From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

The audio migration vmstate is empty, and always has been; we can't
just remove it though because an old qemu might send it us.
Changes with -audiodev now mean it's sometimes created when it didn't
used to be, and can confuse migration to old qemu.

Change it so that vmstate_audio is never sent; if it's received it
should still be accepted, and old qemu's shouldn't be too upset if it's
missing.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 audio/audio.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/audio/audio.c b/audio/audio.c
index 59453ef856..54a153c0ef 100644
--- a/audio/audio.c
+++ b/audio/audio.c
@@ -1622,10 +1622,20 @@ void audio_cleanup(void)
     }
 }
 
+static bool vmstate_audio_needed(void *opaque)
+{
+    /*
+     * Never needed, this vmstate only exists in case
+     * an old qemu sends it to us.
+     */
+    return false;
+}
+
 static const VMStateDescription vmstate_audio = {
     .name = "audio",
     .version_id = 1,
     .minimum_version_id = 1,
+    .needed = vmstate_audio_needed,
     .fields = (VMStateField[]) {
         VMSTATE_END_OF_LIST()
     }
-- 
2.31.1

On Mon, Aug 09, 2021 at 06:09:56PM +0100, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> The audio migration vmstate is empty, and always has been; we can't
> just remove it though because an old qemu might send it us.
> Changes with -audiodev now mean it's sometimes created when it didn't
> used to be, and can confuse migration to old qemu.
> 
> Change it so that vmstate_audio is never sent; if it's received it
> should still be accepted, and old qemu's shouldn't be too upset if it's
> missing.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Queued for 6.1

thanks,
  Gerd

"Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>
> The audio migration vmstate is empty, and always has been; we can't
> just remove it though because an old qemu might send it us.
> Changes with -audiodev now mean it's sometimes created when it didn't
> used to be, and can confuse migration to old qemu.
>
> Change it so that vmstate_audio is never sent; if it's received it
> should still be accepted, and old qemu's shouldn't be too upset if it's
> missing.
>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>