Re: [Qemu-devel] [PATCH V3 4/7] pc: add cpu hotplug handler to PC_MACHINE

[Igor Mammedov]

On Mon, 29 Sep 2014 10:58:04 +0800
Gu Zheng <address@hidden> wrote:

> Hi Igor,
> On 09/26/2014 09:06 PM, Igor Mammedov wrote:
> 
> > On Wed, 17 Sep 2014 09:24:00 +0800
> > Gu Zheng <address@hidden> wrote:
> > 
> >> Add cpu hotplug handler to PC_MACHINE, which will perform the acpi
> >> cpu hotplug callback via hotplug_handler API.
> >>
> >> v3:
> >>  -deal with start up cpus in a more neat way as Igor suggested.
> >> v2:
> >>  -just rebase.
> >>
> >> Signed-off-by: Gu Zheng <address@hidden>
> >> ---
> >>  hw/i386/pc.c |   26 +++++++++++++++++++++++++-
> >>  1 files changed, 25 insertions(+), 1 deletions(-)
> >>
> >> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> >> index b6c9b61..e25e71b 100644
> >> --- a/hw/i386/pc.c
> >> +++ b/hw/i386/pc.c
> >> @@ -1613,11 +1613,34 @@ out:
> >>      error_propagate(errp, local_err);
> >>  }
> >>  
> >> +static void pc_cpu_plug(HotplugHandler *hotplug_dev,
> >> +                        DeviceState *dev, Error **errp)
> >> +{
> >> +    HotplugHandlerClass *hhc;
> >> +    Error *local_err = NULL;
> >> +    PCMachineState *pcms = PC_MACHINE(hotplug_dev);
> >> +
> >> +    if (!pcms->acpi_dev) {
> >> +        if (dev->hotplugged) {
> >> +            error_setg(&local_err,
> >> +                       "cpu hotplug is not enabled: missing acpi
> >> device");
> >> +        }
> >> +        goto out;
> >> +    }
> >> +
> >> +    hhc = HOTPLUG_HANDLER_GET_CLASS(pcms->acpi_dev);
> >> +    hhc->plug(HOTPLUG_HANDLER(pcms->acpi_dev), dev, &local_err);
> > above call this would rise SCI unconditionally whether CPU is
> > hotplugged or not.
> 
> Above precheck can avoid this, startup CPUs won't run into this: 
>     if (!pcms->acpi_dev) {
>         if (dev->hotplugged) {
>             error_setg(&local_err,
>                        "cpu hotplug is not enabled: missing acpi
> device"); }
>         goto out;
>     }
that's true, but it robs plug handler of initializing startup CPUs'
state in acpi_dev and leads to code duplication between
AcpiCpuHotplug_init() and acpi_cpu_plug_cb().

> 
> Thanks,
> Gu
> 
> > perhaps checking for this in acpi_cpu_plug_cb() and rising IRQ only
> > for hotplugged CPUs would be better.
> > 
> >> +out:
> >> +    error_propagate(errp, local_err);
> >> +}
> >> +
> >>  static void pc_machine_device_plug_cb(HotplugHandler *hotplug_dev,
> >>                                        DeviceState *dev, Error
> >> **errp) {
> >>      if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
> >>          pc_dimm_plug(hotplug_dev, dev, errp);
> >> +    } else if (object_dynamic_cast(OBJECT(dev), TYPE_CPU)) {
> >> +        pc_cpu_plug(hotplug_dev, dev, errp);
> >>      }
> >>  }
> >>  
> >> @@ -1626,7 +1649,8 @@ static HotplugHandler
> >> *pc_get_hotpug_handler(MachineState *machine, {
> >>      PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(machine);
> >>  
> >> -    if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
> >> +    if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM) ||
> >> +        object_dynamic_cast(OBJECT(dev), TYPE_CPU)) {
> >>          return HOTPLUG_HANDLER(machine);
> >>      }
> >>  
> > 
> > .
> > 
> 
>