The Ippo-q8h is a tablet circuit board commonly found in cheap Android
tablets with A23 SoCs. There are at least 2 versions of the board, with
different peripherals, such as WiFi chips.

Common features among these tablets include 512 MB DRAM, NAND, MMC, LCD,
capacitive touchscreen, accelerometer, 1 or 2 camera sensors, USB OTG,
microphone and speaker.

v5 of these board designs has a ESP8089 WiFi chip (not supported)
connected to mmc1. This patch adds very basic support.
Signed-off-by: NChen-Yu Tsai <wens@csie.org>
Signed-off-by: NMaxime Ripard <maxime.ripard@free-electrons.com>

The Allwinner A23 is a tablet oriented SoC with 2 Cortex-A7 cores
and a Mali-400MP2 GPU.
Signed-off-by: NChen-Yu Tsai <wens@csie.org>
Signed-off-by: NMaxime Ripard <maxime.ripard@free-electrons.com>

This patch adds records for two IR controllers on A20
Signed-off-by: NAlexander Bersenev <bay@hackerdom.ru>
Signed-off-by: NAlexsey Shestacov <wingrime@linux-sunxi.org>
Signed-off-by: NMaxime Ripard <maxime.ripard@free-electrons.com>

This patch enables two IR devices in dts:
- One IR device physically found on Cubieboard 2
- One IR device physically found on Cubietruck
Signed-off-by: NAlexander Bersenev <bay@hackerdom.ru>
Signed-off-by: NAlexsey Shestacov <wingrime@linux-sunxi.org>
Signed-off-by: NMaxime Ripard <maxime.ripard@free-electrons.com>

This patch adds pins for two IR controllers on A20
Signed-off-by: NAlexander Bersenev <bay@hackerdom.ru>
Signed-off-by: NAlexsey Shestacov <wingrime@linux-sunxi.org>
Signed-off-by: NMaxime Ripard <maxime.ripard@free-electrons.com>

"make vdso_install" installs unstripped versions of the vdso objects
for the benefit of the debugger.  This was broken by checkin:

6f121e54 x86, vdso: Reimplement vdso.so preparation in build-time C

The filenames are different now, so update the Makefile to cope.

This still installs the 64-bit vdso as vdso64.so.  We believe this
will be okay, as the only known user is a patched gdb which is known
to use build-ids, but if it turns out to be a problem we may have to
add a link.

Inspired by a patch from Sam Ravnborg.
Acked-by: NSam Ravnborg <sam@ravnborg.org>
Reported-by: NJosh Boyer <jwboyer@fedoraproject.org>
Tested-by: NJosh Boyer <jwboyer@fedoraproject.org>
Signed-off-by: NAndy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/b10299edd8ba98d17e07dafcd895b8ecf4d99eff.1402586707.git.luto@amacapital.netSigned-off-by: NH. Peter Anvin <hpa@zytor.com>

The Go runtime has a buggy vDSO parser that currently segfaults.
This writes an empty SHT_DYNSYM entry that causes Go's runtime to
malfunction by thinking that the vDSO is empty rather than
malfunctioning by running off the end and segfaulting.

This affects x86-64 only as far as we know, so we do not need this for
the i386 and x32 vdsos.
Signed-off-by: NAndy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/d10618176c4bd39b457a5e85c497295c90cab1bc.1402620737.git.luto@amacapital.netSigned-off-by: NH. Peter Anvin <hpa@zytor.com>

Add PUT_LE() by analogy with GET_LE() to write littleendian values in
addition to reading them.
Signed-off-by: NAndy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/3d9b27e92745b27b6fda1b9a98f70dc9c1246c7a.1402620737.git.luto@amacapital.netSigned-off-by: NH. Peter Anvin <hpa@zytor.com>

These defconfigs contain the CONFIG_M25P80 symbol, which is now
dependent on the MTD_SPI_NOR symbol. Add CONFIG_MTD_SPI_NOR to the
relevant defconfigs.

