vfio: ccw: basic implementation for vfio_ccw driver

To make vfio support subchannel devices, we need a css driver for
the vfio subchannels. This patch adds a basic vfio-ccw subchannel
driver for this purpose.

To enable VFIO for vfio-ccw, enable S390_CCW_IOMMU config option
and configure VFIO as required.

Acked-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Message-Id: <20170317031743.40128-5-bjsdjshi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
diff --git a/arch/s390/include/asm/isc.h b/arch/s390/include/asm/isc.h
index 68d7d68..8a0b721 100644
--- a/arch/s390/include/asm/isc.h
+++ b/arch/s390/include/asm/isc.h
@@ -16,6 +16,7 @@
 #define CONSOLE_ISC 1			/* console I/O subchannel */
 #define EADM_SCH_ISC 4			/* EADM subchannels */
 #define CHSC_SCH_ISC 7			/* CHSC subchannels */
+#define VFIO_CCW_ISC IO_SCH_ISC		/* VFIO-CCW I/O subchannels */
 /* Adapter interrupts. */
 #define QDIO_AIRQ_ISC IO_SCH_ISC	/* I/O subchannel in qdio mode */
 #define PCI_ISC 2			/* PCI I/O subchannels */