Salil Mehta <salil.me...@opnsrc.net> writes:
> Hello,
>
> Came across below code excerpt in x86/microvm code and wanted to know
> why 'has_hotpluggable_cpus' flag has been set to 'false' while various
> hot(un)plug APIs have been defined?
>
> static void microvm_class_init(ObjectClass *oc, void *data)
> {
> X86MachineClass *x86mc = X86_MACHINE_CLASS(oc);
> MachineClass *mc = MACHINE_CLASS(oc);
> HotplugHandlerClass *hc = HOTPLUG_HANDLER_CLASS(oc);
>
> mc->init = microvm_machine_state_init;
>
> mc->family = "microvm_i386";
> [...]
> mc->max_cpus = 288;
> mc->has_hotpluggable_cpus = false; --------> This one
> [...]
>From the original commit that added it:
It's a minimalist machine type without PCI nor ACPI support, designed
for short-lived guests. microvm also establishes a baseline for
benchmarking and optimizing both QEMU and guest operating systems,
since it is optimized for both boot time and footprint.
Generally hotplug requires a dance between the VMM and the firmware to
properly shutdown and restart hotplug devices. The principle
communication mechanism for this is ACPI.
>
> /* hotplug (for cpu coldplug) */
> mc->get_hotplug_handler = microvm_get_hotplug_handler;
> hc->pre_plug = microvm_device_pre_plug_cb;
> hc->plug = microvm_device_plug_cb;
> hc->unplug_request = microvm_device_unplug_request_cb;
> hc->unplug = microvm_device_unplug_cb;
> [...]
> }
>
>
> Best regards
> Salil
--
Alex Bennée
Virtualisation Tech Lead @ Linaro
