Commit Graph

103 Commits

Author SHA1 Message Date
Chris Wilson 381b943b07 drm/i915: Remove i915_address_space.start
Once upon a time, back in the UMS days, we supported userspace
initialising the GTT and sharing portions of the GTT with other users.
Now, we own the GTT (both global and per-process) and the tables always
start at 0 - so we can remove i915_address_space.start and forget about
this old complication.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170215084357.19977-20-chris@chris-wilson.co.uk
2017-02-15 10:07:32 +00:00
Chris Wilson f40a7b7558 drm/i915: Initial selftests for exercising eviction
Very simple tests to just ask eviction to find some free space in a full
GTT and one with some available space.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170213171558.20942-41-chris@chris-wilson.co.uk
2017-02-13 20:46:47 +00:00
Daniel Vetter 51a831a772 Merge remote-tracking branch 'airlied/drm-next' into drm-intel-next-queued
Chris Wilson needs the new drm_driver->release callback to make sure
the shiny new dma-buf testcases don't oops the driver on unload.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
2017-02-10 16:27:24 +01:00
Chris Wilson a6508ded2a drm/i915: Use page coloring to provide the guard page at the end of the GTT
As we now mark the reserved hole (drm_mm.head_node) with the special
UNEVICTABLE color, we can use the page coloring to avoid prefetching of
the CS beyond the end of the GTT.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170206084547.27921-3-chris@chris-wilson.co.uk
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
2017-02-06 13:46:40 +00:00
Chris Wilson 4e64e5539d drm: Improve drm_mm search (and fix topdown allocation) with rbtrees
The drm_mm range manager claimed to support top-down insertion, but it
was neither searching for the top-most hole that could fit the
allocation request nor fitting the request to the hole correctly.

In order to search the range efficiently, we create a secondary index
for the holes using either their size or their address. This index
allows us to find the smallest hole or the hole at the bottom or top of
the range efficiently, whilst keeping the hole stack to rapidly service
evictions.

v2: Search for holes both high and low. Rename flags to mode.
v3: Discover rb_entry_safe() and use it!
v4: Kerneldoc for enum drm_mm_insert_mode.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Russell King <rmk+kernel@armlinux.org.uk>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Christian Gmeiner <christian.gmeiner@gmail.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Stephen Warren <swarren@wwwdotorg.org>
Cc: Alexandre Courbot <gnurou@gmail.com>
Cc: Eric Anholt <eric@anholt.net>
Cc: Sinclair Yeh <syeh@vmware.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com> # vmwgfx
Reviewed-by: Lucas Stach <l.stach@pengutronix.de> #etnaviv
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170202210438.28702-1-chris@chris-wilson.co.uk
2017-02-03 11:10:32 +01:00
Chris Wilson 16ee20619f drm/i915: Detect vma reserved for execbuf in evict-for-node
The vma->exec_list is still the only means we have for both reserving an
object in execbuf, and for constructing the eviction list. So during the
construction of the eviction list, we must treat anything already on the
exec_list as being pinned.

Yes, this sharing of two semantically different lists will be fixed! But
in the meantime, we have the issue that this is tripping up CI since we
started using i915_gem_gtt_reserve_node() + i915_gem_evict_for_node()
from the regular execbuf reservation path in commit 606fec956c
("drm/i915: Prefer random replacement before eviction search"):

