We are currently maintaining:

  runnable_load(cfs_rq) = \Sum task_load(t)

For all running children t of cfs_rq.  While this can be naturally updated for
tasks in a runnable state (as they are scheduled); this does not account for
the load contributed by blocked task entities.

This can be solved by introducing a separate accounting for blocked load:

  blocked_load(cfs_rq) = \Sum runnable(b) * weight(b)

Obviously we do not want to iterate over all blocked entities to account for
their decay, we instead observe that:

  runnable_load(t) = \Sum p_i*y^i

and that to account for an additional idle period we only need to compute:

  y*runnable_load(t).

This means that we can compute all blocked entities at once by evaluating:

  blocked_load(cfs_rq)` = y * blocked_load(cfs_rq)

Finally we maintain a decay counter so that when a sleeping entity re-awakens
we can determine how much of its load should be removed from the blocked sum.
Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141506.585389902@google.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

For a given task t, we can compute its contribution to load as:

  task_load(t) = runnable_avg(t) * weight(t)

On a parenting cfs_rq we can then aggregate:

  runnable_load(cfs_rq) = \Sum task_load(t), for all runnable children t

Maintain this bottom up, with task entities adding their contributed load to
the parenting cfs_rq sum.  When a task entity's load changes we add the same
delta to the maintained sum.
Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141506.514678907@google.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

Since runqueues do not have a corresponding sched_entity we instead embed a
sched_avg structure directly.
Signed-off-by: Ben Segall <bsegall@google.com>
Reviewed-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141506.442637130@google.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

Instead of tracking averaging the load parented by a cfs_rq, we can track
entity load directly. With the load for a given cfs_rq then being the sum
of its children.

To do this we represent the historical contribution to runnable average
within each trailing 1024us of execution as the coefficients of a
geometric series.

We can express this for a given task t as:

  runnable_sum(t) = \Sum u_i * y^i, runnable_avg_period(t) = \Sum 1024 * y^i
  load(t) = weight_t * runnable_sum(t) / runnable_avg_period(t)

Where: u_i is the usage in the last i`th 1024us period (approximately 1ms)
~ms and y is chosen such that y^k = 1/2.  We currently choose k to be 32 which
roughly translates to about a sched period.
Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141506.372695337@google.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

Merge tag 'stable/for-linus-3.7-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen

Pull xen bug-fixes from Konrad Rzeszutek Wilk:
 - Fix mysterious SIGSEGV or SIGKILL in applications due to corrupting
   of the %eip when returning from a signal handler.
 - Fix various ARM compile issues after the merge fallout.
 - Continue on making more of the Xen generic code usable by ARM
   platform.
 - Fix SR-IOV passthrough to mirror multifunction PCI devices.
 - Fix various compile warnings.
 - Remove hypercalls that don't exist anymore.

* tag 'stable/for-linus-3.7-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen:
  xen: dbgp: Fix warning when CONFIG_PCI is not enabled.
  xen: arm: comment on why 64-bit xen_pfn_t is safe even on 32 bit
  xen: balloon: use correct type for frame_list
  xen/x86: don't corrupt %eip when returning from a signal handler
  xen: arm: make p2m operations NOPs
  xen: balloon: don't include e820.h
  xen: grant: use xen_pfn_t type for frame_list.
  xen: events: pirq_check_eoi_map is X86 specific
  xen: XENMEM_translate_gpfn_list was remove ages ago and is unused.
  xen: sysfs: fix build warning.
  xen: sysfs: include err.h for PTR_ERR etc
  xen: xenbus: quirk uses x86 specific cpuid
  xen PV passthru: assign SR-IOV virtual functions to separate virtual slots
  xen/xenbus: Fix compile warning.
  xen/x86: remove duplicated include from enlighten.c

... and fix the race in updating unaligned control ones
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull kvm fixes from Avi Kivity:
 "KVM updates for 3.7-rc2"

* tag 'kvm-3.7-2' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM guest: exit idleness when handling KVM_PV_REASON_PAGE_NOT_PRESENT
  KVM: apic: fix LDR calculation in x2apic mode
  KVM: MMU: fix release noslot pfn

Pull perf fixes from Ingo Molnar:
 "Most of these are uprobes race fixes from Oleg, and their preparatory
  cleanups.  (It's larger than what I'd normally send for an -rc kernel,
  but they looked significant enough to not delay them.)

