migration/multifd: Add a compat property for TLS termination

We're currently changing the way the source multifd migration handles
the shutdown of the multifd channels when TLS is in use to perform a
clean termination by calling gnutls_bye().

Older src QEMUs will always close the channel without terminating the
TLS session. New dst QEMUs treat an unclean termination as an error.

Add multifd_clean_tls_termination (default true) that can be switched
on the destination whenever a src QEMU <= 9.2 is in use.

(Note that the compat property is only strictly necessary for src
QEMUs older than 9.1. Due to synchronization coincidences, src QEMUs
9.1 and 9.2 can put the destination in a condition where it doesn't
see the unclean termination. Still, make the property more inclusive
to facilitate potential backports.)

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 254cc20c4c..02cff735b3 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -42,6 +42,7 @@ GlobalProperty hw_compat_9_2[] = {
     { "virtio-balloon-pci-transitional", "vectors", "0" },
     { "virtio-balloon-pci-non-transitional", "vectors", "0" },
     { "virtio-mem-pci", "vectors", "0" },
+    { "migration", "multifd-clean-tls-termination", "false" },
 };
 const size_t hw_compat_9_2_len = G_N_ELEMENTS(hw_compat_9_2);