[libvirt] [PATCH 0/8] logically memory hotplug via guest agent

[zhang bo]

On 2015/6/9 20:47, Daniel P. Berrange wrote:

> On Tue, Jun 09, 2015 at 02:12:39PM +0200, Peter Krempa wrote:
>> On Tue, Jun 09, 2015 at 13:05:35 +0100, Daniel Berrange wrote:
>>> On Tue, Jun 09, 2015 at 02:03:13PM +0200, Peter Krempa wrote:
>>>> On Tue, Jun 09, 2015 at 12:46:27 +0100, Daniel Berrange wrote:
>>>>> On Tue, Jun 09, 2015 at 01:22:49PM +0200, Peter Krempa wrote:
>>>>>> On Tue, Jun 09, 2015 at 11:05:16 +0100, Daniel Berrange wrote:
>>>>>>> On Tue, Jun 09, 2015 at 05:33:24PM +0800, Zhang Bo wrote:
>>>>>>
>>
>> ...
>>
>>>>>> 2) The guest OS sometimes needs to enable the memory region after ACPI
>>>>>> memory hotplug. The GA would be able to online such memory. For this
>>>>>> option we don't need to go through a different API though since it can
>>>>>> be compounded using a flag.
>>>>>
>>>>> So, are you saying that we should not be adding this to the
>>>>> virDomainSetMemory API as done in this series, and we should
>>>>> instead be able to request automatic enabling/disabling of the
>>>>> regions when we do the original DIMM hotplug ?
>>>>
>>>> Well, that's the only place where using the memory region GA apis would
>>>> make sense for libvirt.
>>>>
>>>> Whether we should do it is not that clear. Windows does online the
>>>> regions automatically and I was told that some linux distros do it via
>>>> udev rules.
>>>
>>> What do we do in the case of hotunplug currently ? Are we expectig the
>>> guest admin to have manually offlined the regions before doing hotunplug
>>> on the host ?
>>
>> You don't need to offline them prior to unplug. The guest OS handles
>> that automatically when it receives the request.
> 
> Hmm, so if the guest can offline and online DIMMS automatically on
> hotplug/unplug, then I'm puzzelled what value this patch series
> really adds.
> 
> 
> Regards,
> Daniel


Thank you for your reply.
Before this patch, we needed to manually online memory blocks inside the guest, after dimm memory hotplug
for most *nix OSes. (Windows guests automatically get their memory blocks online after hotplugging)
That is to say, we need to LOGICALLY hotplug memory after PHYSICAL hotplug. 
This patch did the LOGICAL part.
With this patch, we don't need to get into the guest to manually online them anymore, which is even 
impossible for most host administrators.



-- 
Oscar    
oscar.zhangbo at huawei.com