On Mon, Jun 12, 2017 at 12:46:09PM +0800, Peter Xu wrote:
> On Fri, Jun 09, 2017 at 03:39:24PM +0200, Markus Armbruster wrote:
> > Peter Xu <pet...@redhat.com> writes:
> >
> > > Let the old man "MigrationState" join the object family. Direct benefit
> > > is that we can start to use all the property features derived from
> > > current QDev, like: HW_COMPAT_* bits, command line setup for migration
> > > parameters (so will never need to set them up each time using HMP/QMP,
> > > this is really, really attractive for test writters), etc.
> > >
> > > I see no reason to disallow this happen yet. So let's start from this
> > > one, to see whether it would be anything good.
> > >
> > > No functional change at all.
> > >
> > > Signed-off-by: Peter Xu <pet...@redhat.com>
> > > ---
> > > include/migration/migration.h | 19 ++++++++++++++
> > > migration/migration.c | 61
> > > ++++++++++++++++++++++++++++---------------
> > > 2 files changed, 59 insertions(+), 21 deletions(-)
> > >
> > > diff --git a/include/migration/migration.h b/include/migration/migration.h
> > > index 79b5484..bd0186c 100644
> > > --- a/include/migration/migration.h
> > > +++ b/include/migration/migration.h
> > > @@ -21,6 +21,7 @@
> > > #include "qapi-types.h"
> > > #include "exec/cpu-common.h"
> > > #include "qemu/coroutine_int.h"
> > > +#include "hw/qdev.h"
> > >
> > > #define QEMU_VM_FILE_MAGIC 0x5145564d
> > > #define QEMU_VM_FILE_VERSION_COMPAT 0x00000002
> > > @@ -49,6 +50,8 @@ enum mig_rp_message_type {
> > > MIG_RP_MSG_MAX
> > > };
> > >
> > > +#define TYPE_MIGRATION "migration"
> > > +
> > > /* State for the incoming migration */
> > > struct MigrationIncomingState {
> > > QEMUFile *from_src_file;
> > > @@ -91,8 +94,24 @@ struct MigrationIncomingState {
> > > MigrationIncomingState *migration_incoming_get_current(void);
> > > void migration_incoming_state_destroy(void);
> > >
> > > +#define MIGRATION_CLASS(klass) \
> > > + OBJECT_CLASS_CHECK(MigrationClass, (klass), TYPE_MIGRATION)
> > > +#define MIGRATION_OBJ(obj) \
> > > + OBJECT_CHECK(MigrationState, (obj), TYPE_MIGRATION)
> > > +#define MIGRATION_GET_CLASS(obj) \
> > > + OBJECT_GET_CLASS(MigrationClass, (obj), TYPE_MIGRATION)
> > > +
> > > +typedef struct MigrationClass {
> > > + /*< private >*/
> > > + DeviceClass parent_class;
> > > +} MigrationClass;
> > > +
> > > struct MigrationState
> > > {
> > > + /*< private >*/
> > > + DeviceState parent_obj;
> > > +
> > > + /*< public >*/
> >
> > Turning MigrationState into a QOM object so you can use QOM
> > infrastructure makes sense. But why turn it into a device? It doesn't
> > feel device-like to me. Would ObjectClass and Object instead of
> > DeviceClass and DeviceState do?
>
> Yeah. That's the main reason for the series to be (was) RFC.
>
> I was trying to use the HW_COMPAT_* bits and -global, and that's QDev
> thing (IIUC you got that already :). I am just curious about why that
> is not for QObject from the very beginning, then it'll be easier.
>
> For now, IMHO QDev is okay as well for migration, as long as it's kept
> internally inside QEMU. But sure at least I should turn user_creatable
> to off. I'll investigate more to see how to make this a safer approach
> in next post.
We could allow non-device QOM objects use the global property
system optionally.
We could make qdev_prop_set_globals() work on any Object*, and
let QOM classes call it on post_init if they want to be
configurable by global properties too.
Note that this would break qdev_prop_check_globals(), because it
expects globals to work only on TYPE_DEVICE. We could address
that by introducing a new interface type to indicate the type
works with -global (something like
INTERFACE_CONFIGURABLE_BY_GLOBAL_PROPERTIES, but shorter?).
Such a system would probably allow us to replace
default_machine_opts, default_boot_order, default_display,
default_ram_size (and probably many other compat fields) on
MachineClass. It could also be used to implement -machine and
-accel options by simply translating them to global properties
(like we already do for -cpu).
(This sounds like reinventing a QemuOpts-like system on top of
global properties. Maybe that's a bad thing, maybe that's a good
thing. I'm not sure.)
> [...]
--
Eduardo
