Re: [Qemu-devel] [PATCH 0/3] Introduce a new --only-migratable option

[Ashijeet Acharya]

On Thu, Dec 15, 2016 at 9:37 PM, Dr. David Alan Gilbert
<address@hidden> wrote:
> * Michael S. Tsirkin (address@hidden) wrote:
>> On Thu, Dec 15, 2016 at 12:36:59AM +0530, Ashijeet Acharya wrote:
>> > This series adds a new command line option "--only-migratable" which will 
>> > only
>> > allow addition of those devices to a QEMU instance which are migratable 
>> > and do
>> > not abruptly fail QEMU after migration.
>> >
>> > Patch 1 adds the new option "-only-migratable".
>> >
>> > Patch 2 adds compatibility for various "device adding" options for both via
>> > command line and hotplug methods.
>> >
>> > Patch 3 handles the special case of devices which become unmigratable 
>> > dynamically
>> > by making call to "migrate_add_blocker". Here we fail the particular 
>> > action of the
>> > device which results in an unmigratable VM.
>> > Eg: 9pfs fails to mount the filesystem.
>>
>> I guess that's possible but wouldn't it be cleaner to add introspection
>> so management can find out what can migrate?
>> Further, what should be removed (e.g. by hotplug) if you do want
>> to migrate.

Actually, I think user never gets to add devices which are
unmigratable in the first place. So there won't be a possibility to
remove them because they never get added in the first place.

>>
>> As it is, you get a failure but no easy way for tools to
>> find out what was the failure reason.
>
> You get the device name of the device that's failed don't you?

Yes, I have included error messages explaining the cause and the name
of the device which failed it. Also, I would like opinions of everyone
on whether they give satisfactory explanation in each case.

Ashijeet

> Where would you add introspection?
>
> Dave
>
>>
>> > Ashijeet Acharya (3):
>> >   migration: Add a new option to enable only-migratable
>> >   migration: Allow "device add" options to only add migratable devices
>> >   migration: disallow migrate_add_blocker during migration
>> >
>> >  block/qcow.c                  | 11 ++++++++++-
>> >  block/vdi.c                   | 11 ++++++++++-
>> >  block/vhdx.c                  | 20 ++++++++++++++------
>> >  block/vmdk.c                  | 12 +++++++++++-
>> >  block/vpc.c                   | 15 ++++++++++++---
>> >  block/vvfat.c                 | 24 ++++++++++++++++--------
>> >  hw/9pfs/9p.c                  | 22 ++++++++++++++++++----
>> >  hw/display/virtio-gpu.c       | 35 ++++++++++++++++++++++-------------
>> >  hw/intc/arm_gic_kvm.c         | 20 ++++++++++++++------
>> >  hw/intc/arm_gicv3_its_kvm.c   | 21 ++++++++++++++-------
>> >  hw/intc/arm_gicv3_kvm.c       | 22 +++++++++++++++-------
>> >  hw/misc/ivshmem.c             | 17 +++++++++++++----
>> >  hw/scsi/vhost-scsi.c          | 27 +++++++++++++++++++++------
>> >  hw/usb/bus.c                  | 15 +++++++++++++++
>> >  hw/virtio/vhost.c             | 11 ++++++++++-
>> >  include/migration/migration.h |  9 ++++++++-
>> >  migration/migration.c         | 42 
>> > ++++++++++++++++++++++++++++++++++++++++--
>> >  qdev-monitor.c                |  9 +++++++++
>> >  qemu-options.hx               | 10 ++++++++++
>> >  stubs/migr-blocker.c          |  3 ++-
>> >  target-i386/kvm.c             | 19 ++++++++++++++++---
>> >  vl.c                          |  4 ++++
>> >  22 files changed, 304 insertions(+), 75 deletions(-)
>> >
>> > --
>> > 2.6.2
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK