Signed-off-by: Bard Liao <bardliao@realtek.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

We need to make sure that the control's cached value is initialized to the same
value as the control's widget->on_val. Otherwise updates might be lost.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>

The current calls to dapm_mark_dirty() in snd_soc_dapm_add_path() are on a path
that is only reached if the sink widget is either a mixer or a mux. Move the
calls further up so they are called for all widget types.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>

Ensure that the recently added path kcontrol list is initialised otherwise
we may crash trying to delete routes that don't have kcontrols.
Signed-off-by: Mark Brown <broonie@linaro.org>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>

Attempting to create the route as part of adding a mux control causes us
to attempt to add the same route twice since we loop over all sources
for the mux after creating the control. Instead do the addition in the
callers.
Signed-off-by: Mark Brown <broonie@linaro.org>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>

Linux 3.11-rc5

Pull SCSI fixes from James Bottomley:
 "This is three bug fixes: An fnic warning caused by sleeping under a
  lock, a major regression with our updated WRITE SAME/UNMAP logic which
  caused tons of USB devices (and one RAID card) to cease to function
  and a megaraid_sas firmware initialisation problem which causes kdump
  failures"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  [SCSI] Don't attempt to send extended INQUIRY command if skip_vpd_pages is set
  [SCSI] fnic: BUG: sleeping function called from invalid context during probe
  [SCSI] megaraid_sas: megaraid_sas driver init fails in kdump kernel

Pull powerpc fixes from Ben Herrenschmidt:
 "This includes small series from Michael Neuling to fix a couple of
  nasty remaining problems with the new Power8 support, also targeted at
  stable 3.10, without which some new userspace accessible registers
  aren't properly context switched, and in some case, can be clobbered
  by the user of transactional memory.

  Along with that, a few slightly more minor things, such as a missing
  Kconfig option to enable handling of denorm exceptions when not
  running under a hypervisor (or userspace will randomly crash when
  hitting denorms with the vector unit), some nasty bugs in the new
  pstore oops code, and other simple bug fixes worth having in now.

  Note: I picked up the two powerpc KVM fixes as Alex Graf asked me to
  handle KVM bits while he is on vacation.  However I'll let him decide
  whether they should go to -stable or not when he is back"

* 'merge' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc:
  powerpc/tm: Fix context switching TAR, PPR and DSCR SPRs
  powerpc: Save the TAR register earlier
  powerpc: Fix context switch DSCR on POWER8
  powerpc: Rework setting up H/FSCR bit definitions
  powerpc: Fix hypervisor facility unavaliable vector number
  powerpc/kvm/book3s_pr: Return appropriate error when allocation fails
  powerpc/kvm: Add signed type cast for comparation
  powerpc/eeh: Add missing procfs entry for PowerNV
  powerpc/pseries: Add backward compatibilty to read old kernel oops-log
  powerpc/pseries: Fix buffer overflow when reading from pstore
  powerpc: On POWERNV enable PPC_DENORMALISATION by default

Pull s390 kvm fixes from Paolo Bonzini:
 "Two fixes for s390"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: s390: fix pfmf non-quiescing control handling
  KVM: s390: move kvm_guest_enter,exit closer to sie

Pull i2c fixes from Wolfram Sang:
 "Some driver bugfixes for the I2C subsystem"

* 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
  i2c: mv64xxx: Document the newly introduced allwinner compatible
  i2c: Fix Kontron PLD prescaler calculation
  i2c: i2c-mxs: Use DMA mode even for small transfers

Pull btrfs fixes from Chris Mason:
 "These are assorted fixes, mostly from Josef nailing down xfstests
  runs.  Zach also has a long standing fix for problems with readdir
  wrapping f_pos (or ctx->pos)

  These patches were spread out over different bases, so I rebased
  things on top of rc4 and retested overnight"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
  btrfs: don't loop on large offsets in readdir
  Btrfs: check to see if root_list is empty before adding it to dead roots
  Btrfs: release both paths before logging dir/changed extents
  Btrfs: allow splitting of hole em's when dropping extent cache
  Btrfs: make sure the backref walker catches all refs to our extent
  Btrfs: fix backref walking when we hit a compressed extent
  Btrfs: do not offset physical if we're compressed
  Btrfs: fix extent buffer leak after backref walking
  Btrfs: fix a bug of snapshot-aware defrag to make it work on partial extents
  btrfs: fix file truncation if FALLOC_FL_KEEP_SIZE is specified

Pull NFS client bugfixes from Trond Myklebust:

