On 08/06/2018 18:25, Chris Wilson wrote:
The HW only accepts offsets within ring->size, and fails peculiarly if
the RING_HEAD or RING_TAIL is set to ring->size. Therefore whenever we
set ring->head/ring->tail we want to make sure it is within value (using
intel_ring_wrap()).
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
Cc: Matthew Auld <matthew.william.auld@xxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/intel_ringbuffer.c | 5 +++++
drivers/gpu/drm/i915/intel_ringbuffer.h | 12 ++++++++++++
2 files changed, 17 insertions(+)
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 6ac3b65373fe..9fac0e0f078e 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -496,6 +496,10 @@ static int init_ring_common(struct intel_engine_cs *engine)
DRM_DEBUG_DRIVER("%s initialization failed [head=%08x], fudging\n",
engine->name, I915_READ_HEAD(engine));
+ /* Check that the ring offsets point within the ring! */
+ GEM_BUG_ON(!intel_ring_offset_valid(ring, ring->head));
+ GEM_BUG_ON(!intel_ring_offset_valid(ring, ring->tail));
+
intel_ring_update_space(ring);
I915_WRITE_HEAD(engine, ring->head);
I915_WRITE_TAIL(engine, ring->tail);
@@ -1064,6 +1068,7 @@ int intel_ring_pin(struct intel_ring *ring,
void intel_ring_reset(struct intel_ring *ring, u32 tail)
{
+ tail = intel_ring_wrap(ring, tail);
ring->tail = tail;
ring->head = tail;
ring->emit = tail;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index b44c67849749..1d8140ac2016 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -805,6 +805,18 @@ static inline u32 intel_ring_wrap(const struct intel_ring *ring, u32 pos)
return pos & (ring->size - 1);
}
+static inline bool
+intel_ring_offset_valid(const struct intel_ring *ring, u32 pos)
+{
+ if (pos & -ring->size) /* must be strictly within the ring */
+ return false;
+
+ if (!IS_ALIGNED(pos, 8)) /* must be qword aligned */
+ return false;
+
+ return true;
+}
Looks like we have assert_ring_tail_valid and intel_ring_set_tail
already in the tree. So could just use the latter in intel_ring_reset if
needed. But also since intel_ring_reset is only setting the tail to
either zero or existing ring->tail it sounds like the check would be
better placed where the tail advances?
Regards,
Tvrtko
+
static inline u32 intel_ring_offset(const struct i915_request *rq, void *addr)
{
/* Don't write ring->size (equivalent to 0) as that hangs some GPUs. */
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