From mboxrd@z Thu Jan  1 00:00:00 1970
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: Kernel Oops when reading kernel_page_tables
	debugfs file
Date: Tue, 30 Nov 2010 10:04:21 -0500
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To: Vivien Bernet-Rollande <vbernetr@gmail.com>
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On Tue, Nov 30, 2010 at 10:34:07AM +0100, Vivien Bernet-Rollande wrote:
> On Mon, Nov 29, 2010 at 4:20 PM, Konrad Rzeszutek Wilk
> <konrad.wilk@oracle.com> wrote:
> > On Wed, Nov 24, 2010 at 05:07:49PM +0100, Vivien Bernet-Rollande wrot=
e:
> >> Hi list.
> >> I'm =A0currently trying to get a device driver to work on Xen dom0. =
The driver
> >> maps PCI space to userland, and for some reason I have yet to figure=
, it
> >> doesn't work.
> >
> > Did you set VM_IO on your mapping?
> >
>=20
> The driver doesn't set the VM_IO flag itself. However, it calls
> io_remap_pfn_range(), which is a macro wrapper around
> remap_pfn_range(). The later does :
> vma->vm_flags |=3D VM_IO | VM_RESERVED | VM_PFNMAP;
>=20
> So the VM_IO flag is set. I actually corrected the bug by adding the
> _PAGE_IOMAP flag in the vma->vm_pgprot.

Ah, there is a macro for that: vm_get_page_prot, as so:

vma->vm_page_prot =3D vm_get_page_prot(vma->vm_flags);

And under Xen the vm_get_page_prot will set _PAGE_IOMAP if it detects VM_=
IO flag.
>=20
> Shouldn't remap_pfn_range() set that flag if VM_IO is set ?

Nope. You need to use the above mentioned macro to do it.