At the same time, drop the now-nonexistent CONFIG_MTD_CHAR symbol.
Signed-off-by: NBrian Norris <computersforpeace@gmail.com>
Cc: Steven Miao <realmz6@gmail.com>
Cc: adi-buildroot-devel@lists.sourceforge.net
Cc: linux-kernel@vger.kernel.org

The rule to create the final images uses a zImage.% pattern.
Unfortunately, this also matches the names of the zImage.*.lds linker
scripts, which appear as a dependency of the final images. This somehow
worked when $(srctree) used to be an absolute path, but now the pattern
matches too much. List only the images from $(image-y) as the target of
the rule, to avoid the circular dependency.
Reported-and-tested-by: NMike Qiu <qiudayu@linux.vnet.ibm.com>
Signed-off-by: NMichal Marek <mmarek@suse.cz>

Commit 2749a2f2 (powerpc/book3s: Fix machine check handling for
unhandled errors) introduced a few ABIv2 issues.

We can maintain ABIv1 and ABIv2 compatibility by branching to the
function rather than the dot symbol.

Fixes: 2749a2f2 ("powerpc/book3s: Fix machine check handling for unhandled errors")
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Currently we forward MCEs to guest which have been recovered by guest.
And for unhandled errors we do not deliver the MCE to guest. It looks like
with no support of FWNMI in qemu, guest just panics whenever we deliver the
recovered MCEs to guest. Also, the existig code used to return to host for
unhandled errors which was casuing guest to hang with soft lockups inside
guest and makes it difficult to recover guest instance.

This patch now forwards all fatal MCEs to guest causing guest to crash/panic.
And, for recovered errors we just go back to normal functioning of guest
instead of returning to host. This fixes soft lockup issues in guest.
This patch also fixes an issue where guest MCE events were not logged to
host console.
Signed-off-by: NMahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

We don't see MCE counter getting increased in /proc/interrupts which gives
false impression of no MCE occurred even when there were MCE events.
The machine check early handling was added for PowerKVM and we missed to
increment the MCE count in the early handler.

We also increment mce counters in the machine_check_exception call, but
in most cases where we handle the error hypervisor never reaches there
unless its fatal and we want to crash. Only during fatal situation we may
see double increment of mce count. We need to fix that. But for
now it always good to have some count increased instead of zero.
Signed-off-by: NMahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Currently machine check handler does not check for stack overflow for
nested machine check. If we hit another MCE while inside the machine check
handler repeatedly from same address then we get into risk of stack
overflow which can cause huge memory corruption. This patch limits the
nested MCE level to 4 and panic when we cross level 4.
Signed-off-by: NMahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Current code does not check for unhandled/unrecovered errors and return from
interrupt if it is recoverable exception which in-turn triggers same machine
check exception in a loop causing hypervisor to be unresponsive.

This patch fixes this situation and forces hypervisor to panic for
unhandled/unrecovered errors.

This patch also fixes another issue where unrecoverable_exception routine
was called in real mode in case of unrecoverable exception (MSR_RI = 0).
This causes another exception vector 0x300 (data access) during system crash
leading to confusion while debugging cause of the system crash.

Also turn ME bit off while going down, so that when another MCE is hit during
panic path, system will checkstop and hypervisor will get restarted cleanly
by SP.

With the above fixes we now throw correct console messages (see below) while
crashing the system in case of unhandled/unrecoverable machine checks.

--------------
Severe Machine check interrupt [[Not recovered]
  Initiator: CPU
  Error type: UE [Instruction fetch]
    Effective address: 0000000030002864
Oops: Machine check, sig: 7 [#1]
SMP NR_CPUS=2048 NUMA PowerNV
Modules linked in: bork(O) bridge stp llc kvm [last unloaded: bork]
CPU: 36 PID: 55162 Comm: bash Tainted: G           O 3.14.0mce #1
task: c000002d72d022d0 ti: c000000007ec0000 task.ti: c000002d72de4000
NIP: 0000000030002864 LR: 00000000300151a4 CTR: 000000003001518c
REGS: c000000007ec3d80 TRAP: 0200   Tainted: G           O  (3.14.0mce)
MSR: 9000000000041002 <SF,HV,ME,RI>  CR: 28222848  XER: 20000000
CFAR: 0000000030002838 DAR: d0000000004d0000 DSISR: 00000000 SOFTE: 1
GPR00: 000000003001512c 0000000031f92cb0 0000000030078af0 0000000030002864
GPR04: d0000000004d0000 0000000000000000 0000000030002864 ffffffffffffffc9
GPR08: 0000000000000024 0000000030008af0 000000000000002c c00000000150e728
GPR12: 9000000000041002 0000000031f90000 0000000010142550 0000000040000000
GPR16: 0000000010143cdc 0000000000000000 00000000101306fc 00000000101424dc
GPR20: 00000000101424e0 000000001013c6f0 0000000000000000 0000000000000000
GPR24: 0000000010143ce0 00000000100f6440 c000002d72de7e00 c000002d72860250
GPR28: c000002d72860240 c000002d72ac0038 0000000000000008 0000000000040000
NIP [0000000030002864] 0x30002864
LR [00000000300151a4] 0x300151a4
Call Trace:
Instruction dump:
XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
---[ end trace 7285f0beac1e29d3 ]---

