[v3,4/9] xen: Use correctly the Xen memory terminologies

Based on include/xen/mm.h [1], Linux is mistakenly using MFN when GFN
is meant, I suspect this is because the first support for Xen was for
PV. This resulted in some misimplementation of helpers on ARM and
confused developers about the expected behavior.

For instance, with pfn_to_mfn, we expect to get an MFN based on the name.
Although, if we look at the implementation on x86, it's returning a GFN.

For clarity and avoid new confusion, replace any reference to mfn with
gfn in any helpers used by PV drivers. The x86 code will still keep some
reference of pfn_to_mfn but exclusively for PV (a BUG_ON has been added
to ensure this). No changes as been made in the hypercall field, even
though they may be invalid, in order to keep the same as the defintion
in xen repo.

Note that page_to_mfn has been renamed to xen_page_to_gfn to avoid a
name to close to the KVM function gfn_to_page.

Take also the opportunity to simplify simple construction such
as pfn_to_mfn(page_to_pfn(page)) into xen_page_to_gfn. More complex clean up
will come in follow-up patches.

[1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commitdiff;h=e758ed14f390342513405dd766e874934573e6cb

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

---
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: "James E.J. Bottomley" <JBottomley@odin.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: linux-input@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: linux-scsi@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-fbdev@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org

    Note that I've re-introduced in v2 mfn_to_pfn & co only for x86 PV code.
    The helpers contain a BUG_ON to ensure that it's never called for
    auto-translated guests. I did as best as my can to determine whether
    mfn or gfn helpers should be used. Although, I haven't tried to boot
    it.

    It may be possible to do further cleanup in the mmu.c where I found
    some check to auto-translated. I'm not sure why given that the pvmmu
    callback are only used for non-auto translated guest.

    Changes in v3:
        - Add Stefano's reviewed-by (except for the x86 bits)
        - Add Wei (netback) and Dmitry's (input) acked-by
        - Keep the VIRT <-> MACHINE macro in the same order as before
        in arch/x86/include/asm/xen/page.h
        - Rename page_to_gfn to xen_page_to_gfn to avoid confusion with
        the KVM function gfn_to_page.
        - Typoes in the commit title

    Changes in v2:
        - Give directly the URL to the commit rather than the commit ID
        - xenstored_local_init: keep the cast to void *
        - Typoes
        - Keep pfn_to_mfn for x86 and PV-only. The *mfn* helpers are
        used in arch/x86/xen for enlighten.c, mmu.c, p2m.c, setup.c,
        smp.c and mm.c
---
 arch/arm/include/asm/xen/page.h         | 13 +++++++------
 arch/x86/include/asm/xen/page.h         | 31 +++++++++++++++++++++++++------
 arch/x86/xen/smp.c                      |  2 +-
 drivers/block/xen-blkfront.c            |  6 +++---
 drivers/input/misc/xen-kbdfront.c       |  4 ++--
 drivers/net/xen-netback/netback.c       |  4 ++--
 drivers/net/xen-netfront.c              | 12 +++++++-----
 drivers/scsi/xen-scsifront.c            | 10 +++++-----
 drivers/tty/hvc/hvc_xen.c               |  5 +++--
 drivers/video/fbdev/xen-fbfront.c       |  4 ++--
 drivers/xen/balloon.c                   |  2 +-
 drivers/xen/events/events_base.c        |  2 +-
 drivers/xen/events/events_fifo.c        |  4 ++--
 drivers/xen/gntalloc.c                  |  3 ++-
 drivers/xen/manage.c                    |  2 +-
 drivers/xen/tmem.c                      |  4 ++--
 drivers/xen/xenbus/xenbus_client.c      |  2 +-
 drivers/xen/xenbus/xenbus_dev_backend.c |  2 +-
 drivers/xen/xenbus/xenbus_probe.c       |  8 +++-----
 include/xen/page.h                      |  4 ++--
 20 files changed, 73 insertions(+), 51 deletions(-)

[v3,4/9] xen: Use correctly the Xen memory terminologies

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