[PATCH RFCv2 7/8] vfio/migration: Don't block migration device dirty tracking is unsupported

[Joao Martins]

By default VFIO migration is set to auto, which will support live
migration if the migration capability is set *and* also dirty page
tracking is supported.

For testing purposes one can force enable without dirty page tracking
via enable-migration=on, but that option is generally left for testing
purposes.

So starting with IOMMU dirty tracking it can use to acomodate the lack of
VF dirty page tracking allowing us to minimize the VF requirements for
migration and thus enabling migration by default for those.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
 hw/vfio/iommufd.c        | 3 +--
 hw/vfio/migration.c      | 4 +++-
 include/sysemu/iommufd.h | 1 +
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/hw/vfio/iommufd.c b/hw/vfio/iommufd.c
index 697d40841d7f..78d8f4391b68 100644
--- a/hw/vfio/iommufd.c
+++ b/hw/vfio/iommufd.c
@@ -275,8 +275,7 @@ static int iommufd_cdev_detach_ioas_hwpt(VFIODevice 
*vbasedev, Error **errp)
     return ret;
 }
 
-static bool iommufd_dirty_pages_supported(IOMMUFDDevice *iommufd_dev,
-                                          Error **errp)
+bool iommufd_dirty_pages_supported(IOMMUFDDevice *iommufd_dev, Error **errp)
 {
     uint64_t caps;
     int r;
diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index 70e6b1a709f9..674e76b3f3df 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -938,7 +938,9 @@ bool vfio_migration_realize(VFIODevice *vbasedev, Error 
**errp)
         return !vfio_block_migration(vbasedev, err, errp);
     }
 
-    if (!vbasedev->dirty_pages_supported) {
+    if (!vbasedev->dirty_pages_supported &&
+        (vbasedev->iommufd_dev.iommufd &&
+         !iommufd_dirty_pages_supported(&vbasedev->iommufd_dev, &err))) {
         if (vbasedev->enable_migration == ON_OFF_AUTO_AUTO) {
             error_setg(&err,
                        "%s: VFIO device doesn't support device dirty tracking",
diff --git a/include/sysemu/iommufd.h b/include/sysemu/iommufd.h
index bc6607e3d444..d6be49f2ac78 100644
--- a/include/sysemu/iommufd.h
+++ b/include/sysemu/iommufd.h
@@ -53,6 +53,7 @@ typedef struct IOMMUFDDevice {
 void iommufd_device_init(IOMMUFDDevice *idev);
 int iommufd_device_get_hw_capabilities(IOMMUFDDevice *idev, uint64_t *caps,
                                        Error **errp);
+bool iommufd_dirty_pages_supported(IOMMUFDDevice *idev, Error **errp);
 int iommufd_backend_alloc_hwpt(int iommufd, uint32_t dev_id,
                                uint32_t pt_id, uint32_t flags,
                                uint32_t data_type, uint32_t data_len,
-- 
2.39.3