 - Stable patch for lockd to fix Oopses due to inappropriate calls to
   utsname()->nodename

 - Stable patches for sunrpc to fix Oopses on shutdown when using
   AF_LOCAL sockets with rpcbind

 - Fix memory leak and error checking issues in nfs4_proc_lookup_mountpoint

 - Fix a regression with the sync mount option failing to work for nfs4
   mounts

 - Fix a writeback performance issue when doing cache invalidation

 - Remove an incorrect call to nfs_setsecurity in nfs_fhget

* tag 'nfs-for-3.11-4' of git://git.linux-nfs.org/projects/trondmy/linux-nfs:
  NFSv4: Fix up nfs4_proc_lookup_mountpoint
  NFS: Remove unnecessary call to nfs_setsecurity in nfs_fhget()
  NFSv4: Fix the sync mount option for nfs4 mounts
  NFS: Fix writeback performance issue on cache invalidation
  SUNRPC: If the rpcbind channel is disconnected, fail the call to unregister
  SUNRPC: Don't auto-disconnect from the local rpcbind socket
  LOCKD: Don't call utsname()->nodename from nlmclnt_setlockargs

Pull nfsd fixes from Bruce Fields:
 "Some fixes for a 4.1 feature that in retrospect probably should have
  waited for 3.12....  But it appears to be working now"

* 'for-3.11' of git://linux-nfs.org/~bfields/linux:
  nfsd: Fix SP4_MACH_CRED negotiation in EXCHANGE_ID
  nfsd4: Fix MACH_CRED NULL dereference

Pull sound fixes from Takashi Iwai:
 "A couple of USB-audio fixes that should also go to stable kernels"

* tag 'sound-3.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound:
  ALSA: usb-audio: do not trust too-big wMaxPacketSize values
  ALSA: 6fire: fix DMA issues with URB transfer_buffer usage

Pull staging driver fixes from Greg KH:
 "Here are 3 small fixes for staging/IIO drivers for 3.11-rc5.  Nothing
  huge, two IIO driver fixes, and a zcache fix.  All of these have been
  in linux-next for a while"

* tag 'staging-3.11-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging:
  staging: zcache: fix "zcache=" kernel parameter
  iio: ti_am335x_adc: Fix wrong samples received on 1st read
  iio:trigger: Fix use_count race condition

Pull USB fixes from Greg KH:
 "Here are 3 small USB fixes for 3.11-rc5.

  One is a fix that the ChromeOS developers ran into on some Intel
  hardware, one is a build fix, and the last is a MAINTAINERS update to
  help people figure out where to send USB network driver patches.

  All of these have been in linux-next for a while"

* tag 'usb-3.11-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
  MAINTAINERS: Add separate section for USB NETWORKING DRIVERS
  usb: xhci: add missing dma-mapping.h includes
  usb: core: don't try to reset_device() a port that got just disconnected

When btrfs readdir() hits the last entry it sets the readdir offset to a
huge value to stop buggy apps from breaking when the same name is
returned by readdir() with concurrent rename()s.

But unconditionally setting the offset to INT_MAX causes readdir() to
loop returning any entries with offsets past INT_MAX.  It only takes a
few hours of constant file creation and removal to create entries past
INT_MAX.

So let's set the huge offset to LLONG_MAX if the last entry has already
overflowed 32bit loff_t.   Without large offsets behaviour is identical.
With large offsets 64bit apps will work and 32bit apps will be no more
broken than they currently are if they see large offsets.
Signed-off-by: Zach Brown <zab@redhat.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

A user reported a panic when running with autodefrag and deleting snapshots.
This is because we could end up trying to add the root to the dead roots list
twice.  To fix this check to see if we are empty before adding ourselves to the
dead roots list.  Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

The ceph guys tripped over this bug where we were still holding onto the
original path that we used to copy the inode with when logging.  This is based
on Chris's fix which was reported to fix the problem.  We need to drop the paths
in two cases anyway so just move the drop up so that we don't have duplicate
code.  Thanks,

Cc: stable@vger.kernel.org
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

I noticed while running multi-threaded fsync tests that sometimes fsck would
complain about an improper gap.  This happens because we fail to add a hole
extent to the file, which was happening when we'd split a hole EM because
btrfs_drop_extent_cache was just discarding the whole em instead of splitting
it.  So this patch fixes this by allowing us to split a hole em properly, which
means that added holes actually get logged properly and we no longer see this
fsck error.  Thankfully we're tolerant of these sort of problems so a user would
not see any adverse effects of this bug, other than fsck complaining.  Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

