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Re: [libvirt] [RFC PATCH 1/2] qemu: caps: Add capability for dynamic 'auto-read-only' support for files

On Fri, Aug 16, 2019 at 04:37:59PM +0200, Peter Krempa wrote:
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: Peter Krempa <pkrempa redhat com>
Reviewed-by: Jiri Denemark <jdenemar redhat com>
src/qemu/qemu_capabilities.c                     | 2 ++
src/qemu/qemu_capabilities.h                     | 1 +
tests/qemucapabilitiesdata/caps_4.1.0.x86_64.xml | 1 +
3 files changed, 4 insertions(+)

diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index c9677315ab..83b1a12d14 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -537,6 +537,7 @@ VIR_ENUM_IMPL(virQEMUCaps,
              /* 335 */
+              "blockdev-file-dynamic-auto-read-only",

The string representation follows the QEMU path


@@ -1281,6 +1282,7 @@ 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;
diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
index 68ef6c49b4..2fe0e26ced 100644
--- a/src/qemu/qemu_capabilities.h
+++ b/src/qemu/qemu_capabilities.h
@@ -518,6 +518,7 @@ typedef enum { /* virQEMUCapsFlags grouping marker for syntax-check */
    /* 335 */
    QEMU_CAPS_DEVICE_BOCHS_DISPLAY, /* -device bochs-display */
    QEMU_CAPS_MIGRATION_FILE_DROP_CACHE, /* migration with disk cache on is safe for type='file' disks */
+    QEMU_CAPS_BLOCK_FILE_AUTO_READONLY_DYNAMIC, /* the auto-read-only property of block backends for files is dynamic */

But the constant has the words in a random order.

It's internal so we can rename it later if needed.

Also, the capability rewrapping script should be capable of handling
two-line comments. (Three lines would require changing it)

    QEMU_CAPS_LAST /* this must always be the last item */
} virQEMUCapsFlags;

Reviewed-by: Ján Tomko <jtomko redhat com>


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