Re: [Qemu-devel] [PATCH v2 06/18] pc: implement NVDIMM device abstract

[Igor Mammedov]

On Wed, 2 Sep 2015 18:36:43 +0800
Xiao Guangrong <address@hidden> wrote:

> 
> 
> On 09/02/2015 05:58 PM, Igor Mammedov wrote:
> > On Fri, 14 Aug 2015 22:51:59 +0800
> > Xiao Guangrong <address@hidden> wrote:
> >
> >> Introduce "pc-nvdimm" device and it has two parameters:
> > Why do you use prefix "pc-", I suppose we potentially
> > could use this device not only with x86 targets but with
> > other targets as well.
> > I'd just drop 'pc' prefix through out patchset.
> 
> Yeah, the prefix is stolen from pc-dimm, will drop this
> prefix as your suggestion.
> 
> >
> >> - @file, which is the backed memory file for NVDIMM device
> > Could you try to split device into backend/frontend parts,
> > like it's done with pc-dimm. As I understand it's preferred
> > way to implement this kind of devices.
> > Then you could reuse memory backends that we already have
> > including file backend.
> 
> I considered it too and Stefan, Paolo got the some idea in
> V1's review, however:
> 
> | However, file-based memory used by NVDIMM is special, it divides the file
> | to two parts, one part is used as PMEM and another part is used to store
> | NVDIMM's configure data.
> |
> | Maybe we can introduce "end-reserved" property to reserve specified size
> | at the end of the file. Or create a new class type based on
> | memory-backend-file (named nvdimm-backend-file) class to hide this magic
> | thing?
I'd go with separate backend/frontend idea.

Question is if this config area is part backend or frontend?
If we pass-through NVDIMM device do we need to set configdata=true
and QEMU would skip building config structures and use structures
that are already present on passed-through device in that place?


> 
> Your idea?
[...]