virtio-pci: fix bus master work around on load

Commit c81131db
detects old guests by comparing virtio and
PCI status. It attempts to do this on load,
as well, but load_config callback in a binding
is invoked too early and so the virtio status
isn't set yet.

We could add yet another callback to the
binding, to invoke after load, but it
seems easier to reuse the existing vmstate
callback.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Alexander Graf <agraf@suse.de>
(cherry picked from commit 89c473fd)

hw/virtio-pci.c

@@ -160,13 +160,6 @@ static int virtio_pci_load_config(void * opaque, QEMUFile *f)
     if (proxy->vdev->config_vector != VIRTIO_NO_VECTOR) {
         return msix_vector_use(&proxy->pci_dev, proxy->vdev->config_vector);
     }
-
-    /* Try to find out if the guest has bus master disabled, but is
-       in ready state. Then we have a buggy guest OS. */
-    if ((proxy->vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
-        !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
-        proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
-    }
     return 0;
 }
 
@@ -651,6 +644,12 @@ static void virtio_pci_vmstate_change(void *opaque, bool running)
     VirtIOPCIProxy *proxy = opaque;
 
     if (running) {
+        /* Try to find out if the guest has bus master disabled, but is
+           in ready state. Then we have a buggy guest OS. */
+        if ((proxy->vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
+            !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
+            proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
+        }
         virtio_pci_start_ioeventfd(proxy);
     } else {
         virtio_pci_stop_ioeventfd(proxy);

hw/virtio.h

@@ -92,6 +92,7 @@ typedef struct {
     void (*save_queue)(void * opaque, int n, QEMUFile *f);
     int (*load_config)(void * opaque, QEMUFile *f);
     int (*load_queue)(void * opaque, int n, QEMUFile *f);
+    int (*load_done)(void * opaque, QEMUFile *f);
     unsigned (*get_features)(void * opaque);
     bool (*query_guest_notifiers)(void * opaque);
     int (*set_guest_notifiers)(void * opaque, bool assigned);