docs: domain: Clarify on the dangers of migrating with hyperv-passthrough enabled

Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
index 0c5e33c78fe2e5363d029272b4b9fd29caa298c1..2e9c4506069d31a4e04235a09bd53750440f2608 100644 (file)
--- a/docs/formatdomain.rst
+++ b/docs/formatdomain.rst
@@ -1929,7 +1929,14 @@ are:
       Set exactly the specified features.
 
    ``passthrough``
-      Enable all features currently supported by the hypervisor.
+      Enable all features currently supported by the hypervisor, even those that
+      libvirt does not understand. Migration of a guest using passthrough is
+      dangerous if the source and destination hosts are not identical in both
+      hardware, QEMU version, microcode version and configuration. If such a
+      migration is attempted then the guest may hang or crash upon resuming
+      execution on the destination host. Depending on hypervisor version the
+      virtual CPU may or may not contain features which may block migration
+      even to an identical host.
 
    The ``mode`` attribute can be omitted and will default to ``custom``.