Re: [libvirt] [PATCH 31/32] qemu: Use the 'device_id' property of SCSI disks to avoid regressing

On Mon, Jan 28, 2019 at 05:19:00PM +0100, Peter Krempa wrote: > QEMU accidentally exposed the id of -drive (or same value as disk > serial, if provided) in one of the identifiers visible from the guest. > > To avoid regression in case when -blockdev will be used we need to > always specify it ourselves. > > Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; > --- > src/qemu/qemu_command.c | 22 +++++++++++++++++++ > .../controller-virtio-scsi.x86_64-latest.args | 20 ++++++++--------- > .../disk-cache.x86_64-latest.args | 4 ++-- > .../disk-scsi-device-auto.x86_64-latest.args | 3 ++- > .../disk-scsi.x86_64-latest.args | 16 ++++++++------ > .../disk-shared.x86_64-latest.args | 5 +++-- > ...threads-virtio-scsi-pci.x86_64-latest.args | 4 ++-- > 7 files changed, 50 insertions(+), 24 deletions(-)

I rather wish there was a way we could avoid exposing the alias ID to every guest forever more. QEMU could achieve that with machine type versioning, so that it only exposes the drive ID to guests with legacy machine types for sake of backport. We need to explicitly set this though, as with -blockdev QEMU can't do the right thing for legacy machine types as it lacks tie drive ID entirely. Once we set it, we enable it for non-legacy machine types too :-( Annoyingly I don't see a way out of this mess such that libvirt only enables the back compat for existing guests.