[v5,32/36] vfio/migration: Make x-migration-multifd-transfer VFIO property mutable

Commit Message

Maciej S. Szmigiero Feb. 19, 2025, 8:34 p.m. UTC

From: "Maciej S. Szmigiero" <[e-mail]>

DEFINE_PROP_ON_OFF_AUTO() property isn't runtime-mutable so using it
would mean that the source VM would need to decide upfront at startup
time whether it wants to do a multifd device state transfer at some
point.

Source VM can run for a long time before being migrated so it is
desirable to have a fallback mechanism to the old way of transferring
VFIO device state if it turns to be necessary.

This brings this property to the same mutability level as ordinary
migration parameters, which too can be adjusted at the run time.

Signed-off-by: Maciej S. Szmigiero <[e-mail]>
---
 hw/vfio/pci.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

Patch

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 184ff882f9d1..9111805ae06c 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -3353,6 +3353,8 @@  static void vfio_instance_init(Object *obj)
     pci_dev->cap_present |= QEMU_PCI_CAP_EXPRESS;
 }
 
+static PropertyInfo qdev_prop_on_off_auto_mutable;
+
 static const Property vfio_pci_dev_properties[] = {
     DEFINE_PROP_PCI_HOST_DEVADDR("host", VFIOPCIDevice, host),
     DEFINE_PROP_UUID_NODEFAULT("vf-token", VFIOPCIDevice, vf_token),
@@ -3377,9 +3379,10 @@  static const Property vfio_pci_dev_properties[] = {
                     VFIO_FEATURE_ENABLE_IGD_OPREGION_BIT, false),
     DEFINE_PROP_ON_OFF_AUTO("enable-migration", VFIOPCIDevice,
                             vbasedev.enable_migration, ON_OFF_AUTO_AUTO),
-    DEFINE_PROP_ON_OFF_AUTO("x-migration-multifd-transfer", VFIOPCIDevice,
-                            vbasedev.migration_multifd_transfer,
-                            ON_OFF_AUTO_AUTO),
+    DEFINE_PROP("x-migration-multifd-transfer", VFIOPCIDevice,
+                vbasedev.migration_multifd_transfer,
+                qdev_prop_on_off_auto_mutable, OnOffAuto,
+                .set_default = true, .defval.i = ON_OFF_AUTO_AUTO),
     DEFINE_PROP_BOOL("migration-events", VFIOPCIDevice,
                      vbasedev.migration_events, false),
     DEFINE_PROP_BOOL("x-no-mmap", VFIOPCIDevice, vbasedev.no_mmap, false),
@@ -3475,6 +3478,9 @@  static const TypeInfo vfio_pci_nohotplug_dev_info = {
 
 static void register_vfio_pci_dev_type(void)
 {
+    qdev_prop_on_off_auto_mutable = qdev_prop_on_off_auto;
+    qdev_prop_on_off_auto_mutable.realized_set_allowed = true;
+
     type_register_static(&vfio_pci_dev_info);
     type_register_static(&vfio_pci_nohotplug_dev_info);
 }