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

[Xiao Guangrong <guangrong.xiao@linux.intel.com>]

On 01/21/2016 04:18 PM, Jan Beulich wrote:
>>>> On 20.01.16 at 18:17, <guangrong.xiao@linux.intel.com> wrote:
>
>>
>> On 01/21/2016 01:07 AM, Jan Beulich wrote:
>>>>>> On 20.01.16 at 16:29, <guangrong.xiao@linux.intel.com> 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.