Sending IPI to other CPUs
IPI complete
OPAL V3 detected !
--------------
Signed-off-by: NMahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

As Ben suggested, it's meaningful to dump PE's location code
for site engineers when hitting EEH errors. The patch introduces
function eeh_pe_loc_get() to retireve the location code from
dev-tree so that we can output it when hitting EEH errors.

If primary PE bus is root bus, the PHB's dev-node would be tried
prior to root port's dev-node. Otherwise, the upstream bridge's
dev-node of the primary PE bus will be check for the location code
directly.
Signed-off-by: NGavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The macro 'A' used in internal BPF interpreter:
 #define A regs[insn->a_reg]
was easily confused with the name of classic BPF register 'A', since
'A' would mean two different things depending on context.

This patch is trying to clean up the naming and clarify its usage in the
following way:

- A and X are names of two classic BPF registers

- BPF_REG_A denotes internal BPF register R0 used to map classic register A
  in internal BPF programs generated from classic

- BPF_REG_X denotes internal BPF register R7 used to map classic register X
  in internal BPF programs generated from classic

- internal BPF instruction format:
struct sock_filter_int {
        __u8    code;           /* opcode */
        __u8    dst_reg:4;      /* dest register */
        __u8    src_reg:4;      /* source register */
        __s16   off;            /* signed offset */
        __s32   imm;            /* signed immediate constant */
};

- BPF_X/BPF_K is 1 bit used to encode source operand of instruction
In classic:
  BPF_X - means use register X as source operand
  BPF_K - means use 32-bit immediate as source operand
In internal:
  BPF_X - means use 'src_reg' register as source operand
  BPF_K - means use 32-bit immediate as source operand
Suggested-by: NChema Gonzalez <chema@google.com>
Signed-off-by: NAlexei Starovoitov <ast@plumgrid.com>
Acked-by: NDaniel Borkmann <dborkman@redhat.com>
Acked-by: NChema Gonzalez <chema@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch enables POWER8 doorbell IPIs on powernv.

Since doorbells can only IPI within a core, we test to see when we can use
doorbells and if not we fall back to XICS.  This also enables hypervisor
doorbells to wakeup us up from nap/sleep via the LPCR PECEDH bit.

Based on tests by Anton, the best case IPI latency between two threads dropped
from 894ns to 512ns.
Signed-off-by: NMichael Neuling <mikey@neuling.org>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

On PowerNV platform, EEH errors are reported by IO accessors or poller
driven by interrupt. After the PE is isolated, we won't produce EEH
event for the PE. The current implementation has possibility of EEH
event lost in this way:

The interrupt handler queues one "special" event, which drives the poller.
EEH thread doesn't pick the special event yet. IO accessors kicks in, the
frozen PE is marked as "isolated" and EEH event is queued to the list.
EEH thread runs because of special event and purge all existing EEH events.
However, we never produce an other EEH event for the frozen PE. Eventually,
the PE is marked as "isolated" and we don't have EEH event to recover it.

The patch fixes the issue to keep EEH events for PEs that have been
marked as "isolated" with the help of additional "force" help to
eeh_remove_event().
Reported-by: NRolf Brudeseth <rolfb@us.ibm.com>
Signed-off-by: NGavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Commit b0d278b7 ("powerpc/perf_event: Reduce latency of calling
perf_event_do_pending") added a check for CONFIG_PMAC were a check for
CONFIG_PPC_PMAC was clearly intended.

