In our ABI we have defined I915_ENGINE_CLASS_INVALID_NONE and
I915_ENGINE_CLASS_INVALID_VIRTUAL as negative values which creates
implicit coupling with type widths used in, also ABI, struct
i915_engine_class_instance.
One place where we export engine->uabi_class
I915_ENGINE_CLASS_INVALID_VIRTUAL is from our our tracepoints. Because the
type of the former is u8 in contrast to u16 defined in the ABI, 254 will
be returned instead of 65534 which userspace would legitimately expect.
Another place is I915_CONTEXT_PARAM_ENGINES.
Therefore we need to align the type used to store engine ABI class and
instance.
v2:
* Update the commit message mentioning get_engines and cc stable.
(Chris)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Fixes: 6d06779e86 ("drm/i915: Load balancing across a virtual engine")
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: <stable@vger.kernel.org> # v5.3+
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200116134508.25211-1-tvrtko.ursulin@linux.intel.com
(cherry picked from commit 0b3bd0cdc3)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
This reverts
67c97fb79a ("dma-buf: add reservation_object_fences helper")
dd7a7d1ff2 ("drm/i915: use new reservation_object_fences helper")
0e1d8083bd ("dma-buf: further relax reservation_object_add_shared_fence")
5d344f58da ("dma-buf: nuke reservation_object seq number")
The scenario that defeats simply grabbing a set of shared/exclusive
fences and using them blissfully under RCU is that any of those fences
may be reallocated by a SLAB_TYPESAFE_BY_RCU fence slab cache. In this
scenario, while keeping the rcu_read_lock we need to establish that no
fence was changed in the dma_resv after a read (or full) memory barrier.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190814182401.25009-1-chris@chris-wilson.co.uk
