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()).
v2: Double check execlists as well
v3: Remove redundancy with assert_ring_tail_valid()
v4: Just assert in intel_ring_reset() rather than be over-defensive.
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>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> #v2
---
drivers/gpu/drm/i915/intel_lrc.c | 6 ++++--
drivers/gpu/drm/i915/intel_ringbuffer.c | 6 ++++++
drivers/gpu/drm/i915/intel_ringbuffer.h | 20 ++++++++++++++------
3 files changed, 24 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 091e28f0e024..3e008adf5a01 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1413,6 +1413,7 @@ __execlists_context_pin(struct intel_engine_cs *engine,
ce->lrc_reg_state = vaddr + LRC_STATE_PN * PAGE_SIZE;
ce->lrc_reg_state[CTX_RING_BUFFER_START+1] =
i915_ggtt_offset(ce->ring->vma);
+ GEM_BUG_ON(!intel_ring_offset_valid(ce->ring, ce->ring->head));
ce->lrc_reg_state[CTX_RING_HEAD+1] = ce->ring->head;
ce->state->obj->pin_global++;
@@ -2001,9 +2002,10 @@ static void execlists_reset(struct intel_engine_cs *engine,
/* Move the RING_HEAD onto the breadcrumb, past the hanging batch */
regs[CTX_RING_BUFFER_START + 1] = i915_ggtt_offset(request->ring->vma);
- regs[CTX_RING_HEAD + 1] = request->postfix;
- request->ring->head = request->postfix;
+ request->ring->head = intel_ring_wrap(request->ring, request->postfix);
+ regs[CTX_RING_HEAD + 1] = request->ring->head;
+
intel_ring_update_space(request->ring);
/* Reset WaIdleLiteRestore:bdw,skl as well */
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 3af6daa75f51..0189ef1c78c2 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 +1068,8 @@ int intel_ring_pin(struct intel_ring *ring,
void intel_ring_reset(struct intel_ring *ring, u32 tail)
{
+ GEM_BUG_ON(!intel_ring_offset_valid(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..e9494557aaa1 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -805,6 +805,19 @@ 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,
+ unsigned int 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;
+}
+
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. */
@@ -816,12 +829,7 @@ static inline u32 intel_ring_offset(const struct i915_request *rq, void *addr)
static inline void
assert_ring_tail_valid(const struct intel_ring *ring, unsigned int tail)
{
- /* We could combine these into a single tail operation, but keeping
- * them as seperate tests will help identify the cause should one
- * ever fire.
- */
- GEM_BUG_ON(!IS_ALIGNED(tail, 8));
- GEM_BUG_ON(tail >= ring->size);
+ GEM_BUG_ON(!intel_ring_offset_valid(ring, tail));
/*
* "Ring Buffer Use"
--
2.17.1
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