Re: all class init functions for all types in QEMU are called in select_machine(). Expected?

[Paolo Bonzini]

On 12/03/21 11:25, Claudio Fontana wrote:
> We can register them from there if needed I think,, but where ever we
> do it, we still have to point to the one set of ops or the other,
> depending on the cpu model that is finally chosen.
>
> So when we attach the tcg cpu accelerator object to the cpu, we
> currently should check which cpu it is, and behave accordingly.
>
> Maybe this is better? Ie, not set the tcg ops in different places (in
> the v7m cpu class init and in the tcg cpu accel init),
>
> but rather set them just in a single place, when we attach the accel
> cpu object, checking which cpu profile it is somehow (TBD), and then
> behave accordingly?

Take a look at 
https://wiki.qemu.org/User:Paolo_Bonzini/Machine_init_sequence#Basic_phases. 
 The phases are:

- creating backends (PHASE_NO_MACHINE)

- creating machine (after which PHASE_MACHINE_CREATED is entered)

- creating accelerator (after which PHASE_ACCEL_CREATED is entered)

- initializing embedded devices (in machine_run_board_init, after which 
PHASE_MACHINE_INITIALIZED is entered), including CPUs

- creating devices (in qmp_x_exit_preconfig, after which 
PHASE_MACHINE_READY is entered)

And the last is where the guest actually starts.

I think that you should have a callback in the accelerator that runs 
after -cpu is processed and before PHASE_MACHINE_INITIALIZED is entered. 
 So the right place to add it would be machine_run_board_init.

Maybe some kind of double dispatch, where the accelerator has an 
acc->init_cpu(acc, cc) method and the CPU has a cc->init_tcg_ops(cc) 
method.  Then TCG's init_cpu calls into the latter.

Paolo