Because we don't mess with the offset into the extent for compressed we will
properly find both extents for this case

[extent a][extent b][rest of extent a]

but because we already added a ref for the front half we won't add the inode
information for the second half.  This causes us to leak that memory and not
print out the other offset when we do logical-resolve.  So fix this by calling
ulist_add_merge and then add our eie to the existing entry if there is one.
With this patch we get both offsets out of logical-resolve.  With this and the
other 2 patches I've sent we now pass btrfs/276 on my vm with compress-force=lzo
set.  Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

If you do btrfs inspect-internal logical-resolve on a compressed extent that has
been partly overwritten it won't find anything.  This is because we try and
match the extent offset we've searched for based on the extent offset in the
data extent entry.  However this doesn't work for compressed extents because the
offsets are for the uncompressed size, not the compressed size.  So instead only
do this check if we are not compressed, that way we can get an actual entry for
the physical offset rather than nothing for compressed.  Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

xfstest btrfs/276 was freaking out on slower boxes partly because fiemap was
offsetting the physical based on the extent offset.  This is perfectly fine with
uncompressed extents, however the extent offset is into the uncompressed area,
not the compressed.  So we can return a physical value that isn't at all within
the area we have allocated on disk.  Fix this by returning the start of the
extent if it is compressed no matter what the offset.  Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

commit 47fb091f(Btrfs: fix unlock after free on rewinded tree blocks)
takes an extra increment on the reference of allocated dummy extent buffer, so now we
cannot free this dummy one, and end up with extent buffer leak.
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

For partial extents, snapshot-aware defrag does not work as expected,
since
a) we use the wrong logical offset to search for parents, which should be
   disk_bytenr + extent_offset, not just disk_bytenr,
b) 'offset' returned by the backref walking just refers to key.offset, not
   the 'offset' stored in btrfs_extent_data_ref which is
   (key.offset - extent_offset).

The reproducer:
$ mkfs.btrfs sda
$ mount sda /mnt
$ btrfs sub create /mnt/sub
$ for i in `seq 5 -1 1`; do dd if=/dev/zero of=/mnt/sub/foo bs=5k count=1 seek=$i conv=notrunc oflag=sync; done
$ btrfs sub snap /mnt/sub /mnt/snap1
$ btrfs sub snap /mnt/sub /mnt/snap2
$ sync; btrfs filesystem defrag /mnt/sub/foo;
$ umount /mnt
$ btrfs-debug-tree sda (Here we can check whether the defrag operation is snapshot-awared.

This addresses the above two problems.
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

Create a small file and fallocate it to a big size with
FALLOC_FL_KEEP_SIZE option, then truncate it back to the
small size again, the disk free space is not changed back
in this case. i.e,

total 4
-rw-r--r-- 1 root root 512 Jun 28 11:35 test

Filesystem      Size  Used Avail Use% Mounted on
....
/dev/sdb1       8.0G   56K  7.2G   1% /mnt

-rw-r--r-- 1 root root 512 Jun 28 11:35 /mnt/test

Filesystem      Size  Used Avail Use% Mounted on
....
/dev/sdb1       8.0G  5.1G  2.2G  70% /mnt

Filesystem      Size  Used Avail Use% Mounted on
....
/dev/sdb1       8.0G  5.1G  2.2G  70% /mnt

With this fix, the truncated up space is back as:
Filesystem      Size  Used Avail Use% Mounted on
....
/dev/sdb1       8.0G   56K  7.2G   1% /mnt
Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

Pull ACPI and power management fixes from Rafael Wysocki:

 - ACPI-based memory hotplug stopped working after a recent change,
   because it's not possible to associate sufficiently many "physical"
   devices with one ACPI device object due to an artificial limit.  Fix
   from Rafael J Wysocki removes that limit and makes memory hotplug
   work again.

 - A change made in 3.9 uncovered a bug in the ACPI processor driver
   preventing NUMA nodes from being put offline due to an ordering
   issue.  Fix from Yasuaki Ishimatsu changes the ordering to make
   things work again.

 - One of the recent ACPI video commits (that hasn't been reverted so
   far) uncovered a bug in the code handling quirky BIOSes that caused
   some Asus machines to boot with backlight completely off which made
   it quite difficult to use them afterward.  Fix from Felipe Contreras
   improves the quirk to cover this particular case correctly.

