[RFC PATCH v2 1/3] vfio: Move the saving of the config space to the right place in VFIO migration

[Shenming Lu <lushenming@huawei.com>]

On ARM64 the VFIO SET_IRQS ioctl is dependent on the VM interrupt
setup, if the restoring of the VFIO PCI device config space is
before the VGIC, an error might occur in the kernel.

So we move the saving of the config space to the non-iterable
process, so that it will be called after the VGIC according to
their priorities.

As for the possible dependence of the device specific migration
data on it's config space, we can let the vendor driver to
include any config info it needs in its own data stream.
(Should we note this in the header file linux-headers/linux/vfio.h?)

Signed-off-by: Shenming Lu <lushenming@huawei.com>
---
 hw/vfio/migration.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index 00daa50ed8..3b9de1353a 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -575,11 +575,6 @@ static int vfio_save_complete_precopy(QEMUFile *f, void *opaque)
         return ret;
     }
 
-    ret = vfio_save_device_config_state(f, opaque);
-    if (ret) {
-        return ret;
-    }
-
     ret = vfio_update_pending(vbasedev);
     if (ret) {
         return ret;
@@ -620,6 +615,19 @@ static int vfio_save_complete_precopy(QEMUFile *f, void *opaque)
     return ret;
 }
 
+static void vfio_save_state(QEMUFile *f, void *opaque)
+{
+    VFIODevice *vbasedev = opaque;
+    int ret;
+
+    /* The device specific data is migrated in the iterable process. */
+    ret = vfio_save_device_config_state(f, opaque);
+    if (ret) {
+        error_report("%s: Failed to save device config space",
+                     vbasedev->name);
+    }
+}
+
 static int vfio_load_setup(QEMUFile *f, void *opaque)
 {
     VFIODevice *vbasedev = opaque;
@@ -670,11 +678,7 @@ static int vfio_load_state(QEMUFile *f, void *opaque, int version_id)
         switch (data) {
         case VFIO_MIG_FLAG_DEV_CONFIG_STATE:
         {
-            ret = vfio_load_device_config_state(f, opaque);
-            if (ret) {
-                return ret;
-            }
-            break;
+            return vfio_load_device_config_state(f, opaque);
         }
         case VFIO_MIG_FLAG_DEV_SETUP_STATE:
         {
@@ -720,6 +724,7 @@ static SaveVMHandlers savevm_vfio_handlers = {
     .save_live_pending = vfio_save_pending,
     .save_live_iterate = vfio_save_iterate,
     .save_live_complete_precopy = vfio_save_complete_precopy,
+    .save_state = vfio_save_state,
     .load_setup = vfio_load_setup,
     .load_cleanup = vfio_load_cleanup,
     .load_state = vfio_load_state,
-- 
2.19.1