[PATCH v5 8/9] vfio/migration: Add x-allow-pre-copy VFIO device property

[Avihai Horon]

Add a new VFIO device property x-allow-pre-copy to keep migration
compatibility to/from older QEMU versions that don't have VFIO pre-copy
support.

Signed-off-by: Avihai Horon <avih...@nvidia.com>
Reviewed-by: Cédric Le Goater <c...@redhat.com>
---
 include/hw/vfio/vfio-common.h | 1 +
 hw/core/machine.c             | 1 +
 hw/vfio/migration.c           | 3 ++-
 hw/vfio/pci.c                 | 2 ++
 4 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index 1db901c194..a53ecbe2e0 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -146,6 +146,7 @@ typedef struct VFIODevice {
     VFIOMigration *migration;
     Error *migration_blocker;
     OnOffAuto pre_copy_dirty_page_tracking;
+    bool allow_pre_copy;
     bool dirty_pages_supported;
     bool dirty_tracking;
 } VFIODevice;
diff --git a/hw/core/machine.c b/hw/core/machine.c
index 1000406211..64ac3fe38e 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -41,6 +41,7 @@
 
 GlobalProperty hw_compat_8_0[] = {
     { "migration", "multifd-flush-after-each-section", "on"},
+    { "vfio-pci", "x-allow-pre-copy", "false" },
 };
 const size_t hw_compat_8_0_len = G_N_ELEMENTS(hw_compat_8_0);
 
diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index d8f6a22ae1..cb6923ed3f 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -323,7 +323,8 @@ static bool vfio_precopy_supported(VFIODevice *vbasedev)
 {
     VFIOMigration *migration = vbasedev->migration;
 
-    return migration->mig_flags & VFIO_MIGRATION_PRE_COPY;
+    return vbasedev->allow_pre_copy &&
+           migration->mig_flags & VFIO_MIGRATION_PRE_COPY;
 }
 
 /* ---------------------------------------------------------------------- */
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 73874a94de..c69813af7f 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -3335,6 +3335,8 @@ static Property vfio_pci_dev_properties[] = {
     DEFINE_PROP_ON_OFF_AUTO("x-pre-copy-dirty-page-tracking", VFIOPCIDevice,
                             vbasedev.pre_copy_dirty_page_tracking,
                             ON_OFF_AUTO_ON),
+    DEFINE_PROP_BOOL("x-allow-pre-copy", VFIOPCIDevice,
+                     vbasedev.allow_pre_copy, true),
     DEFINE_PROP_ON_OFF_AUTO("display", VFIOPCIDevice,
                             display, ON_OFF_AUTO_OFF),
     DEFINE_PROP_UINT32("xres", VFIOPCIDevice, display_xres, 0),
-- 
2.26.3