On Wed, Nov 18, 2020 at 04:43:19PM +0100, Paolo Bonzini wrote: > Il mer 18 nov 2020, 16:26 Eduardo Habkost <ehabk...@redhat.com> ha scritto: > > > > > > The alternative is to store the (type, function) tuple directly, with the > > > type as a string. Then you can just use type_init. > > > > Right. Let's build on top of that: > > > > Another alternative would be to store a (type, X86CPUAccel) tuple > > directly, with the type as string. This would save the extra > > indirection of the x86_cpu_accel_init() call. > > > > It turns out we already have a mechanism to register and store > > (type, StructContainingFunctionPointers) tuples at initialization > > time: QOM. > > > > X86CPUAccel can become X86CPUAccelClass, and be registered as a > > QOM type. It could be a subtype of TYPE_ACCEL or not, it > > shouldn't matter. > > > > It would be a weird type that isn't instantiated, and/or that does nothing > but monkey patching other classes. I don't think it's a good fit.
The whole point of this would be to avoid monkey patching other classes. Why wouldn't we instantiate it? There's a huge number of static variables in target/i386/kvm.c that could be moved to that object. Sounds like a perfect fit for me. I won't try to stop you if you really want to invent a brand new (name => CollectionOfFunctionPointers) registry, but it seems unnecessary. > > Yet another possibility is to use GHashTable. It is limited to one value > per key, but it's enough if everything is kept local to {hw,target}/i386. > If needed a new function pointer can be added to MachineClass, implemented > in X86MachineState (where the GHashTable would also be) and called in > accel.c. > > Paolo > > Paolo > > > > I remember this was suggested in a previous thread, but I don't > > remember if there were any objections. > > > > > > > > > Making sure module_call_init() is called at the correct moment is > > > > not easier or safer than just making sure accel_init_machine() > > > > (or another init function you create) is called at the correct > > > > moment. > > > > > > Since there is a way to do it without a new level, that would of course > > be > > > fine for me too. Let me explain however why I think Claudio's design had > > > module_call_init() misplaced and what the fundamental difference is. The > > > basic phases in qemu_init() are: > > > > > > - initialize stuff > > > - parse command line > > > - create machine > > > - create accelerator > > > - initialize machine > > > - create devices > > > - start > > > > > > with a mess of other object creation sprinkled between the various phases > > > (but we don't care about those). > > > > > > What I object to, is calling module_call_init() after the "initialize > > stuff" > > > phase. Claudio was using it to call the function directly, so it had to > > be > > > exactly at "create accelerator". This is different from all other > > > module_call_init() calls, which are done very early. > > > > I agree. > > > > > > > > With the implementation I sketched, accel_register_call must still be > > done > > > after type_init, so there's still an ordering constraint, but all it's > > doing > > > is registering a callback in the "initialize stuff" phase. > > > > Makes sense, if we really want to introduce a new accel_register_call() > > abstraction. I don't think we need it, though. > > > > -- > > Eduardo > > > > -- Eduardo