[  108.424063] kernel BUG at drivers/gpu/drm/i915/i915_vma.h:254!
[  108.424072] invalid opcode: 0000 [#1] PREEMPT SMP
[  108.424079] Modules linked in: snd_hda_intel i915 intel_powerclamp coretemp crct10dif_pclmul crc32_pclmul ghash_clmulni_intel snd_hda_codec_hdmi snd_hda_codec_generic snd_hda_codec snd_hwdep snd_hda_core mei_me snd_pcm lpc_ich mei sdhci_pci sdhci mmc_core e1000e ptp pps_core [last unloaded: i915]
[  108.424132] CPU: 1 PID: 6865 Comm: gem_cs_tlb Tainted: G     U          4.10.0-rc3-CI-CI_DRM_2049+ #1
[  108.424143] Hardware name: Hewlett-Packard HP EliteBook 8440p/172A, BIOS 68CCU Ver. F.24 09/13/2013
[  108.424154] task: ffff88012ae22600 task.stack: ffffc90000a14000
[  108.424220] RIP: 0010:i915_gem_evict_for_node+0x237/0x410 [i915]
[  108.424229] RSP: 0018:ffffc90000a17a58 EFLAGS: 00010202
[  108.424237] RAX: 0000000000005871 RBX: ffff88012d1ad778 RCX: 0000000000000000
[  108.424246] RDX: 000000007ffff000 RSI: ffffc90000a17a68 RDI: ffff880127e694d8
[  108.424255] RBP: ffffc90000a17aa0 R08: ffffc90000a17a68 R09: 0000000000000000
[  108.424264] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000080000000
[  108.424273] R13: ffffc90000a17a68 R14: ffff880127e694d8 R15: ffffffffa0387330
[  108.424283] FS:  00007f8236e3d8c0(0000) GS:ffff880137c40000(0000) knlGS:0000000000000000
[  108.424293] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  108.424305] CR2: 00007f82347a2000 CR3: 000000012c866000 CR4: 00000000000006e0
[  108.424317] Call Trace:
[  108.424368]  i915_gem_gtt_reserve+0x67/0x80 [i915]
[  108.424424]  __i915_vma_do_pin+0x248/0x620 [i915]
[  108.424487]  ? __i915_vma_do_pin+0x162/0x620 [i915]
[  108.424540]  i915_gem_execbuffer_reserve_vma.isra.8+0x153/0x1f0 [i915]
[  108.424591]  i915_gem_execbuffer_reserve.isra.9+0x40e/0x440 [i915]
[  108.424643]  i915_gem_do_execbuffer.isra.15+0x6d9/0x1b20 [i915]
[  108.424696]  i915_gem_execbuffer2+0xc0/0x250 [i915]
[  108.424712]  drm_ioctl+0x200/0x450
[  108.424760]  ? i915_gem_execbuffer+0x330/0x330 [i915]
[  108.424776]  do_vfs_ioctl+0x90/0x6e0
[  108.424789]  ? up_read+0x1a/0x40
[  108.424800]  ? trace_hardirqs_on_caller+0x122/0x1b0
[  108.424813]  SyS_ioctl+0x3c/0x70
[  108.424828]  entry_SYSCALL_64_fastpath+0x1c/0xb1
[  108.424839] RIP: 0033:0x7f8235867357
[  108.424848] RSP: 002b:00007ffdc14504c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[  108.424866] RAX: ffffffffffffffda RBX: 00007ffdc1450600 RCX: 00007f8235867357
[  108.424878] RDX: 00007ffdc14505a0 RSI: 0000000040406469 RDI: 0000000000000003
[  108.424890] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000022
[  108.424903] R10: 0000000000000007 R11: 0000000000000246 R12: 0000000000000002
[  108.424915] R13: 0000000000419101 R14: 00007ffdc1450600 R15: 00007ffdc14505f0
[  108.424928] Code: 45 b8 8b 4d c0 4c 89 f2 48 89 de ff d0 49 8b 07 4c 8b 45 b8 48 85 c0 75 dd 65 ff 0d d4 a1 c8 5f 0f 84 47 01 00 00 e9 0d fe ff ff <0f> 0b 45 31 f6 4c 8b 65 c8 49 8b 04 24 4d 39 ec 49 8d 9c 24 28
[  108.425055] RIP: i915_gem_evict_for_node+0x237/0x410 [i915] RSP: ffffc90000a17a58

Fixes: 172ae5b4c8 ("drm/i915: Fix i915_gem_evict_for_vma (soft-pinning)")
Fixes: 606fec956c ("drm/i915: Prefer random replacement before eviction search")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170111182132.19174-1-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
2017-01-12 07:51:49 +00:00
Chris Wilson 625d988acc drm/i915: Extract reserving space in the GTT to a helper
Extract drm_mm_reserve_node + calling i915_gem_evict_for_node into its
own routine so that it can be shared rather than duplicated.

v2: Kerneldoc

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: igvt-g-dev@lists.01.org
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170111112312.31493-2-chris@chris-wilson.co.uk
2017-01-11 12:28:13 +00:00
Chris Wilson f51455d442 drm/i915: Replace 4096 with PAGE_SIZE or I915_GTT_PAGE_SIZE
Start converting over from the byte count to its semantic macro, either
we want to allocate the size of a physical page in main memory or we
want the size of a virtual page in the GTT. 4096 could mean either, but
PAGE_SIZE and I915_GTT_PAGE_SIZE are explicit and should help improve
code comprehension and future changes. In the future, we may want to use
variable GTT page sizes and so have the challenge of knowing which
hardcoded values were used to represent a physical page vs the virtual
page.

v2: Look for a few more 4096s to convert, discover IS_ALIGNED().
v3: 4096ul paranoia, make fence alignment a distinct value of 4096, keep
bdw stolen w/a as 4096 until we know better.
v4: Add asserts that i915_vma_insert() start/end are aligned to GTT page
sizes.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170110144734.26052-1-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
2017-01-10 20:54:32 +00:00
Chris Wilson 121dfbb2a2 drm/i915: Clear ret before unbinding in i915_gem_evict_something()
Missed when rebasing patches, I failed to set ret to zero before
starting the unbind loop (which depends upon ret being zero).