Fixes: b0d278b7 ("powerpc/perf_event: Reduce latency of calling perf_event_do_pending")
Signed-off-by: NPaul Bolle <pebolle@tiscali.nl>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Commit cd64d169 ("powerpc: mtmsrd not defined") added a check for
CONFIG_PPC_CPU were a check for CONFIG_PPC_FPU was clearly intended.

Fixes: cd64d169 ("powerpc: mtmsrd not defined")
Signed-off-by: NPaul Bolle <pebolle@tiscali.nl>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Commit cb5b242c ("powerpc/eeh: Escalate error on non-existing PE")
escalates the frozen state on non-existing PE to fenced PHB. It
was to improve kdump reliability. After that, commit 361f2a2a
("powrpc/powernv: Reset PHB in kdump kernel") was introduced to
issue complete reset on all PHBs to increase the reliability of
kdump kernel.

Commit cb5b242c becomes unuseful and it would be reverted.
Signed-off-by: NGavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

When we have the corner case of frozen parent and child PE at the
same time, we have to handle the frozen parent PE prior to the
child. Without clearning the frozen state on parent PE, the child
PE can't be recovered successfully.

The patch searches the EEH PE hierarchy tree and returns the toppest
frozen PE to be handled. It ensures the frozen parent PE will be
handled prior to child PE.
Signed-off-by: NGavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Since commit cb523e09 ("powerpc/eeh: Avoid I/O access during PE
reset"), the PE is kept as frozen state on hardware level until
the PE reset is done completely. After that, we explicitly clear
the frozen state of the affected PE. However, there might have
frozen child PEs of the affected PE and we also need clear their
frozen state as well. Otherwise, the recovery is going to fail.
Signed-off-by: NGavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

We've already dropped the default pseries timeout to 10s, do
the same for powernv.
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

This makes sure format strings cannot leak into printk (the string has
already been correctly processed for format arguments).
Signed-off-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

In commit 330a1eb7 "Core EBB support for 64-bit book3s" I messed up
clear_task_ebb(). It clears some but not all of the task's Event Based
Branch (EBB) registers when we duplicate a task struct.

That allows a child task to observe the EBBHR & EBBRR of its parent,
which it should not be able to do.

Fix it by clearing EBBHR & EBBRR.
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
Cc: stable@vger.kernel.org [v3.11+]
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

memory_return_from_buffer returns a signed value, so ret should be
ssize_t.

Fixes the following issue reported by David Binderman:

  [linux-3.15/arch/powerpc/platforms/powernv/opal-msglog.c:65]: (style)
  Checking if unsigned variable 'ret' is less than zero.
  [linux-3.15/arch/powerpc/platforms/powernv/opal-msglog.c:82]: (style)
  Checking if unsigned variable 'ret' is less than zero.

  Local variable "ret" is of type size_t. This is always unsigned,
  so it is pointless to check if it is less than zero.

  https://bugzilla.kernel.org/show_bug.cgi?id=77551

Fixing this exposes a real bug for the case where the entire count
bytes is successfully read from the POS_WRAP case. The second
memory_read_from_buffer will return EINVAL, causing the entire read to
return EINVAL to userspace, despite the data being copied correctly. The
fix is to test for the case where the data has been read and return
early.
Signed-off-by: NJoel Stanley <joel@jms.id.au>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The SPUFS_CNTL_MAP_SIZE define is cut and pasted twice so we can delete
the second instance.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NJeremy Kerr <jk@ozlabs.org>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The FCC_GFMR_TTX define is cut and pasted twice so we can remove the
second instance.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

EEH information fetched from OPAL need fix before using in LE environment.
To be included in sparse's endian check, declare them as __beXX and
access them by accessors.

Cc: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: NGuo Chao <yan@linux.vnet.ibm.com>
Acked-by: NGavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Everyone can write to these files, which is not what we want.

