Re: [PATCH 5/6] xen-gntalloc: Userspace grant allocation driver

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Thu, Jan 27, 2011 at 01:52:10PM -0500, Konrad Rzeszutek Wilk wrote:
> On Fri, Jan 21, 2011 at 10:59:07AM -0500, Daniel De Graaf wrote:
> > This allows a userspace application to allocate a shared page for
> > implementing inter-domain communication or device drivers. These
> > shared pages can be mapped using the gntdev device or by the kernel
> > in another domain.
> > 
> > Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> > ---
> >  drivers/xen/Kconfig    |    8 +
> >  drivers/xen/Makefile   |    2 +
> >  drivers/xen/gntalloc.c |  477 ++++++++++++++++++++++++++++++++++++++++++++++++
> >  include/xen/gntalloc.h |   70 +++++++
> >  4 files changed, 557 insertions(+), 0 deletions(-)
> >  create mode 100644 drivers/xen/gntalloc.c
> >  create mode 100644 include/xen/gntalloc.h
> > 
> > diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
> > index 07bec09..a3d7afb 100644
> > --- a/drivers/xen/Kconfig
> > +++ b/drivers/xen/Kconfig
> > @@ -80,6 +80,14 @@ config XEN_GNTDEV
> >  	help
> >  	  Allows userspace processes to use grants.
> >  
> > +config XEN_GRANT_DEV_ALLOC
> > +	tristate "User-space grant reference allocator driver"
> > +	depends on XEN
> > +	help
> > +	  Allows userspace processes to create pages with access granted
> > +	  to other domains. This can be used to implement frontend drivers
> > +	  or as part of an inter-domain shared memory channel.


> > +
> >  config XEN_PLATFORM_PCI
> >  	tristate "xen platform pci device driver"
> >  	depends on XEN_PVHVM && PCI
> > diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
> > index 5088cc2..9585a1d 100644
> > --- a/drivers/xen/Makefile
> > +++ b/drivers/xen/Makefile
> > @@ -10,6 +10,7 @@ obj-$(CONFIG_XEN_XENCOMM)	+= xencomm.o
> >  obj-$(CONFIG_XEN_BALLOON)	+= balloon.o
> >  obj-$(CONFIG_XEN_DEV_EVTCHN)	+= xen-evtchn.o
> >  obj-$(CONFIG_XEN_GNTDEV)	+= xen-gntdev.o
> > +obj-$(CONFIG_XEN_GRANT_DEV_ALLOC)	+= xen-gntalloc.o
> >  obj-$(CONFIG_XENFS)		+= xenfs/
> >  obj-$(CONFIG_XEN_SYS_HYPERVISOR)	+= sys-hypervisor.o
> >  obj-$(CONFIG_XEN_PLATFORM_PCI)	+= xen-platform-pci.o
> > @@ -18,5 +19,6 @@ obj-$(CONFIG_XEN_DOM0)		+= pci.o
> >  
> >  xen-evtchn-y			:= evtchn.o
> >  xen-gntdev-y				:= gntdev.o
> > +xen-gntalloc-y				:= gntalloc.o
> >  
> >  xen-platform-pci-y		:= platform-pci.o
> > diff --git a/drivers/xen/gntalloc.c b/drivers/xen/gntalloc.c
> > new file mode 100644
> > index 0000000..a230dc4
> > --- /dev/null
> > +++ b/drivers/xen/gntalloc.c
> > @@ -0,0 +1,477 @@
> > +/******************************************************************************
> > + * gntalloc.c
> > + *
> > + * Device for creating grant references (in user-space) that may be shared
> > + * with other domains.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with this program; if not, write to the Free Software
> > + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
> > + */
> > +
> > +/*
> > + * This driver exists to allow userspace programs in Linux to allocate kernel
> > + * memory that will later be shared with another domain.  Without this device,
> > + * Linux userspace programs cannot create grant references.

Why can't this be done in gntdev? Is there a simple test program for this?