Re: [libvirt] [PATCH 05/11] qemu: block: Use 'auto-read-only' instead of 'read-only' for backing chain

To allow using -blockdev with blockjobs need to reopen files in read-write mode when modifying the backing chain.

To achieve this we need to use 'auto-read-only' for the backing files rather than the normal 'read-only' property. That way qemu knows that the files need to be reopened. Note that the format drivers (e.g. qcow2) are still opened with the read-only property enabled when being a member of the backing chain since they are supposed to be immutable unless a block job is started. QEMU v4.0 allows also dynamic behaviour for auto-read-only which allows us to use sVirt as we only grant write permissions to files when doing a blockjob.

Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- src/qemu/qemu_block.c | 26 ++++++++++++++++--- src/qemu/qemu_block.h | 6 +++--

.../qemu-ns.x86_64-latest.args | 2 +- 39 files changed, 115 insertions(+), 92 deletions(-) diff --git a/src/qemu/qemu_block.c b/src/qemu/qemu_block.c index c9e6af49c9..9abdac5ca3 100644 --- a/src/qemu/qemu_block.c +++ b/src/qemu/qemu_block.c @@ -1027,6 +1027,7 @@ qemuBlockStorageSourceGetBlockdevGetCacheProps(virStorageSourcePtr src, * @src: disk source * @legacy: use legacy formatting of attributes (for -drive / old qemus) * @onlytarget: omit any data which does not identify the image itself + * @autoreadonly: Use the new auto-readonly feature in qemu

* * Creates a JSON object describing the underlying storage or protocol of a * storage source. Returns NULL on error and reports an appropriate error message.