Reported-by: Matthew Auld <matthew.william.auld@gmail.com>
Fixes: 9332f3b1b9 ("drm/i915: Combine loops within i915_gem_evict_something")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170105155940.10033-1-chris@chris-wilson.co.uk
Reviewed-by: Matthew Auld <matthew.william.auld@gmail.com>
Cc: <stable@vger.kernel.org> # v4.9+
2017-01-05 16:44:51 +00:00
Daniel Vetter ef426c1038 Merge tag 'drm-misc-next-2016-12-30' of git://anongit.freedesktop.org/git/drm-misc into drm-intel-next-queued
Directly merge drm-misc into drm-intel since Dave is on vacation and
we need the various drm-misc patches (fb format rework, drm mm fixes,
selftest framework and others). Also pulled back -rc2 in first to
resync with drm-intel-fixes and make sure I can reuse the exact rerere
solutions from drm-tip for safety, and because I'm lazy.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
2017-01-04 11:41:10 +01:00
Chris Wilson 3fa489dabe drm: Apply tight eviction scanning to color_adjust
Using mm->color_adjust makes the eviction scanner much tricker since we
don't know the actual neighbours of the target hole until after it is
created (after scanning is complete). To work out whether we need to
evict the neighbours because they impact upon the hole, we have to then
check the hole afterwards - requiring an extra step in the user of the
eviction scanner when they apply color_adjust.

v2: Massage kerneldoc.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161222083641.2691-34-chris@chris-wilson.co.uk
2016-12-28 13:23:06 +01:00
Chris Wilson 0b04d474a6 drm: Compute tight evictions for drm_mm_scan
Compute the minimal required hole during scan and only evict those nodes
that overlap. This enables us to reduce the number of nodes we need to
evict to the bare minimum.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161222083641.2691-31-chris@chris-wilson.co.uk
2016-12-28 11:50:55 +01:00
Chris Wilson 2c4b389518 drm: Unconditionally do the range check in drm_mm_scan_add_block()
Doing the check is trivial (low cost in comparison to overall eviction)
and helps simplify the code.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161222083641.2691-29-chris@chris-wilson.co.uk
2016-12-28 11:50:28 +01:00
Chris Wilson 9a71e27788 drm: Extract struct drm_mm_scan from struct drm_mm
The scan state occupies a large proportion of the struct drm_mm and is
rarely used and only contains temporary state. That makes it suitable to
moving to its struct and onto the stack of the callers.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
[danvet: Fix up etnaviv to compile, was missing a BUG_ON.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2016-12-27 16:44:13 +01:00
Chris Wilson 7155b057c6 drm/i915: Retire before attempting to evict from the active lists
Some object retain an extra pin whilst they are active (e.g. contexts).
This excludes them from being considered for eviction unless we idle the
GPU. If before we look at the active list, we retire beforehand we can
hopefully remove a few excess pins and reduce the amount of searching
required.

v2: Similar principle applies to evict_for_vma

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20161209150555.602-1-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
2016-12-12 12:25:32 +00:00
Chris Wilson 172ae5b4c8 drm/i915: Fix i915_gem_evict_for_vma (soft-pinning)
Soft-pinning depends upon being able to check for availabilty of an
interval and evict overlapping object from a drm_mm range manager very
quickly. Currently it uses a linear list, and so performance is dire and
not suitable as a general replacement. Worse, the current code will oops
if it tries to evict an active buffer.

It also helps if the routine reports the correct error codes as expected
by its callers and emits a tracepoint upon use.

For posterity since the wrong patch was pushed (i.e. that missed these
key points and had known bugs), this is the changelog that should have
been on commit 506a8e87d8 ("drm/i915: Add soft-pinning API for
execbuffer"):

Userspace can pass in an offset that it presumes the object is located
at. The kernel will then do its utmost to fit the object into that
location. The assumption is that userspace is handling its own object
locations (for example along with full-ppgtt) and that the kernel will
rarely have to make space for the user's requests.

This extends the DRM_IOCTL_I915_GEM_EXECBUFFER2 to do the following:
* if the user supplies a virtual address via the execobject->offset
  *and* sets the EXEC_OBJECT_PINNED flag in execobject->flags, then
  that object is placed at that offset in the address space selected
  by the context specifier in execbuffer.
* the location must be aligned to the GTT page size, 4096 bytes
* as the object is placed exactly as specified, it may be used by this
  execbuffer call without relocations pointing to it

It may fail to do so if:
* EINVAL is returned if the object does not have a 4096 byte aligned
  address
* the object conflicts with another pinned object (either pinned by
  hardware in that address space, e.g. scanouts in the aliasing ppgtt)
  or within the same batch.
  EBUSY is returned if the location is pinned by hardware
  EINVAL is returned if the location is already in use by the batch
* EINVAL is returned if the object conflicts with its own alignment (as meets
  the hardware requirements) or if the placement of the object does not fit
  within the address space

All other execbuffer errors apply.

