It's possible for invalidate_range_start mmu notifier callback to race
against userptr object release. If the gem object was released prior to
obtaining the spinlock in invalidate_range_start we're hitting null
pointer dereference.
Testcase: igt/gem_userptr_blits/stress-mm-invalidate-close
Testcase: igt/gem_userptr_blits/stress-mm-invalidate-close-overlap
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@vger.kernel.org
[Jani: added code comment suggested by Chris]
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
sg_alloc_table_from_pages() can build us a table with coalesced ranges which
means we need to iterate over pages and not sg table entries when releasing
page references.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: "Barbalho, Rafael" <rafael.barbalho@intel.com>
Tested-by: Rafael Barbalho <rafael.barbalho@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@vger.kernel.org
[danvet: Remove unused local variable sg.]
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
During release of the GEM object we hold the struct_mutex. As the
object may be holding onto the last reference for the task->mm,
calling mmput() may trigger exit_mmap() which close the vma
which will call drm_gem_vm_close() and attempt to reacquire
the struct_mutex. In order to avoid that recursion, we have
to defer the mmput() until after we drop the struct_mutex,
i.e. we need to schedule a worker to do the clean up. A further issue
spotted by Tvrtko was caused when we took a GTT mmapping of a userptr
buffer object. In that case, we would never call mmput as the object
would be cyclically referenced by the GTT mmapping and not freed upon
process exit - keeping the entire process mm alive after the process
task was reaped. The fix employed is to replace the mm_users/mmput()
reference handling to mm_count/mmdrop() for the shared i915_mm_struct.
INFO: task test_surfaces:1632 blocked for more than 120 seconds.
Tainted: GF O 3.14.5+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
test_surfaces D 0000000000000000 0 1632 1590 0x00000082
ffff88014914baa8 0000000000000046 0000000000000000 ffff88014914a010
0000000000012c40 0000000000012c40 ffff8800a0058210 ffff88014784b010
ffff88014914a010 ffff880037b1c820 ffff8800a0058210 ffff880037b1c824
Call Trace:
[<ffffffff81582499>] schedule+0x29/0x70
[<ffffffff815825fe>] schedule_preempt_disabled+0xe/0x10
[<ffffffff81583b93>] __mutex_lock_slowpath+0x183/0x220
[<ffffffff81583c53>] mutex_lock+0x23/0x40
[<ffffffffa005c2a3>] drm_gem_vm_close+0x33/0x70 [drm]
[<ffffffff8115a483>] remove_vma+0x33/0x70
[<ffffffff8115a5dc>] exit_mmap+0x11c/0x170
[<ffffffff8104d6eb>] mmput+0x6b/0x100
[<ffffffffa00f44b9>] i915_gem_userptr_release+0x89/0xc0 [i915]
[<ffffffffa00e6706>] i915_gem_free_object+0x126/0x250 [i915]
[<ffffffffa005c06a>] drm_gem_object_free+0x2a/0x40 [drm]
[<ffffffffa005cc32>] drm_gem_object_handle_unreference_unlocked+0xe2/0x120 [drm]
[<ffffffffa005ccd4>] drm_gem_object_release_handle+0x64/0x90 [drm]
[<ffffffff8127ffeb>] idr_for_each+0xab/0x100
[<ffffffffa005cc70>] ? drm_gem_object_handle_unreference_unlocked+0x120/0x120 [drm]
[<ffffffff81583c46>] ? mutex_lock+0x16/0x40
[<ffffffffa005c354>] drm_gem_release+0x24/0x40 [drm]
[<ffffffffa005b82b>] drm_release+0x3fb/0x480 [drm]
[<ffffffff8118d482>] __fput+0xb2/0x260
[<ffffffff8118d6de>] ____fput+0xe/0x10
[<ffffffff8106f27f>] task_work_run+0x8f/0xf0
[<ffffffff81052228>] do_exit+0x1a8/0x480
[<ffffffff81052551>] do_group_exit+0x51/0xc0
[<ffffffff810525d7>] SyS_exit_group+0x17/0x20
[<ffffffff8158e092>] system_call_fastpath+0x16/0x1b
v2: Incorporate feedback from Tvrtko and remove the unnessary mm
referencing when creating the i915_mm_struct and improve some of the
function names and comments.
Reported-by: Jacek Danecki <jacek.danecki@intel.com>
Test-case: igt/gem_userptr_blits/process-exit*
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: "Gong, Zhipeng" <zhipeng.gong@intel.com>
Cc: Jacek Danecki <jacek.danecki@intel.com>
Cc: "Ursulin, Tvrtko" <tvrtko.ursulin@intel.com>
Reviewed-by: "Ursulin, Tvrtko" <tvrtko.ursulin@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org # hold off until 3.17 ships for additional testing
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Move the code around in order to acquire and release the spinlock in the
same function and in the same block. This keeps static analysers happy
and the reader sane.
