vfio/migration: Make VFIO migration non-experimental

The major parts of VFIO migration are supported today in QEMU. This
includes basic VFIO migration, device dirty page tracking and precopy
support.

Thus, at this point in time, it seems appropriate to make VFIO migration
non-experimental: remove the x prefix from enable_migration property,
change it to ON_OFF_AUTO and let the default value be AUTO.

In addition, make the following adjustments:
1. When enable_migration is ON and migration is not supported, fail VFIO
   device realization.
2. When enable_migration is AUTO (i.e., not explicitly enabled), require
   device dirty tracking support. This is because device dirty tracking
   is currently the only method to do dirty page tracking, which is
   essential for migrating in a reasonable downtime. Setting
   enable_migration to ON will not require device dirty tracking.
3. Make migration error and blocker messages more elaborate.
4. Remove error prints in vfio_migration_query_flags().
5. Rename trace_vfio_migration_probe() to
   trace_vfio_migration_realize().

Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>

4 files changed, 70 insertions, 31 deletions

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 28ec9e9..77e2ee0 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -381,7 +381,7 @@ static unsigned int vfio_migratable_device_num(void)
     return device_num;
 }
 
-int vfio_block_multiple_devices_migration(Error **errp)
+int vfio_block_multiple_devices_migration(VFIODevice *vbasedev, Error **errp)
 {
     int ret;
 
@@ -390,6 +390,12 @@ int vfio_block_multiple_devices_migration(Error **errp)
         return 0;
     }
 
+    if (vbasedev->enable_migration == ON_OFF_AUTO_ON) {
+        error_setg(errp, "Migration is currently not supported with multiple "
+                         "VFIO devices");
+        return -EINVAL;
+    }
+
     error_setg(&multiple_devices_migration_blocker,
                "Migration is currently not supported with multiple "
                "VFIO devices");
@@ -427,7 +433,7 @@ static bool vfio_viommu_preset(void)
     return false;
 }
 
-int vfio_block_giommu_migration(Error **errp)
+int vfio_block_giommu_migration(VFIODevice *vbasedev, Error **errp)
 {
     int ret;
 
@@ -436,6 +442,12 @@ int vfio_block_giommu_migration(Error **errp)
         return 0;
     }
 
+    if (vbasedev->enable_migration == ON_OFF_AUTO_ON) {
+        error_setg(errp,
+                   "Migration is currently not supported with vIOMMU enabled");
+        return -EINVAL;
+    }
+
     error_setg(&giommu_migration_blocker,
                "Migration is currently not supported with vIOMMU enabled");
     ret = migrate_add_blocker(giommu_migration_blocker, errp);
diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index 7cf1439..1db7d52 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -724,14 +724,6 @@ static int vfio_migration_query_flags(VFIODevice *vbasedev, uint64_t *mig_flags)
     feature->argsz = sizeof(buf);
     feature->flags = VFIO_DEVICE_FEATURE_GET | VFIO_DEVICE_FEATURE_MIGRATION;
     if (ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature)) {
-        if (errno == ENOTTY) {
-            error_report("%s: VFIO migration is not supported in kernel",
-                         vbasedev->name);
-        } else {
-            error_report("%s: Failed to query VFIO migration support, err: %s",
-                         vbasedev->name, strerror(errno));
-        }
-
         return -errno;
     }
 
@@ -810,6 +802,27 @@ static int vfio_migration_init(VFIODevice *vbasedev)
     return 0;
 }
 
+static int vfio_block_migration(VFIODevice *vbasedev, Error *err, Error **errp)
+{
+    int ret;
+
+    if (vbasedev->enable_migration == ON_OFF_AUTO_ON) {
+        error_propagate(errp, err);
+        return -EINVAL;
+    }
+
+    vbasedev->migration_blocker = error_copy(err);
+    error_free(err);
+
+    ret = migrate_add_blocker(vbasedev->migration_blocker, errp);
+    if (ret < 0) {
+        error_free(vbasedev->migration_blocker);
+        vbasedev->migration_blocker = NULL;
+    }
+
+    return ret;
+}
+
 /* ---------------------------------------------------------------------- */
 
 int64_t vfio_mig_bytes_transferred(void)
@@ -824,40 +837,54 @@ void vfio_reset_bytes_transferred(void)
 
 int vfio_migration_realize(VFIODevice *vbasedev, Error **errp)
 {
-    int ret = -ENOTSUP;
+    Error *err = NULL;
+    int ret;
 
