Re: [PATCH RFC V2 12/37] hw/acpi: Use qemu_present_cpu() API in ACPI CPU hotplug init

[Gavin Shan]

Hi Salil,

On 9/26/23 20:04, Salil Mehta wrote:
> ACPI CPU Hotplug code assumes a virtual CPU is unplugged if the CPUState object
> is absent in the list of ths possible CPUs(CPUArchIdList *possible_cpus)
> maintained on per-machine basis. Use the earlier introduced qemu_present_cpu()
> API to check this state.
>
> This change should have no bearing on the functionality of any architecture and
> is mere a representational change.
>
> Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
> ---
>   hw/acpi/cpu.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
> index 45defdc0e2..d5ba37b209 100644
> --- a/hw/acpi/cpu.c
> +++ b/hw/acpi/cpu.c
> @@ -225,7 +225,10 @@ void cpu_hotplug_hw_init(MemoryRegion *as, Object *owner,
>       state->dev_count = id_list->len;
>       state->devs = g_new0(typeof(*state->devs), state->dev_count);
>       for (i = 0; i < id_list->len; i++) {
> -        state->devs[i].cpu =  CPU(id_list->cpus[i].cpu);
> +        struct CPUState *cpu = CPU(id_list->cpus[i].cpu);
> +        if (qemu_present_cpu(cpu)) {
> +            state->devs[i].cpu = cpu;
> +        }
>           state->devs[i].arch_id = id_list->cpus[i].arch_id;
>       }
>       memory_region_init_io(&state->ctrl_reg, owner, &cpu_hotplug_ops, state,

I don't think qemu_present_cpu() is needed because all possible vCPUs are 
present
for x86 and arm64 at this point? Besides, we have the assumption all 
hotpluggable
vCPUs are present, looking at James' kernel series where 
ACPI_HOTPLUG_PRESENT_CPU
exists in linux/drivers/acpi/Kconfig :)

Thanks,
Gavin