
+    postcopy_balloon_inhibit(true);
 
     trace_postcopy_ram_enable_notify();