From mboxrd@z Thu Jan  1 00:00:00 1970
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: [RFC Design Doc] Add vNVDIMM support for Xen
Date: Thu, 18 Feb 2016 21:14:20 -0500
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> > > QEMU would always use MFN above guest normal ram and I/O holes for
> > > vNVDIMM. It would attempt to search in that space for a contiguous range
> > > that is large enough for that that vNVDIMM devices. Is guest able to
> > > punch holes in such GFN space?
> > 
> > See XENMAPSPACE_* and their uses.
> > 
> 
> I think we can add following restrictions to avoid uses of XENMAPSPACE_*
> punching holes in GFNs of vNVDIMM:
> 
> (1) For XENMAPSPACE_shared_info and _grant_table, never map idx in them
>     to GFNs occupied by vNVDIMM.

OK, that sounds correct.
>     
> (2) For XENMAPSPACE_gmfn, _gmfn_range and _gmfn_foreign,
>    (a) never map idx in them to GFNs occupied by vNVDIMM, and
>    (b) never map idx corresponding to GFNs occupied by vNVDIMM

Would that mean that guest xen-blkback or xen-netback wouldn't
be able to fetch data from the GFNs? As in, what if the HVM guest
that has the NVDIMM also serves as a device domain - that is it
has xen-blkback running to service other guests?

> 
> 
> Haozhong