qemu-colo.rst: Simplify the block replication setup

On the primary side we don't actually need the replication
block driver, since it only passes trough all IO.
So simplify the setup and also use 'blockdev-add' instead of
'human-monitor-command'.

This is how my clients use colo in production.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Lukas Straub <lukasstraub2@web.de>
Link: https://lore.kernel.org/qemu-devel/20260302-colo_unit_test_multifd-v11-17-d653fb3b1d80@web.de
Signed-off-by: Fabiano Rosas <farosas@suse.de>

docs/system/qemu-colo.rst

@@ -242,8 +242,8 @@ Note:
 **4.** On Primary VM's QEMU monitor, issue command::
 
     {"execute":"qmp_capabilities"}
-    {"execute": "human-monitor-command", "arguments": {"command-line": "drive_add -n buddy driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.2,file.port=9999,file.export=parent0,node-name=replication0"}}
-    {"execute": "x-blockdev-change", "arguments":{"parent": "colo-disk0", "node": "replication0" } }
+    {"execute": "blockdev-add", "arguments": {"driver": "nbd", "node-name": "nbd0", "server": {"type": "inet", "host": "127.0.0.2", "port": "9999"}, "export": "parent0", "detect-zeroes": "on"} }
+    {"execute": "x-blockdev-change", "arguments":{"parent": "colo-disk0", "node": "nbd0" } }
     {"execute": "migrate-set-capabilities", "arguments": {"capabilities": [ {"capability": "x-colo", "state": true } ] } }
     {"execute": "migrate", "arguments": {"uri": "tcp:127.0.0.2:9998" } }
 
@@ -271,7 +271,7 @@ Primary Failover
 The Secondary died, resume on the Primary::
 
     {"execute": "x-blockdev-change", "arguments":{ "parent": "colo-disk0", "child": "children.1"} }
-    {"execute": "human-monitor-command", "arguments":{ "command-line": "drive_del replication0" } }
+    {"execute": "blockdev-del", "arguments": {"node-name": "nbd0"} }
     {"execute": "object-del", "arguments":{ "id": "comp0" } }
     {"execute": "object-del", "arguments":{ "id": "iothread1" } }
     {"execute": "object-del", "arguments":{ "id": "m0" } }
@@ -311,8 +311,8 @@ Wait until disk is synced, then::
     {"execute": "stop"}
     {"execute": "block-job-cancel", "arguments":{ "device": "resync"} }
 
-    {"execute": "human-monitor-command", "arguments":{ "command-line": "drive_add -n buddy driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.2,file.port=9999,file.export=parent0,node-name=replication0"}}
-    {"execute": "x-blockdev-change", "arguments":{ "parent": "colo-disk0", "node": "replication0" } }
+    {"execute": "blockdev-add", "arguments": {"driver": "nbd", "node-name": "nbd0", "server": {"type": "inet", "host": "127.0.0.2", "port": "9999"}, "export": "parent0", "detect-zeroes": "on"} }
+    {"execute": "x-blockdev-change", "arguments":{ "parent": "colo-disk0", "node": "nbd0" } }
 
     {"execute": "object-add", "arguments":{ "qom-type": "filter-mirror", "id": "m0", "netdev": "hn0", "queue": "tx", "outdev": "mirror0" } }
     {"execute": "object-add", "arguments":{ "qom-type": "filter-redirector", "id": "redire0", "netdev": "hn0", "queue": "rx", "indev": "compare_out" } }
@@ -343,8 +343,8 @@ Wait until disk is synced, then::
     {"execute": "stop"}
     {"execute": "block-job-cancel", "arguments":{ "device": "resync" } }
 
-    {"execute": "human-monitor-command", "arguments":{ "command-line": "drive_add -n buddy driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.1,file.port=9999,file.export=parent0,node-name=replication0"}}
-    {"execute": "x-blockdev-change", "arguments":{ "parent": "colo-disk0", "node": "replication0" } }
+    {"execute": "blockdev-add", "arguments": {"driver": "nbd", "node-name": "nbd0", "server": {"type": "inet", "host": "127.0.0.1", "port": "9999"}, "export": "parent0", "detect-zeroes": "on"} }
+    {"execute": "x-blockdev-change", "arguments":{ "parent": "colo-disk0", "node": "nbd0" } }
 
     {"execute": "object-add", "arguments":{ "qom-type": "filter-mirror", "id": "m0", "insert": "before", "position": "id=rew0", "netdev": "hn0", "queue": "tx", "outdev": "mirror0" } }
     {"execute": "object-add", "arguments":{ "qom-type": "filter-redirector", "id": "redire0", "insert": "before", "position": "id=rew0", "netdev": "hn0", "queue": "rx", "indev": "compare_out" } }