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

On Tue, Jan 29, 2019 at 16:06:35 +0000, Daniel Berrange wrote: > 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. Do you mean that for any new machine type we should not put the -drive ID as the 'device_id' property? AFAIK qemu should now handle that correctly by not creating any ID. In that case we could tie -blockdev to the new machine type only and thus will not need to add any code to format the backward compatibility stuff.