Re: [Xen-devel] [PATCH 4/4] hvmloader: add support to load extra ACPI tables from qemu

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 20.01.16 at 16:29, <guangrong.xiao@xxxxxxxxxxxxxxx> wrote:
> On 01/20/2016 07:20 PM, Jan Beulich wrote:
>> To answer this I need to have my understanding of the partitioning
>> being done by firmware confirmed: If that's the case, then "normal"
>> means the part that doesn't get exposed as a block device (SSD).
>> In any event there's no correlation to guest exposure here.
> 
> Firmware does not manage NVDIMM. All the operations of nvdimm are handled
> by OS.
> 
> Actually, there are lots of things we should take into account if we move
> the NVDIMM management to hypervisor:
> a) ACPI NFIT interpretation
>     A new ACPI table introduced in ACPI 6.0 is named NFIT which exports the
>     base information of NVDIMM devices which includes PMEM info, PBLK
>     info, nvdimm device interleave, vendor info, etc. Let me explain it one
>     by one.
> 
>     PMEM and PBLK are two modes to access NVDIMM devices:
>     1) PMEM can be treated as NV-RAM which is directly mapped to CPU's address
>        space so that CPU can r/w it directly.
>     2) as NVDIMM has huge capability and CPU's address space is limited, 
> NVDIMM
>        only offers two windows which are mapped to CPU's address space, the 
> data
>        window and access window, so that CPU can use these two windows to 
> access
>        the whole NVDIMM device.

You fail to mention PBLK. The question above really was about what
entity controls which of the two modes get used (and perhaps for
which parts of the overall NVDIMM).

Jan


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