[Qemu-devel] [PATCH for-1.5] qmp: add query-drive-mirror-capabilities

[Luiz Capitulino <lcapitulino@redhat.com>]

The drive-mirror command was extended in QEMU v1.3.0 with two new
optional arguments 'granularity' and 'buf-size'. However, there's
no way for libvirt to query for the existence of the new arguments.

This commit solves this problem by adding the
query-drive-mirror-capabilities command, which reports the
existence of both arguments.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---

I'm just mimicking query-migrate-capabilities. I don't know if this
is the best way of doing this because we don't allow drive-mirror
capabilities to be set and they're always on.

On the other hand, if we take a simpler approach like returning a
single string of supported new arguments, we may regret it later if
we end up having to support capabilities negotiation.

Having said that, I don't mind doing this one way or the other and
slightly prefer the simpler approach.

 blockdev.c       | 21 +++++++++++++++++++++
 qapi-schema.json | 40 ++++++++++++++++++++++++++++++++++++++++
 qmp-commands.hx  |  7 +++++++
 3 files changed, 68 insertions(+)

diff --git a/blockdev.c b/blockdev.c
index 8a1652b..3fa5ade 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1279,6 +1279,27 @@ void qmp_block_commit(const char *device,
     drive_get_ref(drive_get_by_blockdev(bs));
 }
 
+DriveMirrorCapabilityStatusList *qmp_query_drive_mirror_capabilities(Error **errp)
+{
+    DriveMirrorCapabilityStatusList *caps, *head = NULL;
+    int i;
+
+    for (i = 0; i < DRIVE_MIRROR_CAPABILITY_MAX; i++) {
+        if (head == NULL) {
+            head = g_malloc0(sizeof(*caps));
+            caps = head;
+        } else {
+            caps->next = g_malloc0(sizeof(*caps));
+            caps = caps->next;
+        }
+        caps->value = g_malloc(sizeof(*caps->value));
+        caps->value->capability = i;
+        caps->value->state = true;
+    }
+
+    return head;
+}
+
 #define DEFAULT_MIRROR_BUF_SIZE   (10 << 20)
 
 void qmp_drive_mirror(const char *device, const char *target,
diff --git a/qapi-schema.json b/qapi-schema.json
index 751d3c2..311882d 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1715,6 +1715,46 @@
             '*speed': 'int' } }
 
 ##
+# @DriveMirrorCapability
+#
+# Capabilities supported by the driver-mirror command
+#
+# @granularity: supports setting the dirty bitmap's granularity through the
+#               'granularity' argument
+#
+# @buf-size: supports setting the amount of data to be sent from source
+#            to target through the 'buf-size' argument
+#
+# Since: 1.5.0
+##
+{ 'enum': 'DriveMirrorCapability', 'data': [ 'granularity', 'buf-size' ] }
+
+##
+# @DriveMirrorCapabilityStatus
+#
+# Status of drive-mirror capabilities
+#
+# @capability: capability enumeration
+#
+# @state: True if supported False otherwise
+#
+# Since: 1.5.0
+##
+{ 'type': 'DriveMirrorCapabilityStatus',
+  'data': { 'capability': 'DriveMirrorCapability', 'state': 'bool' } }
+
+##
+# @query-drive-mirror-capabilities
+#
+# Returns information about current drive-mirror's capabilities status
+#
+# Returns: @DriveMirrorCapabilityStatus list
+#
+# Since: 1.5.0
+##
+{ 'command': 'query-drive-mirror-capabilities', 'returns': [ 'DriveMirrorCapabilityStatus' ] }
+
+##
 # @drive-mirror
 #
 # Start mirroring a block device's writes to a new destination.
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 4d65422..5b4e559 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -2715,6 +2715,13 @@ EQMP
     },
 
     {
+        .name       = "query-drive-mirror-capabilities",
+        .args_type  = "",
+        .mhandler.cmd_new = qmp_marshal_input_query_drive_mirror_capabilities,
+    },
+
+
+    {
         .name       = "query-cpu-definitions",
         .args_type  = "",
         .mhandler.cmd_new = qmp_marshal_input_query_cpu_definitions,
-- 
1.8.1.4