Presence of this execbuf extension may be queried by passing
I915_PARAM_HAS_EXEC_SOFTPIN to DRM_IOCTL_I915_GETPARAM and checking for
a reported value of 1 (or greater).

v2: Combine the hole/adjusted-hole ENOSPC checks
v3: More color, more splitting, more blurb.

Fixes: 506a8e87d8 ("drm/i915: Add soft-pinning API for execbuffer")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161205142941.21965-2-chris@chris-wilson.co.uk
2016-12-05 20:49:17 +00:00
Chris Wilson 49d73912cb drm/i915: Convert vm->dev backpointer to vm->i915
99% of the time we access i915_address_space->dev we want the i915
device and not the drm device, so let's store the drm_i915_private
backpointer instead. The only real complication here are the inlines
in i915_vma.h where drm_i915_private is not yet defined and so we have
to choose an alternate path for our asserts.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161129095008.32622-1-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
2016-11-29 11:38:00 +00:00
Chris Wilson 80b204bce8 drm/i915: Enable multiple timelines
With the infrastructure converted over to tracking multiple timelines in
the GEM API whilst preserving the efficiency of using a single execution
timeline internally, we can now assign a separate timeline to every
context with full-ppgtt.

v2: Add a comment to indicate the xfer between timelines upon submission.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161028125858.23563-35-chris@chris-wilson.co.uk
2016-10-28 20:53:57 +01:00
Chris Wilson 4c7d62c6b8 drm/i915: Markup GEM API with lockdep asserts
Add lockdep_assert_held(struct_mutex) to the API preamble of the
internal GEM interfaces.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161028125858.23563-9-chris@chris-wilson.co.uk
2016-10-28 20:53:45 +01:00
Chris Wilson 275f039db5 drm/i915: Move user fault tracking to a separate list
We want to decouple RPM and struct_mutex, but currently RPM has to walk
the list of bound objects and remove userspace mmapping before we
suspend (otherwise userspace may continue to access the GTT whilst it is
powered down). This currently requires the struct_mutex to walk the
bound_list, but if we move that to a separate list and lock we can take
the first step towards removing the struct_mutex.

v2: Split runtime suspend unmapping vs regular unmapping, to make the
locking (and barriers) clearer. Add the object to the userfault_list
prior to inserting the first PTE, the race between add/revoke depends
upon struct_mutex for regular unmappings and rpm for runtime-suspend.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> #v1
Link: http://patchwork.freedesktop.org/patch/msgid/20161024124218.18252-1-chris@chris-wilson.co.uk
2016-10-24 13:45:35 +01:00
Akash Goel 3b3f1650b1 drm/i915: Allocate intel_engine_cs structure only for the enabled engines
With the possibility of addition of many more number of rings in future,
the drm_i915_private structure could bloat as an array, of type
intel_engine_cs, is embedded inside it.
	struct intel_engine_cs engine[I915_NUM_ENGINES];
Though this is still fine as generally there is only a single instance of
drm_i915_private structure used, but not all of the possible rings would be
enabled or active on most of the platforms. Some memory can be saved by
allocating intel_engine_cs structure only for the enabled/active engines.
Currently the engine/ring ID is kept static and dev_priv->engine[] is simply
indexed using the enums defined in intel_engine_id.
To save memory and continue using the static engine/ring IDs, 'engine' is
defined as an array of pointers.
	struct intel_engine_cs *engine[I915_NUM_ENGINES];
dev_priv->engine[engine_ID] will be NULL for disabled engine instances.

There is a text size reduction of 928 bytes, from 1028200 to 1027272, for
i915.o file (but for i915.ko file text size remain same as 1193131 bytes).

v2:
- Remove the engine iterator field added in drm_i915_private structure,
  instead pass a local iterator variable to the for_each_engine**
  macros. (Chris)
- Do away with intel_engine_initialized() and instead directly use the
  NULL pointer check on engine pointer. (Chris)

v3:
- Remove for_each_engine_id() macro, as the updated macro for_each_engine()
  can be used in place of it. (Chris)
- Protect the access to Render engine Fault register with a NULL check, as
  engine specific init is done later in Driver load sequence.

v4:
- Use !!dev_priv->engine[VCS] style for the engine check in getparam. (Chris)
- Kill the superfluous init_engine_lists().

