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

[Igor Mammedov]

On Mon, 31 Oct 2016 19:09:07 +0800
Xiao Guangrong <address@hidden> wrote:

> 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."
It would be less confusing if spec would say
 "starting offset of NVDIMM region within the NVDIMM"
(at least that's how I read it now after looking at 6.0 and 
NVDIMM_Namespace_Spec.pdf)
as "base physical address" is not defined/described in ACPI spec.


> 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.