virtio: memory accessors for endian-ambivalent targets

This is the virtio-access.h header file taken from Rusty's "endian-ambivalent
targets using legacy virtio" patch. It introduces helpers that should be used
when accessing vring data or by drivers for data that contains headers.
The virtio config space is also target endian, but the current code already
handles that with the virtio_is_big_endian() helper. There is no obvious
benefit at using the virtio accessors in this case.

Now we have two distinct paths: a fast inline one for fixed endian targets,
and a slow out-of-line one for targets that define the new TARGET_IS_BIENDIAN
macro.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
[ relicensed virtio-access.h to GPLv2+ on Rusty's request,
  pass &address_space_memory to physical memory accessors,
  per-device endianness,
  virtio tswap16 and tswap64 helpers,
  Greg Kurz <gkurz@linux.vnet.ibm.com> ]
Cc: Cédric Le Goater <clg@fr.ibm.com>
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
virtio: allow byte swapping for vring

Quoting original text from Rusty: "This is based on a simpler patch by Anthony
Liguouri".

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
[ add VirtIODevice * argument to most helpers,
  Greg Kurz <gkurz@linux.vnet.ibm.com> ]
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Reviewed-by: Thomas Huth <thuth@linux.vnet.ibm.com>
virtio-net: use virtio wrappers to access headers

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
[ pass VirtIODevice * to memory accessors,
  TCP checksums fix by Cédric Le Goater,
  Greg Kurz <gkurz@linux.vnet.ibm.com> ]
Cc: Cédric Le Goater <clg@fr.ibm.com>
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
virtio-balloon: use virtio wrappers to access page frame numbers

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
[ pass VirtIODevice * to memory accessors,
  Greg Kurz <gkurz@linux.vnet.ibm.com> ]
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
virtio-blk: use virtio wrappers to access headers

Note that st*_raw and ld*_raw are effectively replaced by st*_p and ld*_p.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
[ pass VirtIODevice * to memory accessors,
  Greg Kurz <gkurz@linux.vnet.ibm.com> ]
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
virtio-scsi: use virtio wrappers to access headers

Note that st*_raw and ld*_raw are effectively replaced by st*_p and ld*_p.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
[ pass VirtIODevice * to memory accessors,
  fix missing tswap32 in virtio_scsi_push_event() by Cédric Le Goater,
  Greg Kurz <gkurz@linux.vnet.ibm.com> ]
Cc: Cédric Le Goater <clg@fr.ibm.com>
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
virtio-serial-bus: use virtio wrappers to access headers

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
[ pass VirtIODevice * to memory accessors,
  Greg Kurz <gkurz@linux.vnet.ibm.com> ]
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
virtio-9p: use virtio wrappers to access headers

Note that st*_raw and ld*_raw are effectively replaced by st*_p and ld*_p.

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
target-ppc: ppc64 can be either endian

POWER7, POWER7+ and POWER8 families use the ILE bit of the LPCR
special purpose register to decide the endianness to use when
entering interrupt handlers. When running a linux guest, this
provides a hint on the endianness used by the kernel. From a
qemu point of view, the information is needed for legacy virtio
support and possibly crash dump support as well.

Suggested-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
target-ppc: enable virtio endian ambivalent support

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>