Re: [Qemu-devel] [PATCH v2 0/7] Qemu virtio pmem device

[Pankaj Gupta]

> >> 
> >> Ok, if it works, we could list those regions? and change pmem0 mode to dax
> >> mode, right?
> >
> >You mean fs dax?
> >I don't think currently we support this because raw image wont have any
> >metadata.
> >Will have to think if this is at all possible or how we can achieve such
> >behavior.
> >
> 
> Ok, I got it.
> 
> >Also, there is requirement to support host backing file on real NVDIMM and
> >virtio. Once we have have first version of virtio pmem series merged
> >upstream
> >we will continue to work on advance features depending upon feasibility.
> >
> 
> One curiosity, what difference make NVDIMM backend doesn't work now?
> 
> The /dev/dax0.0 is a char file. The nvdimm device use mmap to map HVA to HPA.
> It looks a normal file to me. Would appreciated it if you would share some
> light on it.
> 

It will require support of MAP_SYNC at host side without an explicit 
flush/fsync.
We need to add the usecase in both guest and host drivers/device. Also, thorough
testing is required to fix any issues. 

I will do the required changes for the next step. 

Thanks,
Pankaj