[PATCH v4 4/5] vfio/pci: Free resources when vfio_migration_realize fails

[Zhenzhong Duan <zhenzhong.duan@intel.com>]

When vfio_realize() succeeds, hot unplug will call vfio_exitfn()
to free resources allocated in vfio_realize(); when vfio_realize()
fails, vfio_exitfn() is never called and we need to free resources
in vfio_realize().

In the case that vfio_migration_realize() fails,
e.g: with -only-migratable & enable-migration=off, we see below:

(qemu) device_add vfio-pci,host=81:11.1,id=vfio1,bus=root1,enable-migration=off
0000:81:11.1: Migration disabled
Error: disallowing migration blocker (--only-migratable) for: 0000:81:11.1: Migration is disabled for VFIO device

If we hotplug again we should see same log as above, but we see:
(qemu) device_add vfio-pci,host=81:11.1,id=vfio1,bus=root1,enable-migration=off
Error: vfio 0000:81:11.1: device is already attached

That's because some references to VFIO device isn't released,
we should check return value of vfio_migration_realize() and
release the references, then VFIO device will be truely
released when hotplug fails.

Fixes: a22651053b59 ("vfio: Make vfio-pci device migration capable")
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
---
 hw/vfio/pci.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 54a8179d1c64..dc69d3031b24 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -3210,6 +3210,7 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
         ret = vfio_migration_realize(vbasedev, errp);
         if (ret) {
             error_report("%s: Migration disabled", vbasedev->name);
+            goto out_vfio_migration;
         }
     }
 
@@ -3219,6 +3220,8 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
 
     return;
 
+out_vfio_migration:
+    vfio_migration_exit(vbasedev);
 out_deregister:
     vfio_disable_interrupts(vdev);
 out_intx_disable:
-- 
2.34.1