Re: [libvirt] [RFC PATCHv2 5/8] threshold: add qemu capability bit

Track whether qemu is new enough to do block thresholds on the active layer. The plan is that even if qemu is too old, the event handler can still be registered, but will never fire (since

it is useful to bulk-install handlers); while the request to set a threshold will honor the capability bit and fail up front if it is not possible. FIXME: Note that qemu requires that libvirt use a node name and not a device name to actually use the feature. What's more, a single qcow2 host resource results in two separate qemu nodes (one node for the guest view served by qcow2 protocol, the other node for the underlying host file access), so I'm working on a patch to qemu to automatically name all nodes (rather than having to hack up libvirt to supply two separate node names for a much more complex command line), at which point I'll need code in libvirt to probe the node name that got assigned by qemu. So I may still need another capability bit for whether qemu is new enough to have the patch to auto-name all nodes.

* src/qemu/qemu_capabilities.h (QEMU_CAPS_BLOCK_WRITE_THRESHOLD): New bit. * src/qemu/qemu_capabilities.c (virQEMUCapsCommands): Enable it. Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- src/qemu/qemu_capabilities.c | 4 +++- src/qemu/qemu_capabilities.h | 3 ++- 2 files changed, 5 insertions(+), 2 deletions(-)