On 10/10/19 6:05 AM, Peter Krempa wrote:

In addition to Markus' review,

'savevm' was buggy as it considered all monitor-owned block device nodes
for snapshot. With introduction of -blockdev the common usage made all

With the introduction of -blockdev, the common usage

nodes including protocol and backing file nodes monitor-owned and thus

nodes be monitor-owned

considered for snapshot.

This is a problem since the 'file' protocol nodes can't have internal
snapshots and it does not make sense to take snapshot of nodes
representing backing files.

This was fixed by commit 05f4aced658a02b02 clients need to be able to
detect whether this fix is present.

Since savevm does not have an QMP alternative, add the feature for the
'human-monitor-command' backdoor which is used to call this command in
modern use.

Signed-off-by: Peter Krempa <pkre...@redhat.com>
---
  qapi/misc.json | 9 ++++++++-
  1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/qapi/misc.json b/qapi/misc.json
index 6bd11f50e6..5d0070aa43 100644
--- a/qapi/misc.json
+++ b/qapi/misc.json
@@ -1020,6 +1020,12 @@
  #
  # @cpu-index: The CPU to use for commands that require an implicit CPU
  #
+# Features:
+# @savevm-blockdev-monitor-nodes: If present, the HMP command savevm only
+#                                 snapshots monitor-owned nodes if they have no
+#                                 parents. This allows to use 'savevm' with
+#                                 -blockdev. (since 4.2)

s/to use/the use of/

+#
  # Returns: the output of the command as a string
  #
  # Since: 0.14.0
@@ -1047,7 +1053,8 @@
  ##
  { 'command': 'human-monitor-command',
    'data': {'command-line': 'str', '*cpu-index': 'int'},
-  'returns': 'str' }
+  'returns': 'str',
+  'features': [ 'savevm-blockdev-monitor-nodes' ] }

  ##
  # @change:


--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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