[libvirt] [PATCH 21/21] qemu: caps: Add capability for dynamic 'auto-read-only' support for files

[Peter Krempa]

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.
---
 src/qemu/qemu_capabilities.c                     | 4 ++++
 src/qemu/qemu_capabilities.h                     | 3 +++
 tests/qemucapabilitiesdata/caps_4.0.0.x86_64.xml | 1 +
 3 files changed, 8 insertions(+)

diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index da90cd666e..4b851a6e89 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -526,6 +526,9 @@ VIR_ENUM_IMPL(virQEMUCaps,
               "scsi-disk.device_id",
               "virtio-pci-non-transitional",
               "overcommit",
+
+              /* 330 */
+              "blockdev-file-dynamic-auto-read-only",
     );


@@ -1265,6 +1268,7 @@ static struct virQEMUCapsStringFlags virQEMUCapsQMPSchemaQueries[] = {
     { "block-commit/arg-type/*top",  QEMU_CAPS_ACTIVE_COMMIT },
     { "query-iothreads/ret-type/poll-max-ns", QEMU_CAPS_IOTHREAD_POLLING },
     { "query-display-options/ret-type/+egl-headless/rendernode", QEMU_CAPS_EGL_HEADLESS_RENDERNODE },
+    { "blockdev-add/arg-type/+file/$dynamic-auto-read-only", QEMU_CAPS_BLOCK_FILE_AUTO_READONLY_DYNAMIC },
 };

 typedef struct _virQEMUCapsObjectTypeProps virQEMUCapsObjectTypeProps;
diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
index fd7bec7589..b207142fdb 100644
--- a/src/qemu/qemu_capabilities.h
+++ b/src/qemu/qemu_capabilities.h
@@ -509,6 +509,9 @@ typedef enum { /* virQEMUCapsFlags grouping marker for syntax-check */
     QEMU_CAPS_VIRTIO_PCI_TRANSITIONAL, /* virtio *-pci-{non-}transitional devices */
     QEMU_CAPS_OVERCOMMIT, /* -overcommit */

+    /* 330 */
+    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;

diff --git a/tests/qemucapabilitiesdata/caps_4.0.0.x86_64.xml b/tests/qemucapabilitiesdata/caps_4.0.0.x86_64.xml
index 00f2a1cb55..dd77b67456 100644
--- a/tests/qemucapabilitiesdata/caps_4.0.0.x86_64.xml
+++ b/tests/qemucapabilitiesdata/caps_4.0.0.x86_64.xml
@@ -201,6 +201,7 @@
   <flag name='scsi-disk.device_id'/>
   <flag name='virtio-pci-non-transitional'/>
   <flag name='overcommit'/>
+  <flag name='blockdev-file-dynamic-auto-read-only'/>
   <version>3001092</version>
   <kvmVersion>0</kvmVersion>
   <microcodeVersion>43100758</microcodeVersion>
-- 
2.20.1