qemu: caps: Add capability for dynamic 'auto-read-only' support for files

Initial implementation of 'auto-read-only' didn't reopen the backing
files when needed. For '-blockdev' to work we need to be able to tel
qemu to open a file read-only and change it during blockjobs as we label
backing chains with a sVirt label which does not allow writing. The
dynamic auto-read-only supports this as it reopens files when writing
is demanded.

Add a capability to detect that the posix file based backends support
the dynamic part.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

src/qemu/qemu_capabilities.c

@@ -550,6 +550,7 @@ VIR_ENUM_IMPL(virQEMUCaps,
 
               /* 345 */
               "arm-max-cpu",
+              "blockdev-file-dynamic-auto-read-only",
     );
 
 
@@ -1395,6 +1396,7 @@ static struct virQEMUCapsStringFlags virQEMUCapsQMPSchemaQueries[] = {
     { "query-display-options/ret-type/+egl-headless/rendernode", QEMU_CAPS_EGL_HEADLESS_RENDERNODE },
     { "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 },
 };
 
 typedef struct _virQEMUCapsObjectTypeProps virQEMUCapsObjectTypeProps;

src/qemu/qemu_capabilities.h

@@ -531,6 +531,7 @@ 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_LAST /* this must always be the last item */
 } virQEMUCapsFlags;

tests/qemucapabilitiesdata/caps_4.1.0.x86_64.xml

@@ -212,6 +212,7 @@
   <flag name='vhost-user-gpu'/>
   <flag name='vhost-user-vga'/>
   <flag name='ramfb'/>
+  <flag name='blockdev-file-dynamic-auto-read-only'/>
   <version>4001000</version>
   <kvmVersion>0</kvmVersion>
   <microcodeVersion>43100241</microcodeVersion>

tests/qemucapabilitiesdata/caps_4.2.0.aarch64.xml

@@ -170,6 +170,7 @@
   <flag name='vhost-user-gpu'/>
   <flag name='ramfb'/>
   <flag name='arm-max-cpu'/>
+  <flag name='blockdev-file-dynamic-auto-read-only'/>
   <version>4001050</version>
   <kvmVersion>0</kvmVersion>
   <microcodeVersion>61700242</microcodeVersion>

tests/qemucapabilitiesdata/caps_4.2.0.ppc64.xml

@@ -173,6 +173,7 @@
   <flag name='vhost-user-gpu'/>
   <flag name='vhost-user-vga'/>
   <flag name='machine.pseries.cap-ccf-assist'/>
+  <flag name='blockdev-file-dynamic-auto-read-only'/>
   <version>4001050</version>
   <kvmVersion>0</kvmVersion>
   <microcodeVersion>42900242</microcodeVersion>

tests/qemucapabilitiesdata/caps_4.2.0.s390x.xml

@@ -132,6 +132,7 @@
   <flag name='vhost-user-gpu'/>
   <flag name='query-cpu-model-baseline'/>
   <flag name='query-cpu-model-comparison'/>
+  <flag name='blockdev-file-dynamic-auto-read-only'/>
   <version>4001050</version>
   <kvmVersion>0</kvmVersion>
   <microcodeVersion>39100242</microcodeVersion>

tests/qemucapabilitiesdata/caps_4.2.0.x86_64.xml

@@ -213,6 +213,7 @@
   <flag name='vhost-user-gpu'/>
   <flag name='vhost-user-vga'/>
   <flag name='ramfb'/>
+  <flag name='blockdev-file-dynamic-auto-read-only'/>
   <version>4001092</version>
   <kvmVersion>0</kvmVersion>
   <microcodeVersion>43100242</microcodeVersion>