ivshmem: Fix unplug of device "ivshmem-plain"

Commit 2aece63c8a "hostmem: detect host backend memory is being used
properly" fixed "ivshmem-plain" to reject memory backends that are
already in use, and to block their deletion while in use.  Two bugs
escaped review:

* New ivshmem_plain_exit() fails to call ivshmem_exit().  This breaks
  unplug.  Reproducer: migration after unplug still fails with
  "Migration is disabled when using feature 'peer mode' in device
  'ivshmem'".

* It failed to update legacy "ivshmem".  Harmless, because it creates
  the memory backend itself, and nothing else should use it.

Fix by moving the two host_memory_backend_set_mapped() calls into
ivshmem_common_realize() and ivshmem_exit(), guarded by s->hostmem.

Fixes: 2aece63c8a9d2c3a8ff41d2febc4cdeff2633331
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20180926163709.22876-1-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 5 insertions, 9 deletions

diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
index 6febbabcaa..8cb17b9dd4 100644
--- a/hw/misc/ivshmem.c
+++ b/hw/misc/ivshmem.c
@@ -911,6 +911,7 @@ static void ivshmem_common_realize(PCIDevice *dev, Error **errp)
         IVSHMEM_DPRINTF("using hostmem\n");
 
         s->ivshmem_bar2 = host_memory_backend_get_memory(s->hostmem);
+        host_memory_backend_set_mapped(s->hostmem, true);
     } else {
         Chardev *chr = qemu_chr_fe_get_driver(&s->server_chr);
         assert(chr);
@@ -993,6 +994,10 @@ static void ivshmem_exit(PCIDevice *dev)
         vmstate_unregister_ram(s->ivshmem_bar2, DEVICE(dev));
     }
 
+    if (s->hostmem) {
+        host_memory_backend_set_mapped(s->hostmem, false);
+    }
+
     if (s->peers) {
         for (i = 0; i < s->nb_peers; i++) {
             close_peer_eventfds(s, i);
@@ -1101,14 +1106,6 @@ static void ivshmem_plain_realize(PCIDevice *dev, Error **errp)
     }
 
     ivshmem_common_realize(dev, errp);
-    host_memory_backend_set_mapped(s->hostmem, true);
-}
-
-static void ivshmem_plain_exit(PCIDevice *pci_dev)
-{
-    IVShmemState *s = IVSHMEM_COMMON(pci_dev);
-
-    host_memory_backend_set_mapped(s->hostmem, false);
 }
 
 static void ivshmem_plain_class_init(ObjectClass *klass, void *data)
@@ -1117,7 +1114,6 @@ static void ivshmem_plain_class_init(ObjectClass *klass, void *data)
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
 
     k->realize = ivshmem_plain_realize;
-    k->exit = ivshmem_plain_exit;
     dc->props = ivshmem_plain_properties;
     dc->vmsd = &ivshmem_plain_vmsd;
 }