From: Fiona Ebner <f.ebner@proxmox.com>

Migration from an 8.2 or 9.0 binary to an 8.1 binary with machine
version 8.1 can fail with:

> kvm: Features 0x1c0010130afffa7 unsupported. Allowed features: 0x10179bfffe7
> kvm: Failed to load virtio-net:virtio
> kvm: error while loading state for instance 0x0 of device '0000:00:12.0/virtio-net'
> kvm: load of migration failed: Operation not permitted

The series

53da8b5a99 virtio-net: Add support for USO features
9da1684954 virtio-net: Add USO flags to vhost support.
f03e0cf63b tap: Add check for USO features
2ab0ec3121 tap: Add USO support to tap device.

only landed in QEMU 8.2, so the compatibility flags should be part of
machine version 8.1.

Moving the flags unfortunately breaks forward migration with machine
version 8.1 from a binary without this patch to a binary with this
patch.

Fixes: 53da8b5a99 ("virtio-net: Add support for USO features")
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
 hw/core/machine.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 8d6dc69f0e..f5dffea33d 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -51,15 +51,15 @@ GlobalProperty hw_compat_8_1[] = {
     { "ramfb", "x-migrate", "off" },
     { "vfio-pci-nohotplug", "x-ramfb-migrate", "off" },
     { "igb", "x-pcie-flr-init", "off" },
+    { TYPE_VIRTIO_NET, "host_uso", "off"},
+    { TYPE_VIRTIO_NET, "guest_uso4", "off"},
+    { TYPE_VIRTIO_NET, "guest_uso6", "off"},
 };
 const size_t hw_compat_8_1_len = G_N_ELEMENTS(hw_compat_8_1);
 
 GlobalProperty hw_compat_8_0[] = {
     { "migration", "multifd-flush-after-each-section", "on"},
     { TYPE_PCI_DEVICE, "x-pcie-ari-nextfn-1", "on" },
-    { TYPE_VIRTIO_NET, "host_uso", "off"},
-    { TYPE_VIRTIO_NET, "guest_uso4", "off"},
-    { TYPE_VIRTIO_NET, "guest_uso6", "off"},
 };
 const size_t hw_compat_8_0_len = G_N_ELEMENTS(hw_compat_8_0);
 
-- 
2.35.3