Suggested-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Whilst I strongly advise against doing so for the implicit coherency
issues between the multiple buffer objects accessing the same backing
store, it nevertheless is a valid use case, akin to mmaping the same
file multiple times.
The reason why we forbade it earlier was that our use of the interval
tree for fast invalidation upon vma changes excluded overlapping
objects. So in the case where the user wishes to create such pairs of
overlapping objects, we degrade the range invalidation to walkin the
linear list of objects associated with the mm.
A situation where overlapping objects could arise is the lax implementation
of MIT-SHM Pixmaps in the xserver. A second situation is where the user
wishes to have different access modes to a region of memory (e.g. access
through a read-only userptr buffer and through a normal userptr buffer).
v2: Compile for mmu-notifiers after tweaking
v3: Rename is_linear/has_linear
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: "Li, Victor Y" <victor.y.li@intel.com>
Cc: "Kelley, Sean V" <sean.v.kelley@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: "Gong, Zhipeng" <zhipeng.gong@intel.com>
Cc: Akash Goel <akash.goel@intel.com>
Cc: "Volkin, Bradley D" <bradley.d.volkin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
During the range invalidate, we walk the list of buffers associated with
the mmu_notifer and find the ones that overlap the range. An
optimisation is made to speed up the iteration by assuming the previous
iter is still valid whilst the tree is unmodified. This exposes a bug
when a range invalidate is triggered after we have just created the
mmu_notifier, but before attaching any buffers. In that case, we presume
we have an unmodified list and start walking from the last iter which is
NULL. Oops.
The easiest fix is then to initialise the serial of the tree to 1.
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>
Testecase: igt/gem_userptr_blts/stress-mm
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
By exporting the ability to map user address and inserting PTEs
representing their backing pages into the GTT, we can exploit UMA in order
to utilize normal application data as a texture source or even as a
render target (depending upon the capabilities of the chipset). This has
a number of uses, with zero-copy downloads to the GPU and efficient
readback making the intermixed streaming of CPU and GPU operations
fairly efficient. This ability has many widespread implications from
faster rendering of client-side software rasterisers (chromium),
mitigation of stalls due to read back (firefox) and to faster pipelining
of texture data (such as pixel buffer objects in GL or data blobs in CL).
v2: Compile with CONFIG_MMU_NOTIFIER
v3: We can sleep while performing invalidate-range, which we can utilise
to drop our page references prior to the kernel manipulating the vma
(for either discard or cloning) and so protect normal users.
v4: Only run the invalidate notifier if the range intercepts the bo.
v5: Prevent userspace from attempting to GTT mmap non-page aligned buffers
v6: Recheck after reacquire mutex for lost mmu.
v7: Fix implicit padding of ioctl struct by rounding to next 64bit boundary.
v8: Fix rebasing error after forwarding porting the back port.
v9: Limit the userptr to page aligned entries. We now expect userspace
to handle all the offset-in-page adjustments itself.
v10: Prevent vma from being copied across fork to avoid issues with cow.
v11: Drop vma behaviour changes -- locking is nigh on impossible.
Use a worker to load user pages to avoid lock inversions.
v12: Use get_task_mm()/mmput() for correct refcounting of mm.
v13: Use a worker to release the mmu_notifier to avoid lock inversion
v14: Decouple mmu_notifier from struct_mutex using a custom mmu_notifer
with its own locking and tree of objects for each mm/mmu_notifier.
v15: Prevent overlapping userptr objects, and invalidate all objects
within the mmu_notifier range
v16: Fix a typo for iterating over multiple objects in the range and
rearrange error path to destroy the mmu_notifier locklessly.
Also close a race between invalidate_range and the get_pages_worker.
v17: Close a race between get_pages_worker/invalidate_range and fresh
allocations of the same userptr range - and notice that
struct_mutex was presumed to be held when during creation it wasn't.
v18: Sigh. Fix the refactor of st_set_pages() to allocate enough memory
for the struct sg_table and to clear it before reporting an error.
v19: Always error out on read-only userptr requests as we don't have the
hardware infrastructure to support them at the moment.
v20: Refuse to implement read-only support until we have the required
infrastructure - but reserve the bit in flags for future use.
v21: use_mm() is not required for get_user_pages(). It is only meant to
be used to fix up the kernel thread's current->mm for use with
copy_user().
v22: Use sg_alloc_table_from_pages for that chunky feeling
v23: Export a function for sanity checking dma-buf rather than encode
userptr details elsewhere, and clean up comments based on
suggestions by Bradley.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: "Gong, Zhipeng" <zhipeng.gong@intel.com>
Cc: Akash Goel <akash.goel@intel.com>
Cc: "Volkin, Bradley D" <bradley.d.volkin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: Brad Volkin <bradley.d.volkin@intel.com>
[danvet: Frob ioctl allocation to pick the next one - will cause a bit
of fuss with create2 apparently, but such are the rules.]
[danvet2: oops, forgot to git add after manual patch application]
[danvet3: Appease sparse.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Michał Winiarski