 - A cpufreq user space interface change made in 3.10 inadvertently
   renamed the ignore_nice_load sysfs attribute to ignore_nice which
   resulted in some confusion.  Fix from Viresh Kumar changes the name
   back to ignore_nice_load.

 - An initialization ordering change made in 3.9 broke cpufreq on
   loongson2 boards.  Fix from Aaro Koskinen restores the correct
   initialization ordering there.

 - Fix breakage resulting from a mistake made in 3.9 and causing the
   detection of some graphics adapters (that were detected correctly
   before) to fail.  There are two objects representing the same PCIe
   port in the affected systems' ACPI tables and both appear as
   "enabled" and we are expected to guess which one to use.  We used to
   choose the right one before by pure luck, but when we tried to
   address another similar corner case, the luck went away.  This time
   we try to make our guessing a bit more educated which is reported to
   work on those systems.

 - The /proc/acpi/wakeup interface code is missing some locking which
   may lead to breakage if that file is written or read during hotplug
   of wakeup devices.  That should be rare but still possible, so it's
   better to start using the appropriate locking there.

* tag 'pm+acpi-3.11-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  ACPI: Try harder to resolve _ADR collisions for bridges
  cpufreq: rename ignore_nice as ignore_nice_load
  cpufreq: loongson2: fix regression related to clock management
  ACPI / processor: move try_offline_node() after acpi_unmap_lsapic()
  ACPI: Drop physical_node_id_bitmap from struct acpi_device
  ACPI / PM: Walk physical_node_list under physical_node_lock
  ACPI / video: improve quirk check in acpi_video_bqc_quirk()

Pull hwmon fix from Guenter Roeck:
 "Fix bug in adt7470 driver which causes it to fail writing fan speed
  limits"

* tag 'hwmon-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging:
  hwmon: (adt7470) Fix incorrect return code check

Pull media fixes from Mauro Carvalho Chehab:
 "Some driver fixes (em28xx, coda, usbtv, s5p, hdpvr and ml86v7667) and
  a fix for media DocBook"

* 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media:
  [media] em28xx: fix assignment of the eeprom data
  [media] hdpvr: fix iteration over uninitialized lists in hdpvr_probe()
  [media] usbtv: fix dependency
  [media] usbtv: Throw corrupted frames away
  [media] usbtv: Fix deinterlacing
  [media] v4l2: added missing mutex.h include to v4l2-ctrls.h
  [media] DocBook: upgrade media_api DocBook version to 4.2
  [media] ml86v7667: fix compile warning: 'ret' set but not used
  [media] s5p-g2d: Fix registration failure
  [media] media: coda: Fix DT driver data pointer for i.MX27
  [media] s5p-mfc: Fix input/output format reporting

Pull HID fix from Jiri Kosina:
 "Revert of a patch which breaks enumeration workaround in
  hid-logitech-dj"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid:
  Revert "HID: hid-logitech-dj: querying_devices was never set"

Pull fbdev fixes from Tomi Valkeinen:
 - omapdss: compilation fix and DVI fix for PandaBoard
 - mxsfb: fix colors when using 18bit LCD bus

* tag 'fbdev-fixes-3.11-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tomba/linux:
  ARM: OMAP: dss-common: fix Panda's DVI DDC channel
  video: mxsfb: fix color settings for 18bit data bus and 32bpp
  OMAPDSS: analog-tv-connector: compile fix

Pull drm fixes from Dave Airlie:
 "Mostly radeon, more fixes for dynamic power management which is is off
  by default for this release anyways, but there are a large number of
  testers, so I'd like to keep merging the fixes.

  Otherwise, radeon UVD fixes affecting suspend/resume regressions, i915
  regression fixes, one for your mac mini, ast, mgag200, cirrus ttm fix
  and one regression fix in the core"

* 'drm-fixes' of git://people.freedesktop.org/~airlied/linux: (25 commits)
  drm: Don't pass negative delta to ktime_sub_ns()
  drm/radeon: make missing smc ucode non-fatal
  drm/radeon/dpm: require rlc for dpm
  drm/radeon/cik: use a mutex to properly lock srbm instanced registers
  drm/radeon: remove unnecessary unpin
  drm/radeon: add more UVD CS checking
  drm/radeon: stop sending invalid UVD destroy msg
  drm/radeon: only save UVD bo when we have open handles
  drm/radeon: always program the MC on startup
  drm/radeon: fix audio dto calculation on DCE3+ (v3)
  drm/radeon/dpm: disable sclk ss on rv6xx
  drm/radeon: fix halting UVD
  drm/radeon/dpm: adjust power state properly for UVD on SI
  drm/radeon/dpm: fix spread spectrum setup (v2)
  drm/radeon/dpm: adjust thermal protection requirements
  drm/radeon: select audio dto based on encoder id for DCE3
  drm/radeon: properly handle pm on gpu reset
  drm/i915: do not disable backlight on vgaswitcheroo switch off
  drm/i915: Don't call encoder's get_config unless encoder is active
  drm/i915: avoid brightness overflow when doing scale
  ...

device_close()->recalc_sigpending() is not needed, sigprocmask() takes
care of TIF_SIGPENDING correctly.

