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

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

Hi,

On 01/20/2016 06:15 PM, Haozhong Zhang wrote:

> CCing QEMU vNVDIMM maintainer: Xiao Guangrong
>
>> Conceptually, an NVDIMM is just like a fast SSD which is linearly mapped
>> into memory.  I am still on the dom0 side of this fence.
>>
>> The real question is whether it is possible to take an NVDIMM, split it
>> in half, give each half to two different guests (with appropriate NFIT
>> tables) and that be sufficient for the guests to just work.
>>
>
> Yes, one NVDIMM device can be split into multiple parts and assigned
> to different guests, and QEMU is responsible to maintain virtual NFIT
> tables for each part.
>
>> Either way, it needs to be a toolstack policy decision as to how to
>> split the resource.

Currently, we are using NVDIMM as a block device and a DAX-based filesystem
is created upon it in Linux so that file-related accesses directly reach
the NVDIMM device.

In KVM, If the NVDIMM device need to be shared by different VMs, we can
create multiple files on the DAX-based filesystem and assign the file to
each VMs. In the future, we can enable namespace (partition-like) for PMEM
memory and assign the namespace to each VMs (current Linux driver uses the
whole PMEM as a single namespace).

I think it is not a easy work to let Xen hypervisor recognize NVDIMM device
and manager NVDIMM resource.

Thanks!