Re: [Qemu-devel] [PULL 30/47] acpi nvdimm: fix device physical address base

[Xiao Guangrong]

On 10/31/2016 06:56 PM, Igor Mammedov wrote:
> On Mon, 31 Oct 2016 17:23:31 +0800
> Xiao Guangrong <address@hidden> wrote:
>
> > On 10/31/2016 05:20 PM, Igor Mammedov wrote:
> > > On Sun, 30 Oct 2016 23:24:46 +0200
> > > "Michael S. Tsirkin" <address@hidden> wrote:
> > >
> > > > From: Xiao Guangrong <address@hidden>
> > > >
> > > > According to ACPI 6.0  spec, "Memory Device Physical Address
> > > > Region Base" in memdev is defined as "This field provides the
> > > > Device Physical Address base of the region". This field should
> > > > be zero in our case
> > > I'm not sure that it should be a zero,
> > > care to point source which tells that it should be zero?
> >
> > The spec says that this is the Device Physical Address, so that
> > it is the device internal address, it should be zero as we do not
> > reserve any thing in device internal and we do not have no memory
> > interleave.
> spec says (ACPI 6.1: 5.2.25.3 NVDIMM Region Mapping Structure):
> "NVDIMM Physical Address Region Base":
>   "The base physical address within the NVDIMM of the NVDIMM region."
>
> and nothing more than that so it's hard to come to conclusion that
> it's internal address nor it is offset as you treat it here
> (structure has 'Region Offset' for that).

I think it is clear as the spec says "_within_ the NVDIMM", it is
even more clear than ACPI 6.0 (5.2.25.2 Memory Device to System Physical
Address Range Mapping Structure), in that, it says:
 "In bytes. This field provides the Device Physical Address
  base of the region."

In the namespace spec (http://pmem.io/documents/NVDIMM_Namespace_Spec.pdf),
the explanation to DPA in page 9:
   "DIMM Physical Address: A memory address from a DIMM’s perspective,
   that is, the offset into the DIMM’s memory, starting 
with DPA zero
   as the lowest addressable byte of the DIMM.