v5:
- Cleanup the intel_engines_init() & intel_engines_setup(), with respect to
  allocation of intel_engine_cs structure. (Chris)

v6:
- Rebase.

v7:
- Optimize the for_each_engine_masked() macro. (Chris)
- Change the type of 'iter' local variable to enum intel_engine_id. (Chris)
- Rebase.

v8: Rebase.

v9: Rebase.

v10:
- For index calculation use engine ID instead of pointer based arithmetic in
  intel_engine_sync_index() as engine pointers are not contiguous now (Chris)
- For appropriateness, rename local enum variable 'iter' to 'id'. (Joonas)
- Use for_each_engine macro for cleanup in intel_engines_init() and remove
  check for NULL engine pointer in cleanup() routines. (Joonas)

v11: Rebase.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Akash Goel <akash.goel@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1476378888-7372-1-git-send-email-akash.goel@intel.com
2016-10-14 09:58:43 +01:00
Chris Wilson 22dd3bb919 drm/i915: Mark up all locked waiters
In the next patch we want to handle reset directly by a locked waiter in
order to avoid issues with returning before the reset is handled. To
handle the reset, we must first know whether we hold the struct_mutex.
If we do not hold the struct_mtuex we can not perform the reset, but we do
not block the reset worker either (and so we can just continue to wait for
request completion) - otherwise we must relinquish the mutex.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160909131201.16673-10-chris@chris-wilson.co.uk
2016-09-09 14:23:03 +01:00
Chris Wilson ea746f3659 drm/i915: Expand bool interruptible to pass flags to i915_wait_request()
We need finer control over wakeup behaviour during i915_wait_request(),
so expand the current bool interruptible to a bitmask.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160909131201.16673-9-chris@chris-wilson.co.uk
2016-09-09 14:23:03 +01:00
Chris Wilson 821188778b drm/i915: Choose not to evict faultable objects from the GGTT
Often times we do not want to evict mapped objects from the GGTT as
these are quite expensive to teardown and frequently reused (causing an
equally, if not more so, expensive setup). In particular, when faulting
in a new object we want to avoid evicting an active object, or else we
may trigger a page-fault-of-doom as we ping-pong between evicting two
objects.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160818161718.27187-26-chris@chris-wilson.co.uk
2016-08-18 22:36:55 +01:00
Chris Wilson dcff85c844 drm/i915: Enable i915_gem_wait_for_idle() without holding struct_mutex
The principal motivation for this was to try and eliminate the
struct_mutex from i915_gem_suspend - but we still need to hold the mutex
current for the i915_gem_context_lost(). (The issue there is that there
may be an indirect lockdep cycle between cpu_hotplug (i.e. suspend) and
struct_mutex via the stop_machine().) For the moment, enabling last
request tracking for the engine, allows us to do busyness checking and
waiting without requiring the struct_mutex - which is useful in its own
right.

As a side-effect of having a robust means for tracking engine busyness,
we can replace our other busyness heuristic, that of comparing against
the last submitted seqno. For paranoid reasons, we have a semi-ordered
check of that seqno inside the hangchecker, which we can now improve to
an ordered check of the engine's busyness (removing a locked xchg in the
process).

v2: Pass along "bool interruptible" as being unlocked we cannot rely on
i915->mm.interruptible being stable or even under our control.
v3: Replace check Ironlake i915_gpu_busy() with the common precalculated value

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470388464-28458-6-git-send-email-chris@chris-wilson.co.uk
2016-08-05 10:54:37 +01:00
Chris Wilson 20dfbde463 drm/i915: Wrap vma->pin_count accessors with small inline helpers
In the next few patches, the VMA pinning API is overhauled and to reduce
the churn we pull out the update to the accessors into a prep patch.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470324762-2545-14-git-send-email-chris@chris-wilson.co.uk
2016-08-04 20:19:58 +01:00
Chris Wilson 2ffffd0f85 drm/i915: Fix up vma alignment to be u64
This is not the full fix, as we are required to percolate the u64 nature
down through the drm_mm stack, but this is required now to prevent
explosions due to mismatch between execbuf (eb_vma_misplaced) and vma
binding (i915_vma_misplaced) - and reduces the risk of spurious changes
as we adjust the vma interface in the next patches.

