[v5,31/36] vfio/migration: Add x-migration-multifd-transfer VFIO property

Commit Message

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

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

This property allows configuring at runtime whether to transfer the
particular device state via multifd channels when live migrating that
device.

It defaults to AUTO, which means that VFIO device state transfer via
multifd channels is attempted in configurations that otherwise support it.

Signed-off-by: Maciej S. Szmigiero <[e-mail]>
---
 hw/vfio/migration-multifd.c   | 17 ++++++++++++++++-
 hw/vfio/pci.c                 |  3 +++
 include/hw/vfio/vfio-common.h |  2 ++
 3 files changed, 21 insertions(+), 1 deletion(-)

Patch

diff --git a/hw/vfio/migration-multifd.c b/hw/vfio/migration-multifd.c
index 0cfa9d31732a..18a5ff964a37 100644
--- a/hw/vfio/migration-multifd.c
+++ b/hw/vfio/migration-multifd.c
@@ -460,11 +460,26 @@  bool vfio_multifd_transfer_supported(void)
 
 bool vfio_multifd_transfer_enabled(VFIODevice *vbasedev)
 {
-    return false;
+    VFIOMigration *migration = vbasedev->migration;
+
+    return migration->multifd_transfer;
 }
 
 bool vfio_multifd_transfer_setup(VFIODevice *vbasedev, Error **errp)
 {
+    VFIOMigration *migration = vbasedev->migration;
+
+    /*
+     * Make a copy of this setting at the start in case it is changed
+     * mid-migration.
+     */
+    if (vbasedev->migration_multifd_transfer == ON_OFF_AUTO_AUTO) {
+        migration->multifd_transfer = vfio_multifd_transfer_supported();
+    } else {
+        migration->multifd_transfer =
+            vbasedev->migration_multifd_transfer == ON_OFF_AUTO_ON;
+    }
+
     if (vfio_multifd_transfer_enabled(vbasedev) &&
         !vfio_multifd_transfer_supported()) {
         error_setg(errp,
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 89d900e9cf0c..184ff882f9d1 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -3377,6 +3377,9 @@  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_BOOL("migration-events", VFIOPCIDevice,
                      vbasedev.migration_events, false),
     DEFINE_PROP_BOOL("x-no-mmap", VFIOPCIDevice, vbasedev.no_mmap, false),
diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index ba851917f9fc..3006931accf6 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -91,6 +91,7 @@  typedef struct VFIOMigration {
     uint64_t mig_flags;
     uint64_t precopy_init_size;
     uint64_t precopy_dirty_size;
+    bool multifd_transfer;
     VFIOMultifd *multifd;
     bool initial_data_sent;
 
@@ -153,6 +154,7 @@  typedef struct VFIODevice {
     bool no_mmap;
     bool ram_block_discard_allowed;
     OnOffAuto enable_migration;
+    OnOffAuto migration_multifd_transfer;
     bool migration_events;
     VFIODeviceOps *ops;
     unsigned int num_irqs;