qemu: capabilities: Add detection of the 'savevm' fix for -blockdev

The 'savevm' HMP command didn't work properly with blockdev as it tried
to do snapshot of everything including the protocol nodes accessing
files which are not snapshottable. Qemu fixed this bug so now we need to
detect it to allow enabling blockdev.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

src/qemu/qemu_capabilities.c

@@ -551,6 +551,7 @@ VIR_ENUM_IMPL(virQEMUCaps,
               /* 345 */
               "arm-max-cpu",
               "blockdev-file-dynamic-auto-read-only",
+              "savevm-monitor-nodes",
     );
 
 
@@ -1397,6 +1398,7 @@ static struct virQEMUCapsStringFlags virQEMUCapsQMPSchemaQueries[] = {
     { "nbd-server-add/arg-type/bitmap", QEMU_CAPS_NBD_BITMAP },
     { "blockdev-add/arg-type/+file/drop-cache", QEMU_CAPS_MIGRATION_FILE_DROP_CACHE },
     { "blockdev-add/arg-type/+file/$dynamic-auto-read-only", QEMU_CAPS_BLOCK_FILE_AUTO_READONLY_DYNAMIC },
+    { "human-monitor-command/$savevm-monitor-nodes", QEMU_CAPS_SAVEVM_MONITOR_NODES },
 };
 
 typedef struct _virQEMUCapsObjectTypeProps virQEMUCapsObjectTypeProps;

src/qemu/qemu_capabilities.h

@@ -532,6 +532,7 @@ typedef enum { /* virQEMUCapsFlags grouping marker for syntax-check */
     /* 345 */
     QEMU_CAPS_ARM_MAX_CPU, /* max-arm-cpu type exists */
     QEMU_CAPS_BLOCK_FILE_AUTO_READONLY_DYNAMIC, /* the auto-read-only property of block backends for files is dynamic */
+    QEMU_CAPS_SAVEVM_MONITOR_NODES, /* 'savevm' handles monitor-owned nodes properly */
 
     QEMU_CAPS_LAST /* this must always be the last item */
 } virQEMUCapsFlags;

tests/qemucapabilitiesdata/caps_4.2.0.aarch64.xml

@@ -171,6 +171,7 @@
   <flag name='ramfb'/>
   <flag name='arm-max-cpu'/>
   <flag name='blockdev-file-dynamic-auto-read-only'/>
+  <flag name='savevm-monitor-nodes'/>
   <version>4001050</version>
   <kvmVersion>0</kvmVersion>
   <microcodeVersion>61700242</microcodeVersion>

tests/qemucapabilitiesdata/caps_4.2.0.x86_64.xml

@@ -214,6 +214,7 @@
   <flag name='vhost-user-vga'/>
   <flag name='ramfb'/>
   <flag name='blockdev-file-dynamic-auto-read-only'/>
+  <flag name='savevm-monitor-nodes'/>
   <version>4001092</version>
   <kvmVersion>0</kvmVersion>
   <microcodeVersion>43100242</microcodeVersion>