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

[Eduardo Habkost]

On Thu, Jul 14, 2016 at 02:16:39PM -0400, Bandan Das wrote:
> Eduardo Habkost <address@hidden> writes:
> 
> > 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.
> 
> Or just let pc_find_cpu_slot universally set it to -1 since
> this series assumes that -1 means index isn't valid.

I think it would be more intuitive if pc_find_cpu_slot() didn't
touch *idx if no slot is found. But both ways sound good to me.

-- 
Eduardo