RE: [PATCH V8 3/8] hw/acpi: Update ACPI GED framework to support vCPU Hotplug

[Salil Mehta <salil.mehta@huawei.com>]

Hello,

Sorry, I missed this earlier.

>  From: Zhao Liu <zhao1.liu@intel.com>
>  Sent: Wednesday, March 13, 2024 6:14 AM
>  To: Salil Mehta <salil.mehta@huawei.com>
>  
>  Hi Salil,
>  
>  It seems my comment [1] in v7 was missed, but I still hit the same issue. Pls
>  let me paste the previous comment here again.
>  
>  [1]: https://lore.kernel.org/qemu-devel/ZXCqp32ggIFvUweu@intel.com/

Yes, I have this in my mind. 

>  
>  [snip]
>  
>  > @@ -400,6 +411,12 @@ static void acpi_ged_initfn(Object *obj)
>  >      memory_region_init_io(&ged_st->regs, obj, &ged_regs_ops, ged_st,
>  >                            TYPE_ACPI_GED "-regs", ACPI_GED_REG_COUNT);
>  >      sysbus_init_mmio(sbd, &ged_st->regs);
>  > +
>  > +    memory_region_init(&s->container_cpuhp, OBJECT(dev), "cpuhp
>  container",
>  > +                       ACPI_CPU_HOTPLUG_REG_LEN);
>  > +    sysbus_init_mmio(SYS_BUS_DEVICE(dev), &s->container_cpuhp);
>  > +    cpu_hotplug_hw_init(&s->container_cpuhp, OBJECT(dev),
>  > +                        &s->cpuhp_state, 0);
>  >  }
>  >
>  
>  I find this cpu_hotplug_hw_init() can still cause qtest errors (for v8) on x86
>  platforms as you mentioned in v6:
>  https://lore.kernel.org/qemu-devel/15e70616-6abb-63a4-17d0-
>  820f4a254607@opnsrc.net/T/#m108f102b2fe92b7dd7218f2f942f7b233a9d6a
>  f3
>  
>  IIUC, microvm machine has its own 'possible_cpus_arch_ids' and that is
>  inherited from its parent x86 machine.
>  
>  The above error is because device-introspect-test sets the none-machine:
>  
>  # starting QEMU: exec ./qemu-system-i386 -qtest unix:/tmp/qtest-
>  3094820.sock -qtest-log /dev/null -chardev socket,path=/tmp/qtest-
>  3094820.qmp,id=char0 -mon chardev=char0,mode=control -display none -
>  audio none -nodefaults -machine none -accel qtest
>  
>  So what about just checking mc->possible_cpu_arch_ids instead of an
>  assert in cpu_hotplug_hw_init()?
>  
>  diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c index
>  4b24a2500361..303f1f1f57bc 100644
>  --- a/hw/acpi/cpu.c
>  +++ b/hw/acpi/cpu.c
>  @@ -221,7 +221,10 @@ void cpu_hotplug_hw_init(MemoryRegion *as,
>  Object *owner,
>       const CPUArchIdList *id_list;
>       int i;
>  
>  -    assert(mc->possible_cpu_arch_ids);
>  +    if (!mc->possible_cpu_arch_ids) {
>  +        return;
>  +    }
>  +


Yes, we can do this with some debug print or trace maybe.


>       id_list = mc->possible_cpu_arch_ids(machine);
>       state->dev_count = id_list->len;
>       state->devs = g_new0(typeof(*state->devs), state->dev_count);
>  
>  This check seems to be acceptable in the general code path? Not all
>  machines have possible_cpu_arch_ids, after all.

True. BTW, have you tested this with Qtest?

Thanks
Salil.