  There's also an oprofile fix and an uncore PMU fix."

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (22 commits)
  perf/x86: Disable uncore on virtualized CPUs
  oprofile, x86: Fix wrapping bug in op_x86_get_ctrl()
  ring-buffer: Check for uninitialized cpu buffer before resizing
  uprobes: Fix the racy uprobe->flags manipulation
  uprobes: Fix prepare_uprobe() race with itself
  uprobes: Introduce prepare_uprobe()
  uprobes: Fix handle_swbp() vs unregister() + register() race
  uprobes: Do not delete uprobe if uprobe_unregister() fails
  uprobes: Don't return success if alloc_uprobe() fails
  uprobes/x86: Only rep+nop can be emulated correctly
  uprobes: Simplify is_swbp_at_addr(), remove stale comments
  uprobes: Kill set_orig_insn()->is_swbp_at_addr()
  uprobes: Introduce copy_opcode(), kill read_opcode()
  uprobes: Kill set_swbp()->is_swbp_at_addr()
  uprobes: Restrict valid_vma(false) to skip VM_SHARED vmas
  uprobes: Change valid_vma() to demand VM_MAYEXEC rather than VM_EXEC
  uprobes: Change write_opcode() to use FOLL_FORCE
  uprobes: Move clear_thread_flag(TIF_UPROBE) to uprobe_notify_resume()
  uprobes: Kill UTASK_BP_HIT state
  uprobes: Fix UPROBE_SKIP_SSTEP checks in handle_swbp()
  ...

Pull core kernel fixes from Ingo Molnar:
 "Two small fixes"

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Documentation: Reflect the new location of the NMI watchdog info
  nohz: Fix idle ticks in cpu summary line of /proc/stat

Pull s390 fixes from Martin Schwidefsky:
 "Among the usual minor bug fixes the more interesting patches are the
  perf counters for the latest machine, the missing select to enable
  transparent huge pages and a build fix for the UAPI rework."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390,uapi: do not use uapi/asm-generic/kvm_para.h
  s390/cache: fix data/instruction cache output
  s390: fix linker script for 31 bit builds
  s390/thp: select HAVE_ARCH_TRANSPARENT_HUGEPAGE
  s390/kdump: Use 64 bit mode for 0x10000 entry point
  perf_cpum_cf: Add support for counters available with IBM zEC12
  s390/css: stop stsch loop after cc 3
  s390/cio: use generic bitmap functions
  s390/chpid: make headers usable (again)

Pull tile fixes from Chris Metcalf:
 "This fixes one issue with compiler flags that can cause modules not to
  load, and cleans up some warnings with ELF_R_xxx defines."

* 'stable' of git://git.kernel.org/pub/scm/linux/kernel/git/cmetcalf/linux-tile:
  arch/tile: avoid build warnings from duplicate ELF_R_xxx #defines
  arch/tile: avoid generating .eh_frame information in modules

Pull ia64 fix from Tony Luck:
 "Fix from dhowells for UAPI fallout"

* tag 'please-pull-uapi-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux:
  UAPI: Make arch/ia64/include/asm/kvm_para.h generic

These are now provided in <asm-generic/module.h>, so clean up warnings
by not re-defining them in module.c.
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>

The tile tool chain uses the .eh_frame information for backtracing.
The vmlinux build drops any .eh_frame sections at link time, but when
present in kernel modules, it causes a module load failure due to the
presence of unsupported pc-relative relocations.  When compiling to
use compiler feedback support, the compiler by default omits .eh_frame
information, so we don't see this problem.  But when not using feedback,
we need to explicitly suppress the .eh_frame.
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Cc: stable@vger.kernel.org

Pull drm fixes from Dave Airlie:
 "Fixes for intel and nouveau mainly.

   - intel: disable HSW by default, sdvo fixes, link train regression
     fix
   - nouveau: acpi rom loading regression fix, with a few other fixes
     from the rework
   -core: just other minor fixes and race fixes for ttm."

