Re: Resetting non-qdev children in a 3-phase reset device

[Peter Maydell]

On Mon, 26 Apr 2021 at 10:23, Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>
> On 4/25/21 8:33 PM, Peter Maydell wrote:
> > On Sat, 24 Apr 2021 at 14:04, Philippe Mathieu-Daudé <f4bug@amsat.org> 
> > wrote:
> >> I now understand better the diag288 case, but I still don't understand
> >> the TYPE_APIC one. It has no DeviceClass::reset(), its abstract parent
> >> TYPE_APIC_COMMON register apic_reset_common() but being TYPE_DEVICE it
> >> is not on a qbus. It is somehow connected to the X86CPU object, but the
> >> single call to apic_init_reset() is from do_cpu_init() - not a reset
> >> method -.
> >
> > pc_machine_reset() calls device_legacy_reset(cpu->apic_state)
> > which is to say it invokes the DeviceState::reset method,
> > which is either kvm_apic_reset or apic_reset_common.
>
> Oh, thanks! I guess "convoluted" is the proper adjective to describe
> this reset logic. I suppose APIC is a very old device, part of the
> Frankenstein PC, so hard to rework (because we are scared of the
> implications of changing old & heavily used devices).

This is mostly just another instance of "our reset logic doesn't
deal well with devices which aren't on buses". The APIC isn't on a bus,
so the machine that uses it has a local workaround to manually arrange
for it to reset, just as it does for the CPU.

thanks
-- PMM