Cc: stable@vger.kernel.org # 3.15
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Build throws following errors when CONFIG_SMP=n
arch/powerpc/platforms/powernv/subcore.c: In function ‘cpu_update_split_mode’:
arch/powerpc/platforms/powernv/subcore.c:274:15: error: ‘setup_max_cpus’ undeclared (first use in this function)
arch/powerpc/platforms/powernv/subcore.c:285:5: error: lvalue required as left operand of assignment

'setup_max_cpus' variable is relevant only on SMP, so there is no point
working around it for UP. Furthermore, subcore itself is relevant only
on SMP and hence the better solution is to exclude subcore.o and
subcore-asm.o for UP builds.
Signed-off-by: NShreyas B. Prabhu <shreyas@linux.vnet.ibm.com>
Reviewed-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Build throws following errors when CONFIG_SMP=n
arch/powerpc/platforms/powernv/setup.c: In function ‘pnv_kexec_wait_secondaries_down’:
arch/powerpc/platforms/powernv/setup.c:179:4: error: implicit declaration of function ‘get_hard_smp_processor_id’
    rc = opal_query_cpu_status(get_hard_smp_processor_id(i),

The usage of get_hard_smp_processor_id() needs the declaration from
<asm/smp.h>. The file setup.c includes <linux/sched.h>, which in-turn
includes <linux/smp.h>. However, <linux/smp.h> includes <asm/smp.h>
only on SMP configs and hence UP builds fail.

Fix this by directly including <asm/smp.h> in setup.c unconditionally.
Reported-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: NShreyas B. Prabhu <shreyas@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

OPAL will mark a CPU that is guarded as "bad" in the status property of the CPU
node.

Unfortunatley Linux doesn't check this property and will put the bad CPU in the
present map.  This has caused hangs on booting when we try to unsplit the core.

This patch checks the CPU is avaliable via this status property before putting
it in the present map.
Signed-off-by: NMichael Neuling <mikey@neuling.org>
Tested-by: NAnton Blanchard <anton@samba.org>
cc: stable@vger.kernel.org
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Correct the DSCR SPR becoming temporarily corrupted if a task is
context switched during a transaction.

The problem occurs while suspending the task and is caused by saving
the DSCR to thread.dscr after it has already been set to the CPU's
default value:

__switch_to() calls __switch_to_tm()
	which calls tm_reclaim_task()
	which calls tm_reclaim_thread()
	which calls tm_reclaim()
		where the DSCR is set to the CPU's default
__switch_to() calls _switch()
		where thread.dscr is set to the DSCR

When the task is resumed, it's transaction will be doomed (as usual)
and the DSCR SPR will be corrupted, although the checkpointed value
will be correct. Therefore the DSCR will be immediately corrected by
the transaction aborting, unless it has been suspended. In that case
the incorrect value can be seen by the task until it resumes the
transaction.

The fix is to treat the DSCR similarly to the TAR and save it early
in __switch_to().

A program exposing the problem is added to the kernel self tests as:
tools/testing/selftests/powerpc/tm/tm-resched-dscr.
Signed-off-by: NSam Bobroff <sam.bobroff@au1.ibm.com>
CC: <stable@vger.kernel.org> [v3.10+]
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

__attribute__ ((unused))

WSP is the last user of CONFIG_PPC_A2, so we remove that as well.

Although CONFIG_PPC_ICSWX still exists, it's no longer selectable for
any Book3E platform, so we can remove the code in mmu-book3e.h that
depended on it.
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The Kconfig symbol SERIAL_TEXT_DEBUG was removed from
arch/powerpc/Kconfig.debug in v2.6.22. (In v2.6.27 it was also removed
from arch/ppc/Kconfig.debug.) So the check for its macro has evaluated
to false for over five years now. Remove that check and the few lines
of code hidden behind it.
Signed-off-by: NPaul Bolle <pebolle@tiscali.nl>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The Vector Crypto category instructions are supported by current POWER8
chips, advertise them to userspace using a specific bit to properly
differentiate with chips of the same architecture level that might not
have them.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
CC: <stable@vger.kernel.org> [v3.10+]

One final use of the macros from <endian.h> which are not available on
older system.  In this case we had one sole case of *writing* a
littleendian number, but the number is SHN_UNDEF which is the constant
zero, so rather than dealing with the general case of littleendian
puts here, just document that the constant is zero and be done with
it.
Reported-and-Tested-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/20140610135051.c3c34165f73d67d218b62bd9@linux-foundation.org