We need to keep track of the last location we ask the hw to read up to (RING_TAIL) separately from our last write location into the ring, so that in the event of a GPU reset we do not tell the HW to proceed into a partially written request (which can happen if that request is waiting for an external signal before being executed). v2: Refactor intel_ring_reset() (Mika) Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100144 Testcase: igt/gem_exec_fence/await-hang Fixes: 821ed7df6e2a ("drm/i915: Update reset path to fix incomplete requests") Fixes: d55ac5bf97c6 ("drm/i915: Defer transfer onto execution timeline to actual hw submission") Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxx> --- drivers/gpu/drm/i915/i915_gem_request.c | 16 +++++++++--- drivers/gpu/drm/i915/i915_guc_submission.c | 4 +-- drivers/gpu/drm/i915/intel_lrc.c | 6 ++--- drivers/gpu/drm/i915/intel_ringbuffer.c | 41 ++++++++++++++++++++---------- drivers/gpu/drm/i915/intel_ringbuffer.h | 19 ++++++++++++-- 5 files changed, 59 insertions(+), 27 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c index e2ec42b2bf24..126cd13abf54 100644 --- a/drivers/gpu/drm/i915/i915_gem_request.c +++ b/drivers/gpu/drm/i915/i915_gem_request.c @@ -283,10 +283,18 @@ static void advance_ring(struct drm_i915_gem_request *request) * Note this requires that we are always called in request * completion order. */ - if (list_is_last(&request->ring_link, &request->ring->request_list)) - tail = request->ring->tail; - else + if (list_is_last(&request->ring_link, &request->ring->request_list)) { + /* We may race here with execlists resubmitting this request + * as we retire it. The resubmission will move the ring->tail + * forwards (to request->wa_tail). We either read the + * current value that was written to hw, or the value that + * is just about to be. Either works, if we miss the last two + * noops - they are safe to be replayed on a reset. + */ + tail = READ_ONCE(request->ring->tail); + } else { tail = request->postfix; + } list_del(&request->ring_link); request->ring->head = tail; @@ -651,7 +659,7 @@ i915_gem_request_alloc(struct intel_engine_cs *engine, * GPU processing the request, we never over-estimate the * position of the head. */ - req->head = req->ring->tail; + req->head = req->ring->emit; /* Check that we didn't interrupt ourselves with a new request */ GEM_BUG_ON(req->timeline->seqno != req->fence.seqno); diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c index 1642fff9cf13..ab5140ba108d 100644 --- a/drivers/gpu/drm/i915/i915_guc_submission.c +++ b/drivers/gpu/drm/i915/i915_guc_submission.c @@ -480,9 +480,7 @@ static void guc_wq_item_append(struct i915_guc_client *client, GEM_BUG_ON(freespace < wqi_size); /* The GuC firmware wants the tail index in QWords, not bytes */ - tail = rq->tail; - assert_ring_tail_valid(rq->ring, rq->tail); - tail >>= 3; + tail = intel_ring_set_tail(rq->ring, rq->tail) >> 3; GEM_BUG_ON(tail > WQ_RING_TAIL_MAX); /* For now workqueue item is 4 DWs; workqueue buffer is 2 pages. So we diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c index 7df278fe492e..13057a37390b 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -326,8 +326,7 @@ static u64 execlists_update_context(struct drm_i915_gem_request *rq) rq->ctx->ppgtt ?: rq->i915->mm.aliasing_ppgtt; u32 *reg_state = ce->lrc_reg_state; - assert_ring_tail_valid(rq->ring, rq->tail); - reg_state[CTX_RING_TAIL+1] = rq->tail; + reg_state[CTX_RING_TAIL+1] = intel_ring_set_tail(rq->ring, rq->tail); /* True 32b PPGTT with dynamic page allocation: update PDP * registers and point the unallocated PDPs to scratch page. @@ -2054,8 +2053,7 @@ void intel_lr_context_resume(struct drm_i915_private *dev_priv) ce->state->obj->mm.dirty = true; i915_gem_object_unpin_map(ce->state->obj); - ce->ring->head = ce->ring->tail = 0; - intel_ring_update_space(ce->ring); + intel_ring_reset(ce->ring, 0); } } } diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c index 32afac6c754f..227dfcf1764e 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -49,7 +49,7 @@ static int __intel_ring_space(int head, int tail, int size) void intel_ring_update_space(struct intel_ring *ring) { - ring->space = __intel_ring_space(ring->head, ring->tail, ring->size); + ring->space = __intel_ring_space(ring->head, ring->emit, ring->size); } static int @@ -774,8 +774,8 @@ static void i9xx_submit_request(struct drm_i915_gem_request *request) i915_gem_request_submit(request); - assert_ring_tail_valid(request->ring, request->tail); - I915_WRITE_TAIL(request->engine, request->tail); + I915_WRITE_TAIL(request->engine, + intel_ring_set_tail(request->ring, request->tail)); } static void i9xx_emit_breadcrumb(struct drm_i915_gem_request *req, u32 *cs) @@ -1319,11 +1319,23 @@ int intel_ring_pin(struct intel_ring *ring, return PTR_ERR(addr); } +void intel_ring_reset(struct intel_ring *ring, u32 tail) +{ + GEM_BUG_ON(!list_empty(&ring->request_list)); + ring->tail = tail; + ring->head = tail; + ring->emit = tail; + intel_ring_update_space(ring); +} + void intel_ring_unpin(struct intel_ring *ring) { GEM_BUG_ON(!ring->vma); GEM_BUG_ON(!ring->vaddr); + /* Discard any unused bytes beyond that submitted to hw. */ + intel_ring_reset(ring, ring->tail); + if (i915_vma_is_map_and_fenceable(ring->vma)) i915_vma_unpin_iomap(ring->vma); else @@ -1555,8 +1567,9 @@ void intel_legacy_submission_resume(struct drm_i915_private *dev_priv) struct intel_engine_cs *engine; enum intel_engine_id id; + /* Restart from the beginning of the rings for convenience */ for_each_engine(engine, dev_priv, id) - engine->buffer->head = engine->buffer->tail; + intel_ring_reset(engine->buffer, 0); } static int ring_request_alloc(struct drm_i915_gem_request *request) @@ -1609,7 +1622,7 @@ static int wait_for_space(struct drm_i915_gem_request *req, int bytes) unsigned space; /* Would completion of this request free enough space? */ - space = __intel_ring_space(target->postfix, ring->tail, + space = __intel_ring_space(target->postfix, ring->emit, ring->size); if (space >= bytes) break; @@ -1634,8 +1647,8 @@ static int wait_for_space(struct drm_i915_gem_request *req, int bytes) u32 *intel_ring_begin(struct drm_i915_gem_request *req, int num_dwords) { struct intel_ring *ring = req->ring; - int remain_actual = ring->size - ring->tail; - int remain_usable = ring->effective_size - ring->tail; + int remain_actual = ring->size - ring->emit; + int remain_usable = ring->effective_size - ring->emit; int bytes = num_dwords * sizeof(u32); int total_bytes, wait_bytes; bool need_wrap = false; @@ -1671,17 +1684,17 @@ u32 *intel_ring_begin(struct drm_i915_gem_request *req, int num_dwords) if (unlikely(need_wrap)) { GEM_BUG_ON(remain_actual > ring->space); - GEM_BUG_ON(ring->tail + remain_actual > ring->size); + GEM_BUG_ON(ring->emit + remain_actual > ring->size); /* Fill the tail with MI_NOOP */ - memset(ring->vaddr + ring->tail, 0, remain_actual); - ring->tail = 0; + memset(ring->vaddr + ring->emit, 0, remain_actual); + ring->emit = 0; ring->space -= remain_actual; } - GEM_BUG_ON(ring->tail > ring->size - bytes); - cs = ring->vaddr + ring->tail; - ring->tail += bytes; + GEM_BUG_ON(ring->emit > ring->size - bytes); + cs = ring->vaddr + ring->emit; + ring->emit += bytes; ring->space -= bytes; GEM_BUG_ON(ring->space < 0); @@ -1692,7 +1705,7 @@ u32 *intel_ring_begin(struct drm_i915_gem_request *req, int num_dwords) int intel_ring_cacheline_align(struct drm_i915_gem_request *req) { int num_dwords = - (req->ring->tail & (CACHELINE_BYTES - 1)) / sizeof(uint32_t); + (req->ring->emit & (CACHELINE_BYTES - 1)) / sizeof(uint32_t); u32 *cs; if (num_dwords == 0) diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h index 00d36aa4e26d..96710b616efb 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.h +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h @@ -143,6 +143,7 @@ struct intel_ring { u32 head; u32 tail; + u32 emit; int space; int size; @@ -494,6 +495,8 @@ intel_engine_create_ring(struct intel_engine_cs *engine, int size); int intel_ring_pin(struct intel_ring *ring, struct drm_i915_private *i915, unsigned int offset_bias); +void intel_ring_reset(struct intel_ring *ring, u32 tail); +void intel_ring_update_space(struct intel_ring *ring); void intel_ring_unpin(struct intel_ring *ring); void intel_ring_free(struct intel_ring *ring); @@ -517,7 +520,7 @@ intel_ring_advance(struct drm_i915_gem_request *req, u32 *cs) * reserved for the command packet (i.e. the value passed to * intel_ring_begin()). */ - GEM_BUG_ON((req->ring->vaddr + req->ring->tail) != cs); + GEM_BUG_ON((req->ring->vaddr + req->ring->emit) != cs); } static inline u32 @@ -546,7 +549,19 @@ assert_ring_tail_valid(const struct intel_ring *ring, unsigned int tail) GEM_BUG_ON(tail >= ring->size); } -void intel_ring_update_space(struct intel_ring *ring); +static inline unsigned int +intel_ring_set_tail(struct intel_ring *ring, unsigned int tail) +{ + /* Whilst writes to the tail are strictly order, there is no + * serialisation between readers and the writers. The tail may be + * read by i915_gem_request_retire() just as it is being updated + * by execlists, as although the breadcrumb is complete, the context + * switch hasn't been seen. + */ + assert_ring_tail_valid(ring, tail); + ring->tail = tail; + return tail; +} void intel_engine_init_global_seqno(struct intel_engine_cs *engine, u32 seqno); -- 2.11.0 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