And without ->siglock it is racy and wrong, it can wrongly clear
TIF_SIGPENDING and miss a signal.

But even with this patch device_close() is still buggy:

  1. sigprocmask() should not be used, we have set_task_blocked(),
     but this is minor.

  2. We should never block SIGKILL or SIGSTOP, and this is what
     the code tries to do.

  3. This can't protect against SIGKILL or SIGSTOP anyway. Another
     thread can do signal_wake_up(), say, do_signal_stop() or
     complete_signal() or debugger.

  4. sigprocmask(SIG_BLOCK, allsigs) doesn't necessarily clears
     TIF_SIGPENDING, say, freezing() or ->jobctl.

  5. device_write() looks equally wrong by the same reason.

Looks like, this tries to protect some wait_event_interruptible() logic
from signals, it should be turned into uninterruptible wait.  Or we need
to implement something like signals_stop/start for such a use-case.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This reverts commit 407a2c2a.

Explanation provided by Benjamin Tissoires:

Commit "HID: hid-logitech-dj, querying_devices was never set" activate
a flag which guarantees that we do not ask the receiver for too many
enumeration. When the flag is set, each following enumeration call is
discarded (the usb request is not forwarded to the receiver). The flag
is then released when the driver receive a pairing information event,
which normally follows the enumeration request.
However, the USB3 bug makes the driver think the enumeration request
has been forwarded to the receiver. However, it is actually not the
case because the USB stack returns -EPIPE. So, when a new unknown
device appears, the workaround consisting in asking for a new
enumeration is not working anymore: this new enumeration is discarded
because of the flag, which is never reset.

A solution could be to trigger a timeout before releasing it, but for
now, let's just revert the patch.
Reported-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Tested-by: Sune Mølgaard <sune@molgaard.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

If a transaction is rolled back, the Target Address Register (TAR), Processor
Priority Register (PPR) and Data Stream Control Register (DSCR) should be
restored to the checkpointed values before the transaction began.  Any changes
to these SPRs inside the transaction should not be visible in the abort
handler.

Currently Linux doesn't save or restore the checkpointed TAR, PPR or DSCR.  If
we preempt a processes inside a transaction which has modified any of these, on
process restore, that same transaction may be aborted we but we won't see the
checkpointed versions of these SPRs.

This adds checkpointed versions of these SPRs to the thread_struct and adds the
save/restore of these three SPRs to the treclaim/trechkpt code.

Without this if any of these SPRs are modified during a transaction, users may
incorrectly see a speculated SPR value even if the transaction is aborted.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Cc: <stable@vger.kernel.org> [v3.10]
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

This moves us to save the Target Address Register (TAR) a earlier in
__switch_to.  It introduces a new function save_tar() to do this.

We need to save the TAR earlier as we will overwrite it in the transactional
memory reclaim/recheckpoint path.  We are going to do this in a subsequent
patch which will fix saving the TAR register when it's modified inside a
transaction.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Cc: <stable@vger.kernel.org> [v3.10]
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

POWER8 allows the DSCR to be accessed directly from userspace via a new SPR
number 0x3 (Rather than 0x11.  DSCR SPR number 0x11 is still used on POWER8 but
like POWER7, is only accessible in HV and OS modes).  Currently, we allow this
by setting H/FSCR DSCR bit on boot.

Unfortunately this doesn't work, as the kernel needs to see the DSCR change so
that it knows to no longer restore the system wide version of DSCR on context
switch (ie. to set thread.dscr_inherit).

This clears the H/FSCR DSCR bit initially.  If a process then accesses the DSCR
(via SPR 0x3), it'll trap into the kernel where we set thread.dscr_inherit in
facility_unavailable_exception().

We also change _switch() so that we set or clear the H/FSCR DSCR bit based on
the thread.dscr_inherit.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Cc: <stable@vger.kernel.org> [v3.10]
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>