Re: [PATCH 2/2] pc-nvdimm acpi: build ACPI tables for pc-nvdimm devices

[Haozhong Zhang <haozhong.zhang@intel.com>]

On 01/04/16 16:01, Stefano Stabellini wrote:
> CC'ing the Xen tools maintainers and Anthony.
> 
> On Tue, 29 Dec 2015, Haozhong Zhang wrote:
> > Reuse existing NVDIMM ACPI code to build ACPI tables for pc-nvdimm
> > devices. The resulting tables are then copied into Xen guest domain so
> > tha they can be later loaded by Xen hvmloader.
> > 
> > Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
> 
> How much work would it be to generate the nvdimm acpi tables from the
> Xen toolstack?
>
I think at least two parts of work should be done if generating nvdimm
ACPI tables from toolstack:

(1) An AML builder.
    NVDIMM SSDT table contains a part of definition block, so an AML
    builder is required. If guest ACPI tables is going to be generated
    from toolstack, I think we can port QEMU's AML builder to
    toolstack.

(2) Interface to pass information of vNVDIMM devices from QEMU to Xen.
    Currently, QEMU is responsible to decide the slot IDs of vNVDIMM
    devices, the address space where vNVDIMM devices are mapped to and
    other stuffs that need to be written in ACPI tables. In the
    future, there could be more as planed, including information about
    NVDIMM label areas. If generating NVDIMM ACPI tables from Xen, all
    those information should be passed from QEMU.  Maybe we can pass
    them through xenstore.

> Getting the tables from QEMU doesn't seem like a good idea to me, unless
> we start getting the whole set of ACPI tables that way.
>
As most of current and future vNVDIMM implementation in QEMU would be
related to ACPI, I really want to reuse those code as much as possible.

Haozhong