Re: [PATCH v4 2/4] hw/i386: Attach CPUs to machine

[Igor Mammedov]

On Sat,  5 Feb 2022 13:45:24 +0100
Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:

> Previously CPUs were exposed in the QOM tree at a path
> 
>   /machine/unattached/device[nn]
> 
> where the 'nn' of the first CPU is usually zero, but can
> vary depending on what devices were already created.
> 
> With this change the CPUs are now at
> 
>   /machine/cpu[nn]
> 
> where the 'nn' of the first CPU is always zero.

Could you add to commit message the reason behind the change?


> Note: This (intentionally) breaks compatibility with current
> libvirt code that looks for "/machine/unattached/device[0]"
> in the assumption it is the first CPU.
Why libvirt does this in the first place?

 
> Cc: libvir-list@redhat.com
> Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  hw/i386/x86.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/hw/i386/x86.c b/hw/i386/x86.c
> index b84840a1bb9..50bf249c700 100644
> --- a/hw/i386/x86.c
> +++ b/hw/i386/x86.c
> @@ -108,6 +108,7 @@ void x86_cpu_new(X86MachineState *x86ms, int64_t apic_id, 
> Error **errp)
>  {
>      Object *cpu = object_new(MACHINE(x86ms)->cpu_type);
>  
> +    object_property_add_child(OBJECT(x86ms), "cpu[*]", OBJECT(cpu));

that will take in account only initial cpus, -device/device_add cpus
will still go to wherever device_add attaches them (see qdev_set_id)

>      if (!object_property_set_uint(cpu, "apic-id", apic_id, errp)) {
>          goto out;
>      }