Re: [Qemu-devel] [PATCH v3 22/32] nvdimm: init the address region used by NVDIMM ACPI

[Xiao Guangrong <guangrong.xiao@linux.intel.com>]

On 10/19/2015 05:46 PM, Igor Mammedov wrote:
> On Mon, 19 Oct 2015 12:17:22 +0300
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
>
>> On Mon, Oct 19, 2015 at 03:44:13PM +0800, Xiao Guangrong wrote:
>>>
>>>
>>> On 10/19/2015 03:39 PM, Michael S. Tsirkin wrote:
>>>> On Mon, Oct 19, 2015 at 03:27:21PM +0800, Xiao Guangrong wrote:
>>>>>>> +        nvdimm_init_memory_state(&pcms->nvdimm_memory,
>>>>>>> system_memory, machine,
>>>>>>> +                                 TARGET_PAGE_SIZE);
>>>>>>> +
>>>>>>
>>>>>> Shouldn't this be conditional on presence of the nvdimm device?
>>>>>>
>>>>>
>>>>> We will enable hotplug on nvdimm devices in the near future once
>>>>> Linux driver is ready. I'd keep it here for future development.
>>>>
>>>> No, I don't think we should add stuff unconditionally. If not
>>>> nvdimm, some other flag should indicate user intends to hotplug
>>>> things.
>>>>
>>>
>>> Actually, it is not unconditionally which is called if parameter
>>> "-m aaa, maxmem=bbb" (aaa < bbb) is used. It is on the some path of
>>> memoy-hotplug initiation.
>>>
>>
>> Right, but that's not the same as nvdimm.
>>
>
> it could be pc-machine property, then it could be turned on like this:
>   -machine nvdimm_support=on

Er, I do not understand why this separate switch is needed and why nvdimm
and pc-dimm is different. :(

NVDIMM reuses memory-hotplug's framework, such as maxmem, slot, and dimm
device, even some of ACPI logic to do hotplug things, etc. Both nvdimm
and pc-dimm are built on the same infrastructure.