Re: [Qemu-devel] [PATCH v4 04/16] pc: forbid BSP removal

[Igor Mammedov]

On Thu, 14 Jul 2016 14:54:53 -0300
Eduardo Habkost <address@hidden> wrote:

> On Thu, Jul 14, 2016 at 06:54:33PM +0200, Igor Mammedov wrote:
> > BSP is assumed to always present in QEMU code, so
> > untile that assumptions are gone, deny removal request.
> > In another words QEMU won't support BSP hot-unplug.
> > 
> > Signed-off-by: Igor Mammedov <address@hidden>
> > ---
> >  hw/i386/pc.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> > index 5a67f15..33c5f97 100644
> > --- a/hw/i386/pc.c
> > +++ b/hw/i386/pc.c
> > @@ -1751,10 +1751,17 @@ out:
> >  static void pc_cpu_unplug_request_cb(HotplugHandler *hotplug_dev,
> >                                       DeviceState *dev, Error **errp)
> >  {
> > +    int idx;
> >      HotplugHandlerClass *hhc;
> >      Error *local_err = NULL;
> >      PCMachineState *pcms = PC_MACHINE(hotplug_dev);
> >  
> > +    pc_find_cpu_slot(pcms, CPU(dev), &idx);  
> 
> Looks fragile: if one day we create any TYPE_CPU object that is
> not in possible_cpus array, idx is undefined. I suggest
> initializing idx to -1 above.
not that we expect that ever happen, but it won't hurt to
initialize it to -1.

> 
> I can change it when committing, if that's OK for you.
sounds good to me, thanks.

> 
> 
> > +    if (idx == 0) {
> > +        error_setg(&local_err, "1st CPU (BSP) is unpluggable");
> > +        goto out;
> > +    }
> > +
> >      hhc = HOTPLUG_HANDLER_GET_CLASS(pcms->acpi_dev);
> >      hhc->unplug_request(HOTPLUG_HANDLER(pcms->acpi_dev), dev, &local_err);
> >  
> > -- 
> > 2.7.4
> >   
>