-    if (!vbasedev->enable_migration) {
-        goto add_blocker;
+    if (vbasedev->enable_migration == ON_OFF_AUTO_OFF) {
+        error_setg(&err, "%s: Migration is disabled for VFIO device",
+                   vbasedev->name);
+        return vfio_block_migration(vbasedev, err, errp);
     }
 
     ret = vfio_migration_init(vbasedev);
     if (ret) {
-        goto add_blocker;
+        if (ret == -ENOTTY) {
+            error_setg(&err, "%s: VFIO migration is not supported in kernel",
+                       vbasedev->name);
+        } else {
+            error_setg(&err,
+                       "%s: Migration couldn't be initialized for VFIO device, "
+                       "err: %d (%s)",
+                       vbasedev->name, ret, strerror(-ret));
+        }
+
+        return vfio_block_migration(vbasedev, err, errp);
+    }
+
+    if (!vbasedev->dirty_pages_supported) {
+        if (vbasedev->enable_migration == ON_OFF_AUTO_AUTO) {
+            error_setg(&err,
+                       "%s: VFIO device doesn't support device dirty tracking",
+                       vbasedev->name);
+            return vfio_block_migration(vbasedev, err, errp);
+        }
+
+        warn_report("%s: VFIO device doesn't support device dirty tracking",
+                    vbasedev->name);
     }
 
-    ret = vfio_block_multiple_devices_migration(errp);
+    ret = vfio_block_multiple_devices_migration(vbasedev, errp);
     if (ret) {
         return ret;
     }
 
-    ret = vfio_block_giommu_migration(errp);
+    ret = vfio_block_giommu_migration(vbasedev, errp);
     if (ret) {
         return ret;
     }
 
-    trace_vfio_migration_probe(vbasedev->name);
+    trace_vfio_migration_realize(vbasedev->name);
     return 0;
-
-add_blocker:
-    error_setg(&vbasedev->migration_blocker,
-               "VFIO device doesn't support migration");
-
-    ret = migrate_add_blocker(vbasedev->migration_blocker, errp);
-    if (ret < 0) {
-        error_free(vbasedev->migration_blocker);
-        vbasedev->migration_blocker = NULL;
-    }
-    return ret;
 }
 
 void vfio_migration_exit(VFIODevice *vbasedev)
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 8fb2c53..73e19a0 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -3347,8 +3347,8 @@ static Property vfio_pci_dev_properties[] = {
                     VFIO_FEATURE_ENABLE_REQ_BIT, true),
     DEFINE_PROP_BIT("x-igd-opregion", VFIOPCIDevice, features,
                     VFIO_FEATURE_ENABLE_IGD_OPREGION_BIT, false),
-    DEFINE_PROP_BOOL("x-enable-migration", VFIOPCIDevice,
-                     vbasedev.enable_migration, false),
+    DEFINE_PROP_ON_OFF_AUTO("enable-migration", VFIOPCIDevice,
+                            vbasedev.enable_migration, ON_OFF_AUTO_AUTO),
     DEFINE_PROP_BOOL("x-no-mmap", VFIOPCIDevice, vbasedev.no_mmap, false),
     DEFINE_PROP_BOOL("x-balloon-allowed", VFIOPCIDevice,
                      vbasedev.ram_block_discard_allowed, false),
diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
index e328d64..ee7509e 100644
--- a/hw/vfio/trace-events
+++ b/hw/vfio/trace-events
@@ -155,7 +155,7 @@ vfio_load_cleanup(const char *name) " (%s)"
 vfio_load_device_config_state(const char *name) " (%s)"
 vfio_load_state(const char *name, uint64_t data) " (%s) data 0x%"PRIx64
 vfio_load_state_device_data(const char *name, uint64_t data_size, int ret) " (%s) size 0x%"PRIx64" ret %d"
-vfio_migration_probe(const char *name) " (%s)"
+vfio_migration_realize(const char *name) " (%s)"
 vfio_migration_set_state(const char *name, const char *state) " (%s) state %s"
 vfio_migration_state_notifier(const char *name, const char *state) " (%s) state %s"
 vfio_save_block(const char *name, int data_size) " (%s) data_size %d"