On 12/8/20 3:01 PM, Peter Krempa wrote:
The validation callback always fetched a fresh copy of 'qemuCaps' to use for validation which is wrong in cases when the VM is already running, such as device hotplug. The newly-fetched qemuCaps may contain flags which weren't originally in use when starting the VM e.g. on a libvirtd upgrade. Since the post-parse/validation machinery has a per-run 'parseOpaque' field filled with qemuCaps of the actual process we can reuse the caps in cases when we get them. The code still fetches a fresh copy if parseOpaque doesn't have a per-run copy to preserve existing functionality. Signed-off-by: Peter Krempa <pkrempa@xxxxxxxxxx> --- src/qemu/qemu_validate.c | 30 ++++++++++++++++++++---------- 1 file changed, 20 insertions(+), 10 deletions(-)
So this will use the old qemuCaps even though a feature might already be available in qemu but libvirt didn't detect it. For instance the virtio-pmem I'm implementing - guests started today won't have the qemuCap for virtio-pmem because it's not implemented yet. But when they update libvirt they still won't get the feature because we're using old qemuCaps for validation and thus new memory model will be denied because of lacking capability.
I can see the value in when we have to chose between old and new style of doing things, but I worry it will kill new features.
Michal