v2: long long casts not required for u64 printk (%llx)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470324762-2545-6-git-send-email-chris@chris-wilson.co.uk
2016-08-04 20:19:52 +01:00
Chris Wilson e522ac2324 drm/i915: Remove surplus drm_device parameter to i915_gem_evict_something()
Eviction is VM local, so we can ignore the significance of the
drm_device in the caller, and leave it to i915_gem_evict_something() to
manage itself.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470324762-2545-2-git-send-email-chris@chris-wilson.co.uk
2016-08-04 20:19:50 +01:00
Chris Wilson 9332f3b1b9 drm/i915: Combine loops within i915_gem_evict_something
Slight micro-optimise to produce combine loops so that gcc is able to
optimise the inner-loops concisely. Since we are reviewing the loops, we
can update the comments to describe the current state of affairs, in
particular the distinction between evicting from the global GTT (which
may contain untracked items and transient global pins) and the
per-process GTT.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470324762-2545-1-git-send-email-chris@chris-wilson.co.uk
2016-08-04 20:19:49 +01:00
Chris Wilson b1f788c6ac drm/i915: Release vma when the handle is closed
In order to prevent a leak of the vma on shared objects, we need to
hook into the object_close callback to destroy the vma on the object for
this file. However, if we destroyed that vma immediately we may cause
unexpected application stalls as we try to unbind a busy vma - hence we
defer the unbind to when we retire the vma.

v2: Keep vma allocated until closed. This is useful for a later
optimisation, but it is required now in order to handle potential
recursion of i915_vma_unbind() by retiring itself.
v3: Comments are important.

Testcase: igt/gem_ppggtt/flink-and-close-vma-leak
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470293567-10811-26-git-send-email-chris@chris-wilson.co.uk
2016-08-04 08:09:33 +01:00
Chris Wilson f8c417cdb1 drm/i915: Rename drm_gem_object_unreference in preparation for lockless free
Ultimately wraps kref_put(), so adopt its nomenclature for consistency
with other subsystems.

s/drm_gem_object_unreference/i915_gem_object_put/

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1469005202-9659-6-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1469017917-15134-5-git-send-email-chris@chris-wilson.co.uk
2016-07-20 13:40:12 +01:00
Chris Wilson 25dc556a2a drm/i915: Wrap drm_gem_object_reference in i915_gem_object_get
Ultimately wraps kref_get(), so adopt its nomenclature for consistency
with other subsystems.

s/drm_gem_object_reference/i915_gem_object_get/

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1469005202-9659-5-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Dave Gordon <david.s.gordon@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1469017917-15134-4-git-send-email-chris@chris-wilson.co.uk
2016-07-20 13:40:11 +01:00
Chris Wilson 945657b461 drm/i915/evict: Always switch away from the current context
Currently execlists is exempt from emitting a request to switch each
ring away from the current context over to the dev_priv->kernel_context
(for whatever reason, just under execlists the GGTT is unlikely to be as
fragmented, however the switch may help in some extreme cases). Extract
the switcher and enable it for execlsts as well, as we need to do so in
a later patch to force the context switch before suspend. (And since for
that switch we explicitly require the disposable kernel context, rename
the extracted function.)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1468590980-6186-1-git-send-email-chris@chris-wilson.co.uk
2016-07-15 20:40:53 +01:00
Chris Wilson 883445d43e drm/i915: Only switch to default context when evicting from GGTT
The contexts only pin space within the global GTT. Therefore forcing the
switch to the perma-pinned kernel context only has an effect when trying
to evict from and find room within the global GTT. We can then restrict
the switch to only when operating on the default context. This is mostly
a no-op as full-ppgtt only exists with execlists at present which skips
the context switch anyway.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1466776558-21516-7-git-send-email-chris@chris-wilson.co.uk
2016-06-24 15:03:32 +01:00
Chris Wilson 6e5a5beb8e drm/i915: Split idling from forcing context switch
We only need to force a switch to the kernel context placeholder during
eviction. All other uses of i915_gpu_idle() just want to wait until
existing work on the GPU is idle. Rename i915_gpu_idle() to
i915_gem_wait_for_idle() to avoid any implications about "parking" the
context first.

v2: Tweak an error message if the wait fails for the ilk vtd w/a

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1466776558-21516-6-git-send-email-chris@chris-wilson.co.uk
2016-06-24 15:03:14 +01:00
Chris Wilson c033666a94 drm/i915: Store a i915 backpointer from engine, and use it
text	   data	    bss	    dec	    hex	filename
6309351	3578714	 696320	10584385	 a18141	vmlinux
6308391	3578714	 696320	10583425	 a17d81	vmlinux

Almost 1KiB of code reduction.

v2: More s/INTEL_INFO()->gen/INTEL_GEN()/ and IS_GENx() conversions

   text	   data	    bss	    dec	    hex	filename
6304579	3578778	 696320	10579677	 a16edd	vmlinux
6303427	3578778	 696320	10578525	 a16a5d	vmlinux

Now over 1KiB!