* 'drm-fixes' of git://people.freedesktop.org/~airlied/linux: (24 commits)
  drm/ttm: Fix a theoretical race in ttm_bo_cleanup_refs()
  drm/ttm: Fix a theoretical race
  drm: platform: Don't initialize driver-private data
  drm/debugfs: remove redundant info from gem_names
  drm: fb: cma: Fail gracefully on allocation failure
  drm: fb: cma: Fix typo in debug message
  drm/nouveau/clock: fix missing pll type/addr when matching default entry
  drm/nouveau/fb: fix reporting of memory type on GF8+ IGPs
  drm/nv41/vm: don't init hw pciegart on boards with agp bridge
  drm/nouveau/bios: fetch full 4KiB block to determine ACPI ROM image size
  drm/nouveau: validate vbios size
  drm/nouveau: warn when trying to free mm which is still in use
  drm/nouveau: fix nouveau_mm/nouveau_mm_node leak
  drm/nouveau/bios: improve error handling when reading the vbios from ACPI
  drm/nouveau: handle same-fb page flips
  drm/i915: Initialize obj->pages before use by i915_gem_object_do_bit17_swizzle()
  drm/i915: Add no-lvds quirk for Supermicro X7SPA-H
  drm/i915: Insert i915_preliminary_hw_support variable.
  drm/i915: shut up spurious WARN in the gtt fault handler
  Revert "drm/i915: Try harder to complete DP training pattern 1"
  ...

Pull jfs fix from Dave Kleikamp:
 "Bug fix: Fix FITRIM argument handling"

* tag 'jfs-3.7-2' of git://github.com/kleikamp/linux-shaggy:
  jfs: Fix FITRIM argument handling

Pull ext4 fixes from Ted Ts'o:
 "Various bug fixes for ext4.  The most serious of them fixes a security
  bug (CVE-2012-4508) which leads to stale data exposure when we have
  fallocate racing against writes to files undergoing delayed
  allocation.  We also have two fixes for the metadata checksum feature,
  the most serious of which can cause the superblock to have a invalid
  checksum after a power failure."

* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
  ext4: Avoid underflow in ext4_trim_fs()
  ext4: Checksum the block bitmap properly with bigalloc enabled
  ext4: fix undefined bit shift result in ext4_fill_flex_info
  ext4: fix metadata checksum calculation for the superblock
  ext4: race-condition protection for ext4_convert_unwritten_extents_endio
  ext4: serialize fallocate with ext4_convert_unwritten_extents

Pull NFS client bugfixes from Trond Myklebust:
 - Do not call pnfs_return_layout() from an rpciod context
 - nfs4_ds_disconnect can cause Oopses.  Kill it...
 - Fix the return value for nfs_callback_start_svc
 - Fix a number of compile warnings

* tag 'nfs-for-3.7-2' of git://git.linux-nfs.org/projects/trondmy/linux-nfs:
  NFSv4: Fix the return value for nfs_callback_start_svc
  NFSv4.1: Declare osd_pri_2_pnfs_err(), objio_init_read/write to be static
  NFSv4: fs/nfs/nfs4getroot.c needs to include "internal.h"
  NFSv4.1: Use kcalloc() to allocate zeroed arrays instead of kzalloc()
  NFSv4.1: Do not call pnfs_return_layout() from an rpciod context
  NFSv4.1: Kill nfs4_ds_disconnect()

Pull regmap fix from Mark Brown:
 "regmap: Fix for dependencies for MMIO

  Trivial dependency issue, not noticed before as the only user of MMIO
  also needs I2C."

* tag 'regmap-fix-mmio' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regmap:
  regmap: select REGMAP if REGMAP_MMIO and REGMAP_IRQ enabled

In theory, that function could release the lru lock between
checking for bo on ddestroy list and a successful reserve if the bo
was already reserved, and the function was called with waiting reserves
allowed.
However, all current reservers of a bo on the ddestroy list would
atomically take the bo off the list after a successful reserve so this
race should not have been hit, so no need to backport for stable.

