Re: [Qemu-devel] [RFC PATCH v4 01/11] exec: Remove cpu from cpus list during cpu_exec_exit()

[Zhu Guihua <zhugh.fnst@cn.fujitsu.com>]

On 11/12/2015 05:30 PM, Bharata B Rao wrote:
> On Thu, Nov 12, 2015 at 05:11:02PM +0800, Zhu Guihua wrote:
>> Hi Bharata,
>>
>> On 09/09/2015 03:56 PM, Bharata B Rao wrote:
>>> On Wed, Sep 09, 2015 at 03:41:30PM +0800, Zhu Guihua wrote:
>>>> On 09/09/2015 01:52 PM, Bharata B Rao wrote:
>>>>> On Fri, Sep 04, 2015 at 03:31:24PM +1000, David Gibson wrote:
>>>>>> On Thu, Aug 06, 2015 at 10:57:07AM +0530, Bharata B Rao wrote:
>>>>>>> CPUState *cpu gets added to the cpus list during cpu_exec_init(). It
>>>>>>> should be removed from cpu_exec_exit().
>>>>>>>
>>>>>>> cpu_exec_init() is called from generic CPU::instance_finalize and some
>>>>>>> archs like PowerPC call it from CPU unrealizefn. So ensure that we
>>>>>>> dequeue the cpu only once.
>>>>>>>
>>>>>>> Instead of introducing a new field CPUState.queued, I could have used
>>>>>>> CPUState.cpu_index to check if the cpu is already dequeued from the list.
>>>>>>> Since that doesn't work for CONFIG_USER_ONLY, I had to add a new field.
>>>>>>>
>>>>>>> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
>>>>>> This seems reasonable to me, but I'm wondering how x86 cpu hotplug /
>>>>>> unplug is working without it.
>>>>> x86 hotplug/unplug code currently resides in Zhu's git tree
>>>>> (git://github.com/zhugh/qemu). They are removing the CPU from the list
>>>>> explicitly in x86 CPU's instance_finalize routine.
>>>> Sorry, my git tree is git://github.com/zhuguihua/qemu
>>>>
>>>> Now there was no progress about topology, so we don't know what will happen
>>>> in x86. I am not sure whether we will take this method finally.
>>> Andreas had a presentation on this topic in KVM forum recently.
>>>
>>> Andreas - do you have any updates on the topology and other aspects
>>> of CPU hotplug so that we can align the CPU hotplug work in different
>>> archs accordingly and hope to get it merged in 2.5 time frame ?
>> Do you update the patchset?
>>
>> My work in x86 has stopped for a while, Maybe I can get some ideas from
>> another
>> arch's worker.
> My last version is here:
> https://lists.gnu.org/archive/html/qemu-devel/2015-08/msg00650.html
>
> I initally started with core level CPU hotplug, moved to socket level hotplug
> based on Andreas' patchset and then moved back again to core level hotplug.
>
> I was a bit confused about how the generic semantics would evovle and hence
> the work got delayed. I wil be posting the next version of my patchset
> based on core level semantics soon.
>
> I am hoping that I should be able to get CPU hotplug/unplug included
> in QEMU-2.6 timeframe.
>
Thanks for your reply. Look forward to your next version.

Regards,
Zhu