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1462545621-30125-3-git-send-email-chris@chris-wilson.co.uk
2016-05-09 13:41:24 +01:00
Chris Wilson 1c7f4bca5a drm/i915: Rename vma->*_list to *_link for consistency
Elsewhere we have adopted the convention of using '_link' to denote
elements in the list (and '_list' for the actual list_head itself), and
that the name should indicate which list the link belongs to (and
preferrably not just where the link is being stored).

s/vma_link/obj_link/ (we iterate over obj->vma_list)
s/mm_list/vm_link/ (we iterate over vm->[in]active_list)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
2016-02-26 13:15:39 +00:00
Chris Wilson 506a8e87d8 drm/i915: Add soft-pinning API for execbuffer
Userspace can pass in an offset that it presumes the object is located
at. The kernel will then do its utmost to fit the object into that
location. The assumption is that userspace is handling its own object
locations (for example along with full-ppgtt) and that the kernel will
rarely have to make space for the user's requests.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

v2: Fixed incorrect eviction found by Michal Winiarski - fix suggested by Chris
Wilson.  Fixed incorrect error paths causing crash found by Michal Winiarski.
(Not published externally)

v3: Rebased because of trivial conflict in object_bind_to_vm.  Fixed eviction
to allow eviction of soft-pinned objects when another soft-pinned object used
by a subsequent execbuffer overlaps reported by Michal Winiarski.
(Not published externally)

v4: Moved soft-pinned objects to the front of ordered_vmas so that they are
pinned first after an address conflict happens to avoid repeated conflicts in
rare cases (Suggested by Chris Wilson).  Expanded comment on
drm_i915_gem_exec_object2.offset to cover this new API.

v5: Added I915_PARAM_HAS_EXEC_SOFTPIN parameter for detecting this capability
(Kristian). Added check for multiple pinnings on eviction (Akash). Made sure
buffers are not considered misplaced without the user specifying
EXEC_OBJECT_SUPPORTS_48B_ADDRESS.  User must assume responsibility for any
addressing workarounds.  Updated object2.offset field comment again to clarify
NO_RELOC case (Chris).  checkpatch cleanup.

v6: Trivial rebase on latest drm-intel-nightly

v7: Catch attempts to pin above the max virtual address size and return
EINVAL (Tvrtko). Decouple EXEC_OBJECT_SUPPORTS_48B_ADDRESS and
EXEC_OBJECT_PINNED flags, user must pass both flags in any attempt to pin
something at an offset above 4GB (Chris, Daniel Vetter).

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Akash Goel <akash.goel@intel.com>
Cc: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Cc: Zou Nanhai <nanhai.zou@intel.com>
Cc: Kristian Høgsberg <hoegsberg@gmail.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: Michel Thierry <michel.thierry@intel.com>
Acked-by: PDT
Signed-off-by: Thomas Daniel <thomas.daniel@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1449575707-20933-1-git-send-email-thomas.daniel@intel.com
2015-12-09 10:20:17 +00:00
Chris Wilson ce8daef358 drm/i915: Remove dead i915_gem_evict_everything()
With UMS gone, we no longer use it during suspend. And with the last
user removed from the shrinker, we can remove the dead code.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2015-10-07 16:05:40 +02:00
Daniel Vetter eb0b44adc0 drm/i915: kerneldoc for i915_gem_shrinker.c
And remove one bogus * from i915_gem_gtt.c since that's not a
kerneldoc there.

v2: Review from Chris:
- Clarify memory space to better distinguish from address space.
- Add note that shrink doesn't guarantee the freed memory and that
  users must fall back to shrink_all.
- Explain how pinning ties in with eviction/shrinker.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2015-03-20 11:48:16 +01:00
Ben Widawsky b9b5dce5e7 drm/i915: Add some extra guards in evict_vm
v2: Use WARN_ONs (Daniel)

Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2015-01-06 09:07:59 +01:00
Daniel Vetter 7838a63a53 drm/i915: Include i915_gem_evict.c kerneldoc into the drm docbook
I've written these long before we've had a reasonable docbook
structure, and naturally they've gone stale. Fix this up asap.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
2015-01-06 09:07:59 +01:00
Michel Thierry cf30362674 drm/i915: fix another use-after-free in i915_gem_evict_everything
Also here, i915_gem_evict_vm causes an unbind, which can end up dropping
the last ref to the ppgtt.

Triggered by igt gem_evict_everything test.

Testcase: igt/gem_evict_everything
Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Reviewed-by: Chris Wilson <chris@cris-wilsonc.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2014-09-19 14:41:16 +02:00
Chris Wilson d23db88c3a drm/i915: Prevent negative relocation deltas from wrapping
This is pure evil. Userspace, I'm looking at you SNA, repacks batch
buffers on the fly after generation as they are being passed to the
kernel for execution. These batches also contain self-referenced
relocations as a single buffer encompasses the state commands, kernels,
vertices and sampler. During generation the buffers are placed at known
offsets within the full batch, and then the relocation deltas (as passed
to the kernel) are tweaked as the batch is repacked into a smaller buffer.
This means that userspace is passing negative relocations deltas, which
subsequently wrap to large values if the batch is at a low address. The
GPU hangs when it then tries to use the large value as a base for its
address offsets, rather than wrapping back to the real value (as one
would hope). As the GPU uses positive offsets from the base, we can
treat the relocation address as the minimum address read by the GPU.
For the upper bound, we trust that userspace will not read beyond the
end of the buffer.

