Re: [Xen-devel] Re: [PATCH v2] xen/gntdev, gntalloc: Remove unneeded VM flags

Konrad Rzeszutek Wilk
Wed, 09 Mar 2011 17:05:34 -0000

> > @@ -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?