Re: [PATCHv7 05/26] vfio: introduce the VFIO_DMA_MAP_FLAG_NOEXEC flag

[Alex Williamson <alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On Tue, 2014-09-23 at 16:21 -0600, Alex Williamson wrote:
> On Tue, 2014-09-23 at 16:46 +0200, Antonios Motakis wrote:
> > We introduce the VFIO_DMA_MAP_FLAG_NOEXEC flag to the VFIO dma map call,
> > and expose its availability via the capability VFIO_IOMMU_PROT_NOEXEC.
> > This way the user can control whether the XN flag will be set on the
> > requested mappings. The IOMMU_NOEXEC flag needs to be available for all
> > the IOMMUs of the container used.
> > 
> > Signed-off-by: Antonios Motakis <a.motakis-lrHrjnjw1UfHK3s98zE1ajGjJy/sRE9J@public.gmane.org>
> > ---
> >  include/uapi/linux/vfio.h | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > index 6612974..30f630c 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -29,6 +29,7 @@
> >   * capability is subject to change as groups are added or removed.
> >   */
> >  #define VFIO_DMA_CC_IOMMU		4
> > +#define VFIO_IOMMU_PROT_NOEXEC		5
> 
> Can't we advertise this as a flag bit in vfio_iommu_type1_info instead?

Ok, I see in the next patch that it's pretty similar to
VFIO_DMA_CC_IOMMU, so the check extension is probably correct for
determining the current state.  Maybe we could name it more similarly,
VFIO_DMA_NOEXEC_IOMMU.  I guess the intended usage is that once a user
attaches a group to the container they can query whether the
VFIO_DMA_MAP_FLAG_NOEXEC is valid.  Ok.  Thanks,

Alex

> Also, EEH already took 5 as seen immediately below.
> 
> >  
> >  /* Check if EEH is supported */
> >  #define VFIO_EEH			5
> > @@ -401,6 +402,7 @@ struct vfio_iommu_type1_dma_map {
> >  	__u32	flags;
> >  #define VFIO_DMA_MAP_FLAG_READ (1 << 0)		/* readable from device */
> >  #define VFIO_DMA_MAP_FLAG_WRITE (1 << 1)	/* writable from device */
> > +#define VFIO_DMA_MAP_FLAG_NOEXEC (1 << 2)	/* not executable from device */
> >  	__u64	vaddr;				/* Process virtual address */
> >  	__u64	iova;				/* IO virtual address */
> >  	__u64	size;				/* Size of mapping (bytes) */
> 
>