So, how do we fix negative relocations from wrapping? We can either
check that every relocation looks valid when we write it, and then
position each object such that we prevent the offset wraparound, or we
just special-case the self-referential behaviour of SNA and force all
batches to be above 256k. Daniel prefers the latter approach.

This fixes a GPU hang when it tries to use an address (relocation +
offset) greater than the GTT size. The issue would occur quite easily
with full-ppgtt as each fd gets its own VM space, so low offsets would
often be handed out. However, with the rearrangement of the low GTT due
to capturing the BIOS framebuffer, it is already affecting kernels 3.15
onwards. I think only IVB+ is susceptible to this bug, but the workaround
should only kick in rarely, so it seems sensible to always apply it.

v3: Use a bias for batch buffers to prevent small negative delta relocations
from wrapping.

v4 from Daniel:
- s/BIAS/BATCH_OFFSET_BIAS/
- Extract eb_vma_misplaced/i915_vma_misplaced since the conditions
  were growing rather cumbersome.
- Add a comment to eb_get_batch explaining why we do this.
- Apply the batch offset bias everywhere but mention that we've only
  observed it on gen7 gpus.
- Drop PIN_OFFSET_FIX for now, that slipped in from a feature patch.

v5: Add static to eb_get_batch, spotted by 0-day tester.

Testcase: igt/gem_bad_reloc
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=78533
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> (v3)
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2014-05-27 11:18:40 +03:00
Jani Nikula 50227e1cae drm/i915: prefer struct drm_i915_private to drm_i915_private_t
Remove the rest of the references to drm_i915_private_t. No functional
changes.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
[danvet: Drop hunk in i915_cmd_parser.c]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2014-03-31 15:34:21 +02:00
Daniel Vetter 1ec9e26dda drm/i915: Consolidate binding parameters into flags
Anything more than just one bool parameter is just a pain to read,
symbolic constants are much better.

Split out from Chris' vma-binding rework patch.

v2: Undo the behaviour change in object_pin that Chris spotted.

v3: Split out misplaced hunk to handle set_cache_level errors,
spotted by Jani.

v4: Keep the current over-zealous binding logic in the execbuffer code
working with a quick hack while the overall binding code gets shuffled
around.

v5: Reorder the PIN_ flags for more natural patch splitup.

v6: Pull out the PIN_GLOBAL split-up again.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ben Widawsky <benjamin.widawsky@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2014-02-14 14:16:58 +01:00
Daniel Vetter c2c1d4912c drm/i915: Kerneldoc for i915_gem_evict.c
Request by Ben Widawsky in his review of a patch touching this code.

v2: Clarify the disdinction between evicting vmas (to free up virtual
address space) and evicting objects (to free up actual system memory).
Suggested by Ben.

Cc: Ben Widawsky <benjamin.widawsky@intel.com>
Acked-by: Ben Widawsky <benjamin.widawsky@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2014-01-29 22:19:17 +01:00
Chris Wilson 3036537dbf drm/i915: VM eviction only targets address space not physical pages
During eviction, we are only considering how to free up space within the
current address space and not concerned with freeing up physical memory.
As such we need only skip nodes that pinned in the current VM and not
globally.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Ben Widawsky <benjamin.widawsky@intel.com>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2014-01-29 21:29:40 +01:00
Daniel Vetter 0e5539b923 Merge branch 'topic/ppgtt' into drm-intel-next-queued
Because whatever.*

* This should contain a fairly long list of issues and still
unresolved resgressions, but I didn't really get a vote.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2014-01-25 21:14:57 +01:00
Chris Wilson 74e21ac2cc drm/i915: Repeat evictions whilst pageflip completions are outstanding
Since an old pageflip will keep its scanout buffer object pinned until
it has executed its unpin task on the common workqueue, we can clog up
our GGTT with stale pinned objects. As we cannot flush those workqueues
without dropping our locks, we have to resort to falling back to
userspace and telling them to repeat the operation in order to have a
chance to run our workqueues and free up the required memory. If we
fail, then we are forced to report ENOSPC back to userspace causing the
operation to fail and best-case scenario is that it introduces temporary
corruption.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Jon Bloomfield <jon.bloomfield@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2014-01-22 10:34:41 +01:00