vfio: Make migration support experimental

Support for migration of vfio devices is still in flux.  Developers
are attempting to add support for new devices and new architectures,
but none are yet readily available for validation.  We have concerns
whether we're transferring device resources at the right point in the
migration, whether we're guaranteeing that updates during pre-copy are
migrated, and whether we can provide bit-stream compatibility should
any of this change.  Even the question of whether devices should
participate in dirty page tracking during pre-copy seems contentious.
In short, migration support has not had enough soak time and it feels
premature to mark it as supported.

Create an experimental option such that we can continue to develop.

[Retaining previous acks/reviews for a previously identical code
 change with different specifics in the commit log.]

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index 5526156..00daa50 100644 (file)
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -882,7 +882,7 @@ int vfio_migration_probe(VFIODevice *vbasedev, Error **errp)
     Error *local_err = NULL;
     int ret = -ENOTSUP;
 
-    if (!container->dirty_pages_supported) {
+    if (!vbasedev->enable_migration || !container->dirty_pages_supported) {
         goto add_blocker;
     }
 

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 58c0ce8..1349b90 100644 (file)
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -3194,6 +3194,8 @@ 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_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/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index baeb4dc..2119872 100644 (file)
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -123,6 +123,7 @@ typedef struct VFIODevice {
     bool needs_reset;
     bool no_mmap;
     bool ram_block_discard_allowed;
+    bool enable_migration;
     VFIODeviceOps *ops;
     unsigned int num_irqs;
     unsigned int num_regions;