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

[Michael S. Tsirkin]

On Mon, Oct 19, 2015 at 06:01:17PM +0800, Xiao Guangrong wrote:
> 
> 
> On 10/19/2015 05:46 PM, Igor Mammedov wrote:
> >On Mon, 19 Oct 2015 12:17:22 +0300
> >"Michael S. Tsirkin" <address@hidden> 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.
> 
> 
> 
> 

It does seem to add a bunch of devices in ACPI and memory regions in
memory space.
Whatever your device is, it's generally safe to assume that most
people don't need it.

-- 
MST