Re: [Qemu-devel] Question about vNVDIMM file format

[Stefan Hajnoczi]

On Mon, May 16, 2016 at 04:04:01PM +0100, Richard W.M. Jones wrote:
> I'm playing with ext4 and DAX.
> 
> I'm using:
> 
>   -object memory-backend-file,id=mem1,share,mem-path=/var/tmp/pmem,size=4G \
>   -device nvdimm,memdev=mem1,id=nv1
> 
> where /var/tmp/pmem is a 4 GB ext4 filesystem image (no partition
> table).  I can mount this in the guest using:
> 
>   mount -o dax /dev/pmem0 /mnt
> 
> and everything appears to work.
> 
> I read in the mailing list that the pmem file has some internal
> structure for storing config data, stored in the last 128 KB of the
> file.  Is that still the case?

AFAICT qemu.git/master does not support the ACPI _DSM for namespace
configuration.  That means the entire /var/tmp/pmem should be visible.

Stefan

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