[Qemu-devel] [PATCH 2/3] qmp: Expose read-only option for 'change'

[Max Reitz <mreitz@redhat.com>]

Expose the new read-only option of qmp_change_blockdev() for the
'change' QMP command. Leave it unset for HMP for now.

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 hmp.c            |  2 +-
 qapi-schema.json |  7 ++++++-
 qmp-commands.hx  | 24 +++++++++++++++++++++++-
 qmp.c            | 15 ++++++++++++---
 4 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/hmp.c b/hmp.c
index 94b27df..0719fa3 100644
--- a/hmp.c
+++ b/hmp.c
@@ -1133,7 +1133,7 @@ void hmp_change(Monitor *mon, const QDict *qdict)
         }
     }
 
-    qmp_change(device, target, !!arg, arg, &err);
+    qmp_change(device, target, !!arg, arg, false, 0, &err);
     if (err &&
         error_get_class(err) == ERROR_CLASS_DEVICE_ENCRYPTED) {
         error_free(err);
diff --git a/qapi-schema.json b/qapi-schema.json
index 441e001..80aaa63 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1581,6 +1581,10 @@
 #          password to set.  If this argument is an empty string, then no future
 #          logins will be allowed.
 #
+# @read-only: #optional, only valid for block devices. This option allows
+#             changing the read-only mode of the block device; defaults to
+#             'retain'. (Since 2.3)
+#
 # Returns: Nothing on success.
 #          If @device is not a valid block device, DeviceNotFound
 #          If the new block device is encrypted, DeviceEncrypted.  Note that
@@ -1595,7 +1599,8 @@
 # Since: 0.14.0
 ##
 { 'command': 'change',
-  'data': {'device': 'str', 'target': 'str', '*arg': 'str'} }
+  'data': {'device': 'str', 'target': 'str', '*arg': 'str',
+           '*read-only': 'BlockdevChangeReadOnlyMode'} }
 
 ##
 # @ObjectTypeInfo:
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 6ef1b28..edc1783 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -109,7 +109,7 @@ EQMP
 
     {
         .name       = "change",
-        .args_type  = "device:B,target:F,arg:s?",
+        .args_type  = "device:B,target:F,arg:s?,read-only:s?",
         .mhandler.cmd_new = qmp_marshal_input_change,
     },
 
@@ -124,6 +124,8 @@ Arguments:
 - "device": device name (json-string)
 - "target": filename or item (json-string)
 - "arg": additional argument (json-string, optional)
+- "read-only": new read-only mode (json-string, optional)
+          - Possible values: "retain" (default), "ro", "rw", "auto"
 
 Examples:
 
@@ -141,6 +143,26 @@ Examples:
                             "arg": "foobar1" } }
 <- { "return": {} }
 
+3. Load a read-only medium into a writable drive
+
+-> { "execute": "change",
+             "arguments": { "device": "isa-fd0",
+                            "target": "/srv/images/ro.img",
+                            "arg": "raw",
+                            "read-only": "retain" } }
+
+<- { "error":
+     { "class": "GenericError",
+       "desc": "Could not open '/srv/images/ro.img': Permission denied" } }
+
+-> { "execute": "change",
+             "arguments": { "device": "isa-fd0",
+                            "target": "/srv/images/ro.img",
+                            "arg": "raw",
+                            "read-only": "auto" } }
+
+<- { "return": {} }
+
 EQMP
 
     {
diff --git a/qmp.c b/qmp.c
index bd63cf4..d12035b 100644
--- a/qmp.c
+++ b/qmp.c
@@ -397,13 +397,22 @@ static void qmp_change_vnc(const char *target, bool has_arg, const char *arg,
 #endif /* !CONFIG_VNC */
 
 void qmp_change(const char *device, const char *target,
-                bool has_arg, const char *arg, Error **errp)
+                bool has_arg, const char *arg,
+                bool has_read_only, BlockdevChangeReadOnlyMode read_only,
+                Error **errp)
 {
+    if (!has_read_only) {
+        read_only = BLOCKDEV_CHANGE_READ_ONLY_MODE_RETAIN;
+    }
+
     if (strcmp(device, "vnc") == 0) {
+        if (has_read_only) {
+            error_setg(errp, "Parameter 'read-only' is invalid for VNC");
+            return;
+        }
         qmp_change_vnc(target, has_arg, arg, errp);
     } else {
-        qmp_change_blockdev(device, target, arg,
-                            BLOCKDEV_CHANGE_READ_ONLY_MODE_RETAIN, errp);
+        qmp_change_blockdev(device, target, arg, read_only, errp);
     }
 }
 
-- 
1.9.3