Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

channel I/O mechanism described here, there are various other methods

(like the diag interface). These are out of the scope of this document.

The s390 common I/O layer also provides access to some devices that are

not strictly considered I/O devices. They are considered here as well,

although they are not the focus of this document.

Some additional information can also be found in the kernel source under

Documentation/s390/driver-model.txt.

The css bus

===========

The css bus contains the subchannels available on the system. They fall

into several categories:

* Standard I/O subchannels, for use by the system. They have a child

  device on the ccw bus and are described below.

* I/O subchannels bound to the vfio-ccw driver. See

  Documentation/s390/vfio-ccw.txt.

* Message subchannels. No Linux driver currently exists.

* CHSC subchannels (at most one). The chsc subchannel driver can be used

  to send asynchronous chsc commands.

* eADM subchannels. Used for talking to storage class memory.

The ccw bus

===========

Generic interfaces

==================

Some interfaces are available to other drivers that do not necessarily

have anything to do with the busses described above, but still are

indirectly using basic infrastructure in the common I/O layer. One

example is the support for adapter interrupts.

The following section contains interfaces in use not only by drivers

dealing with ccw devices, but drivers for various other s390 hardware

as well.

Adapter interrupts

------------------

The common I/O layer provides helper functions for dealing with adapter

interrupts and interrupt vectors.

.. kernel-doc:: drivers/s390/cio/airq.c

   :export:

	select ARCH_USE_BUILTIN_BSWAP

	select ARCH_USE_CMPXCHG_LOCKREF

	select ARCH_WANTS_DYNAMIC_TASK_STRUCT

	select ARCH_WANTS_PROT_NUMA_PROT_NONE

	select ARCH_WANTS_UBSAN_NO_NULL

	select ARCH_WANT_IPC_PARSE_VERSION

	select BUILDTIME_EXTABLE_SORT

	  If unsure, say Y.

config KERNEL_NOBP

	def_bool n

	prompt "Enable modified branch prediction for the kernel by default"

	help

	  If this option is selected the kernel will switch to a modified

	  branch prediction mode if the firmware interface is available.

	  The modified branch prediction mode improves the behaviour in

	  regard to speculative execution.

	  With the option enabled the kernel parameter "nobp=0" or "nospec"

	  can be used to run the kernel in the normal branch prediction mode.

	  With the option disabled the modified branch prediction mode is

	  enabled with the "nobp=1" kernel parameter.

	  If unsure, say N.

config EXPOLINE

	def_bool n

	prompt "Avoid speculative indirect branches in the kernel"

	help

	  Compile the kernel with the expoline compiler options to guard

	  against kernel-to-user data leaks by avoiding speculative indirect

	  branches.

	  Requires a compiler with -mindirect-branch=thunk support for full

	  protection. The kernel may run slower.

	  If unsure, say N.

choice

	prompt "Expoline default"

	depends on EXPOLINE

	default EXPOLINE_FULL

config EXPOLINE_OFF

	bool "spectre_v2=off"

config EXPOLINE_MEDIUM

	bool "spectre_v2=auto"

config EXPOLINE_FULL

	bool "spectre_v2=on"

endchoice

endmenu

menu "Memory setup"

cflags-$(CONFIG_WARN_DYNAMIC_STACK) += -mwarn-dynamicstack

endif

ifdef CONFIG_EXPOLINE

  ifeq ($(call cc-option-yn,$(CC_FLAGS_MARCH) -mindirect-branch=thunk),y)

    CC_FLAGS_EXPOLINE := -mindirect-branch=thunk

    CC_FLAGS_EXPOLINE += -mfunction-return=thunk

    CC_FLAGS_EXPOLINE += -mindirect-branch-table

    export CC_FLAGS_EXPOLINE

    cflags-y += $(CC_FLAGS_EXPOLINE)

  endif

endif

ifdef CONFIG_FUNCTION_TRACER

# make use of hotpatch feature if the compiler supports it

cc_hotpatch	:= -mhotpatch=0,3

#define __smp_mb__before_atomic()	barrier()

#define __smp_mb__after_atomic()	barrier()

/**

 * array_index_mask_nospec - generate a mask for array_idx() that is

 * ~0UL when the bounds check succeeds and 0 otherwise

 * @index: array element index

 * @size: number of elements in array

 */

#define array_index_mask_nospec array_index_mask_nospec

static inline unsigned long array_index_mask_nospec(unsigned long index,

						    unsigned long size)

{

	unsigned long mask;

	if (__builtin_constant_p(size) && size > 0) {

		asm("	clgr	%2,%1\n"

		    "	slbgr	%0,%0\n"

		    :"=d" (mask) : "d" (size-1), "d" (index) :"cc");

		return mask;

	}

	asm("	clgr	%1,%2\n"

	    "	slbgr	%0,%0\n"

	    :"=d" (mask) : "d" (size), "d" (index) :"cc");

	return ~mask;

}

#include <asm-generic/barrier.h>

#endif /* __ASM_BARRIER_H */

#include <linux/types.h>

#include <linux/device.h>

#include <linux/blkdev.h>

#include <linux/blk_types.h>

struct arqb {

	u64 data;