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Date: Thu, 19 Aug 2010 14:04:27 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] Re: [PATCH] Fix bug for vcpu hotplug
References: <BC00F5384FCFC9499AF06F92E8B78A9E0B0007F9DC@shsmsx502.ccr.corp.intel.com>	<4C67D844.5060306@redhat.com>	<BC00F5384FCFC9499AF06F92E8B78A9E164C8CB831@shsmsx502.ccr.corp.intel.com>
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To: Avi Kivity <avi@redhat.com>
Cc: "Liu, Jinsong" <jinsong.liu@intel.com>, "Yang,
	Sheng" <sheng.yang@intel.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "kvm@vger.kernel.org" <kvm@vger.kernel.org>, "Li, Xin" <xin.li@intel.com>

On 08/19/2010 10:34 AM, Avi Kivity wrote:
>  On 08/19/2010 06:24 PM, Anthony Liguori wrote:
>> On 08/18/2010 02:33 AM, Avi Kivity wrote:
>>>  On 08/18/2010 10:17 AM, Liu, Jinsong wrote:
>>>> During test, we found qemu-kvm has a bug result in guestos shutdown 
>>>> when vcpu hotadd.
>>>> This patch is to fix the bug, allow hotplug for sysbus qdev.
>>>>
>>>> --- a/hw/qdev.c
>>>> +++ b/hw/qdev.c
>>>> @@ -108,6 +108,7 @@ DeviceState *qdev_create(BusState *bus, const 
>>>> char *name)
>>>>       if (!bus) {
>>>>           if (!main_system_bus) {
>>>>               main_system_bus = qbus_create(&system_bus_info, NULL, 
>>>> "main-system-bus");
>>>> +            main_system_bus->allow_hotplug = 1;
>>>>           }
>>>>           bus = main_system_bus;
>>>>       }
>>>
>>>
>>> Looks reasonable to me.
>>
>> Not really to me.
>>
>> SysBus does not support hotplugging and CPU hot plug shouldn't have 
>> anything to do with qdev hotplug.
>>
>> Can you explain a bit more why this is needed?
>>
>
> On cpu hotplug an apic is added, and apics live on main_system_bus.

That's the problem then.  An APIC does not live on any bus and that's 
where the problem ought to be fixed.

Regards,

Anthony Liguori