From: Marc-André Lureau <marcandre.lureau@redhat.com>

Commit dfcf74fa ("virtio-gpu: fix scanout migration post-load") broke
forward/backward version migration. Versioning of nested VMSD structures
is not straightforward, as the wire format doesn't have nested
structures versions. Introduce x-scanout-vmstate-version and a field
test to save/load appropriately according to the machine version.

Fixes: dfcf74fa ("virtio-gpu: fix scanout migration post-load")
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Fiona Ebner <f.ebner@proxmox.com>
Tested-by: Fiona Ebner <f.ebner@proxmox.com>
[fixed long lines]
Signed-off-by: Fabiano Rosas <farosas@suse.de>
(cherry picked from commit 40a23ef643664b5c1021a9789f9d680b6294fb50)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 3a5a8d473d..4273de16a0 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -37,6 +37,7 @@ GlobalProperty hw_compat_8_2[] = {
     { "migration", "zero-page-detection", "legacy"},
     { TYPE_VIRTIO_IOMMU_PCI, "granule", "4k" },
     { TYPE_VIRTIO_IOMMU_PCI, "aw-bits", "64" },
+    { "virtio-gpu-device", "x-scanout-vmstate-version", "1" },
 };
 const size_t hw_compat_8_2_len = G_N_ELEMENTS(hw_compat_8_2);
 
diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
index ae831b6b3e..d60b1b2973 100644
--- a/hw/display/virtio-gpu.c
+++ b/hw/display/virtio-gpu.c
@@ -1166,10 +1166,17 @@ static void virtio_gpu_cursor_bh(void *opaque)
     virtio_gpu_handle_cursor(&g->parent_obj.parent_obj, g->cursor_vq);
 }
 
+static bool scanout_vmstate_after_v2(void *opaque, int version)
+{
+    struct VirtIOGPUBase *base = container_of(opaque, VirtIOGPUBase, scanout);
+    struct VirtIOGPU *gpu = container_of(base, VirtIOGPU, parent_obj);
+
+    return gpu->scanout_vmstate_version >= 2;
+}
+
 static const VMStateDescription vmstate_virtio_gpu_scanout = {
     .name = "virtio-gpu-one-scanout",
-    .version_id = 2,
-    .minimum_version_id = 1,
+    .version_id = 1,
     .fields = (const VMStateField[]) {
         VMSTATE_UINT32(resource_id, struct virtio_gpu_scanout),
         VMSTATE_UINT32(width, struct virtio_gpu_scanout),
@@ -1181,12 +1188,18 @@ static const VMStateDescription vmstate_virtio_gpu_scanout = {
         VMSTATE_UINT32(cursor.hot_y, struct virtio_gpu_scanout),
         VMSTATE_UINT32(cursor.pos.x, struct virtio_gpu_scanout),
         VMSTATE_UINT32(cursor.pos.y, struct virtio_gpu_scanout),
-        VMSTATE_UINT32_V(fb.format, struct virtio_gpu_scanout, 2),
-        VMSTATE_UINT32_V(fb.bytes_pp, struct virtio_gpu_scanout, 2),
-        VMSTATE_UINT32_V(fb.width, struct virtio_gpu_scanout, 2),
-        VMSTATE_UINT32_V(fb.height, struct virtio_gpu_scanout, 2),
-        VMSTATE_UINT32_V(fb.stride, struct virtio_gpu_scanout, 2),
-        VMSTATE_UINT32_V(fb.offset, struct virtio_gpu_scanout, 2),
+        VMSTATE_UINT32_TEST(fb.format, struct virtio_gpu_scanout,
+                            scanout_vmstate_after_v2),
+        VMSTATE_UINT32_TEST(fb.bytes_pp, struct virtio_gpu_scanout,
+                            scanout_vmstate_after_v2),
+        VMSTATE_UINT32_TEST(fb.width, struct virtio_gpu_scanout,
+                            scanout_vmstate_after_v2),
+        VMSTATE_UINT32_TEST(fb.height, struct virtio_gpu_scanout,
+                            scanout_vmstate_after_v2),
+        VMSTATE_UINT32_TEST(fb.stride, struct virtio_gpu_scanout,
+                            scanout_vmstate_after_v2),
+        VMSTATE_UINT32_TEST(fb.offset, struct virtio_gpu_scanout,
+                            scanout_vmstate_after_v2),
         VMSTATE_END_OF_LIST()
     },
 };
@@ -1659,6 +1672,7 @@ static Property virtio_gpu_properties[] = {
     DEFINE_PROP_BIT("blob", VirtIOGPU, parent_obj.conf.flags,
                     VIRTIO_GPU_FLAG_BLOB_ENABLED, false),
     DEFINE_PROP_SIZE("hostmem", VirtIOGPU, parent_obj.conf.hostmem, 0),
+    DEFINE_PROP_UINT8("x-scanout-vmstate-version", VirtIOGPU, scanout_vmstate_version, 2),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/include/hw/virtio/virtio-gpu.h b/include/hw/virtio/virtio-gpu.h
index ed44cdad6b..842315d51d 100644
--- a/include/hw/virtio/virtio-gpu.h
+++ b/include/hw/virtio/virtio-gpu.h
@@ -177,6 +177,7 @@ typedef struct VGPUDMABuf {
 struct VirtIOGPU {
     VirtIOGPUBase parent_obj;
 
+    uint8_t scanout_vmstate_version;
     uint64_t conf_max_hostmem;
 
     VirtQueue *ctrl_vq;
-- 
2.39.2