diff --git a/docs/hyperv.txt b/docs/hyperv.txt
index e53c581f45..a51953daa8 100644
--- a/docs/hyperv.txt
+++ b/docs/hyperv.txt
@@ -209,8 +209,11 @@ In some cases (e.g. during development) it may make sense to use QEMU in
 'pass-through' mode and give Windows guests all enlightenments currently
 supported by KVM. This pass-through mode is enabled by "hv-passthrough" CPU
 flag.
-Note: enabling this flag effectively prevents migration as supported features
-may differ between target and destination.
+Note: "hv-passthrough" flag only enables enlightenments which are known to QEMU
+(have corresponding "hv-*" flag) and copies "hv-spinlocks="/"hv-vendor-id="
+values from KVM to QEMU. "hv-passthrough" overrides all other "hv-*" settings on
+the command line. Also, enabling this flag effectively prevents migration as the
+list of enabled enlightenments may differ between target and destination hosts.
 
 
 4. Useful links