From mboxrd@z Thu Jan  1 00:00:00 1970
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: Re: [PATCH v2] xen/gntdev, gntalloc: Remove
	unneeded VM flags
Date: Wed, 9 Mar 2011 12:05:34 -0500
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To: Ian Campbell <Ian.Campbell@eu.citrix.com>
Cc: Daniel De Graaf <dgdegra@tycho.nsa.gov>, "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
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> > @@ -471,8 +483,6 @@ static int gntalloc_mmap(struct file *filp, struct vm_area_struct *vma)
> >  	vma->vm_private_data = gref;
> >  
> >  	vma->vm_flags |= VM_RESERVED;
> > -	vma->vm_flags |= VM_DONTCOPY;
> > -	vma->vm_flags |= VM_PFNMAP | VM_PFN_AT_MMAP;

So the gntalloc driver can be used on PV. You remove the DONTCOPY,PFNMAP, and PFN_AT_MMAP
.. while

> > -	vma->vm_flags |= VM_RESERVED|VM_DONTCOPY|VM_DONTEXPAND|VM_PFNMAP;
> > +	vma->vm_flags |= VM_RESERVED|VM_DONTEXPAND;
> > +
> > +	if (use_ptemod)
> > +		vma->vm_flags |= VM_DONTCOPY|VM_PFNMAP;
> >  

Here (gntdev) you are more careful. Should we do the same check under PV
for the gntalloc driver?

Have you tested this driver in PV <-> HVM env?