This patch also fixes a case found by Maarten Lankhorst where
ttm_mem_evict_first called with no_wait_gpu would incorrectly
spin waiting for bo idle if trying to evict a busy buffer that
also sits on the ddestroy list.
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

The ttm_mem_evict_first function could theoretically drop the
lru lock without retrying if a reservation from off the LRU list
ended up waiting.
However, since currently there are no users that could cause a wait
in that situation so this is not suitable for stable
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

Platform device drivers usually use the driver-private data for their
own purposes. Having it overwritten by drm_platform_init() is confusing
and error-prone.
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>

It's a relic of "drm: Convert proc files to seq_file and introduce debugfs",
which wrongly converted DRM_INFO + sprintf to 2 seq_printfs.
Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Ben Gamari <bgamari@gmail.com>
Cc: Eric Anholt <eric@anholt.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>

The drm_gem_cma_create() function never returns NULL but rather an error
encoded in the return value using the ERR_PTR() macro. Callers therefore
need to check for errors using the IS_ERR() macro. This change allows
drivers to handle contiguous DMA allocation failures gracefully.
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>

The debug message showing the resolution of a framebuffer to be
allocated is missing a closing parenthesis.
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>

Currently if len argument in ext4_trim_fs() is smaller than one block,
the 'end' variable underflow. Avoid that by returning EINVAL if len is
smaller than file system block.

Also remove useless unlikely().
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org

KVM_PV_REASON_PAGE_NOT_PRESENT kicks cpu out of idleness, but we haven't
marked that spot as an exit from idleness.

Not doing so can cause RCU warnings such as:

[  732.788386] ===============================
[  732.789803] [ INFO: suspicious RCU usage. ]
[  732.790032] 3.7.0-rc1-next-20121019-sasha-00002-g6d8d02d-dirty #63 Tainted: G        W
[  732.790032] -------------------------------
[  732.790032] include/linux/rcupdate.h:738 rcu_read_lock() used illegally while idle!
[  732.790032]
[  732.790032] other info that might help us debug this:
[  732.790032]
[  732.790032]
[  732.790032] RCU used illegally from idle CPU!
[  732.790032] rcu_scheduler_active = 1, debug_locks = 1
[  732.790032] RCU used illegally from extended quiescent state!
[  732.790032] 2 locks held by trinity-child31/8252:
[  732.790032]  #0:  (&rq->lock){-.-.-.}, at: [<ffffffff83a67528>] __schedule+0x178/0x8f0
[  732.790032]  #1:  (rcu_read_lock){.+.+..}, at: [<ffffffff81152bde>] cpuacct_charge+0xe/0x200
[  732.790032]
[  732.790032] stack backtrace:
[  732.790032] Pid: 8252, comm: trinity-child31 Tainted: G        W    3.7.0-rc1-next-20121019-sasha-00002-g6d8d02d-dirty #63
[  732.790032] Call Trace:
[  732.790032]  [<ffffffff8118266b>] lockdep_rcu_suspicious+0x10b/0x120
[  732.790032]  [<ffffffff81152c60>] cpuacct_charge+0x90/0x200
[  732.790032]  [<ffffffff81152bde>] ? cpuacct_charge+0xe/0x200
[  732.790032]  [<ffffffff81158093>] update_curr+0x1a3/0x270
[  732.790032]  [<ffffffff81158a6a>] dequeue_entity+0x2a/0x210
[  732.790032]  [<ffffffff81158ea5>] dequeue_task_fair+0x45/0x130
[  732.790032]  [<ffffffff8114ae29>] dequeue_task+0x89/0xa0
[  732.790032]  [<ffffffff8114bb9e>] deactivate_task+0x1e/0x20
[  732.790032]  [<ffffffff83a67c29>] __schedule+0x879/0x8f0
[  732.790032]  [<ffffffff8117e20d>] ? trace_hardirqs_off+0xd/0x10
[  732.790032]  [<ffffffff810a37a5>] ? kvm_async_pf_task_wait+0x1d5/0x2b0
[  732.790032]  [<ffffffff83a67cf5>] schedule+0x55/0x60
[  732.790032]  [<ffffffff810a37c4>] kvm_async_pf_task_wait+0x1f4/0x2b0
[  732.790032]  [<ffffffff81139e50>] ? abort_exclusive_wait+0xb0/0xb0
[  732.790032]  [<ffffffff81139c25>] ? prepare_to_wait+0x25/0x90
[  732.790032]  [<ffffffff810a3a66>] do_async_page_fault+0x56/0xa0
[  732.790032]  [<ffffffff83a6a6e8>] async_page_fault+0x28/0x30
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Acked-by: Gleb Natapov <gleb@redhat.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Reviewed-by: Chegu Vinod  <chegu_vinod@hp.com>
Tested-by: Chegu Vinod <chegu_vinod@hp.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

