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





On 01/21/2016 04:18 PM, Jan Beulich wrote:
On 20.01.16 at 18:17, <guangrong.xiao@xxxxxxxxxxxxxxx> wrote:


On 01/21/2016 01:07 AM, Jan Beulich wrote:
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

The 2) is PBLK.

entity controls which of the two modes get used (and perhaps for
which parts of the overall NVDIMM).

So i think the "normal" you mentioned is about PMEM. :)

Yes. But then - other than you said above - it still looks to me as
if the split between PMEM and PBLK is arranged for by firmware?

Yes. But OS/Hypervisor is not excepted to dynamically change its configure 
(re-split),
i,e, for PoV of OS/Hypervisor, it is static.

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