We can not directly call kvm_release_pfn_clean to release the pfn
since we can meet noslot pfn which is used to cache mmio info into
spte
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Avi Kivity <avi@redhat.com>

Fixes from Ben, off note:
ACPI ROM regression fix,
some IGP and AGP regressions fixes from rework fallout.

* 'drm-nouveau-fixes' of git://git.freedesktop.org/git/nouveau/linux-2.6:
  drm/nouveau/clock: fix missing pll type/addr when matching default entry
  drm/nouveau/fb: fix reporting of memory type on GF8+ IGPs
  drm/nv41/vm: don't init hw pciegart on boards with agp bridge
  drm/nouveau/bios: fetch full 4KiB block to determine ACPI ROM image size
  drm/nouveau: validate vbios size
  drm/nouveau: warn when trying to free mm which is still in use
  drm/nouveau: fix nouveau_mm/nouveau_mm_node leak
  drm/nouveau/bios: improve error handling when reading the vbios from ACPI
  drm/nouveau: handle same-fb page flips

Fix the warning:

  kernel/module_signing.c:195:2: warning: format '%lu' expects type 'long unsigned int', but argument 3 has type 'size_t'

by using the proper 'z' modifier for printing a size_t.
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull m68k updates from Geert Uytterhoeven:
 "Just the expected UAPI disintegration and the "new" kcmp syscall."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/geert/linux-m68k:
  m68k: Wire up kcmp
  m68k: Remove empty #ifdef/#else/#endif block
  UAPI: (Scripted) Disintegrate arch/m68k/include/asm

Commit 7f8d4cad ("Input: extend the number of event (and other)
devices") made evdev, joydev and mousedev to embed struct cdev into
their respective structures representing input devices.

Unfortunately character device structure may outlive the parent
structure unless we do not set it up as parent of character device so
that it will stay pinned until character device is freed.

Also, now that parent structure is pinned while character device exists
we do not need to pin and unpin it every time user opens or closes it.
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

In certain cases (for example when a cdev structure is embedded into
another object whose lifetime is controlled by a separate kobject) it is
beneficial to tie lifetime of another object to the lifetime of
character device so that related object is not freed until after
char_dev object is freed.

To achieve this let's pin kobject's parent when doing cdev_add() and
unpin when last reference to cdev structure is being released.
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This issue is a regression from 70790f4f,
and causes us to miss a special-case for C51 (NV4E) chipsets and return
the wrong reference frequency for the VPLLs.

Should fix fdo#56202
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

In mke2fs, we only checksum the whole bitmap block and it is right.
While in the kernel, we use EXT4_BLOCKS_PER_GROUP to indicate the
size of the checksumed bitmap which is wrong when we enable bigalloc.
The right size should be EXT4_CLUSTERS_PER_GROUP and this patch fixes
it.

Also as every caller of ext4_block_bitmap_csum_set and
ext4_block_bitmap_csum_verify pass in EXT4_BLOCKS_PER_GROUP(sb)/8,
we'd better removes this parameter and sets it in the function itself.
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
Cc: stable@vger.kernel.org

Purely a cosmetic issue at this point.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

Buggy firmware leads to bad things happening otherwise..
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

Without checking, we could detect vbios size as 0, allocate 0-byte array
(kmalloc returns invalid pointer for such allocation) and crash in
nouveau_bios_score while checking for vbios signature.
Reported-by: Heinz Diehl <htd@fritha.org>
Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>