On 10/13/2021 13:42, Matthew Brost wrote:
If an error occurs in the front end when multi-lrc requests are getting
generated we need to skip these in the backend but we still need to
emit the breadcrumbs seqno. An issues arises because with multi-lrc
breadcrumbs there is a handshake between the parent and children to make
forward progress. If all the requests are not present this handshake
doesn't work. To work around this, if multi-lrc request has an error we
skip the handshake but still emit the breadcrumbs seqno.
v2:
(John Harrison)
- Add comment explaining the skipping of the handshake logic
- Fix typos in the commit message
v3:
(John Harrison)
- Fix up some comments about the math to NOP the ring
Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
Reviewed-by: John Harrison <John.C.Harrison@xxxxxxxxx>
---
.../gpu/drm/i915/gt/uc/intel_guc_submission.c | 69 ++++++++++++++++++-
1 file changed, 66 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
index bfafe996e2d2..80d8ce68ff59 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -4076,8 +4076,8 @@ static int emit_bb_start_child_no_preempt_mid_batch(struct i915_request *rq,
}
static u32 *
-emit_fini_breadcrumb_parent_no_preempt_mid_batch(struct i915_request *rq,
- u32 *cs)
+__emit_fini_breadcrumb_parent_no_preempt_mid_batch(struct i915_request *rq,
+ u32 *cs)
{
struct intel_context *ce = rq->context;
u8 i;
@@ -4105,6 +4105,45 @@ emit_fini_breadcrumb_parent_no_preempt_mid_batch(struct i915_request *rq,
get_children_go_addr(ce),
0);
+ return cs;
+}
+
+/*
+ * If this true, a submission of multi-lrc requests had an error and the
+ * requests need to be skipped. The front end (execuf IOCTL) should've called
+ * i915_request_skip which squashes the BB but we still need to emit the fini
+ * breadrcrumbs seqno write. At this point we don't know how many of the
+ * requests in the multi-lrc submission were generated so we can't do the
+ * handshake between the parent and children (e.g. if 4 requests should be
+ * generated but 2nd hit an error only 1 would be seen by the GuC backend).
+ * Simply skip the handshake, but still emit the breadcrumbd seqno, if an error
+ * has occurred on any of the requests in submission / relationship.
+ */
+static inline bool skip_handshake(struct i915_request *rq)
+{
+ return test_bit(I915_FENCE_FLAG_SKIP_PARALLEL, &rq->fence.flags);
+}
+
+static u32 *
+emit_fini_breadcrumb_parent_no_preempt_mid_batch(struct i915_request *rq,
+ u32 *cs)
+{
+ struct intel_context *ce = rq->context;
+
+ GEM_BUG_ON(!intel_context_is_parent(ce));
+
+ if (unlikely(skip_handshake(rq))) {
+ /*
+ * NOP everything in __emit_fini_breadcrumb_parent_no_preempt_mid_batch,
+ * the -6 comes from the length of the emits below.
+ */
+ memset(cs, 0, sizeof(u32) *
+ (ce->engine->emit_fini_breadcrumb_dw - 6));
+ cs += ce->engine->emit_fini_breadcrumb_dw - 6;
+ } else {
+ cs = __emit_fini_breadcrumb_parent_no_preempt_mid_batch(rq, cs);
+ }
+
/* Emit fini breadcrumb */
cs = gen8_emit_ggtt_write(cs,
rq->fence.seqno,
@@ -4121,7 +4160,8 @@ emit_fini_breadcrumb_parent_no_preempt_mid_batch(struct i915_request *rq,
}
static u32 *
-emit_fini_breadcrumb_child_no_preempt_mid_batch(struct i915_request *rq, u32 *cs)
+__emit_fini_breadcrumb_child_no_preempt_mid_batch(struct i915_request *rq,
+ u32 *cs)
{
struct intel_context *ce = rq->context;
struct intel_context *parent = intel_context_to_parent(ce);
@@ -4148,6 +4188,29 @@ emit_fini_breadcrumb_child_no_preempt_mid_batch(struct i915_request *rq, u32 *cs
*cs++ = get_children_go_addr(parent);
*cs++ = 0;
+ return cs;
+}
+
+static u32 *
+emit_fini_breadcrumb_child_no_preempt_mid_batch(struct i915_request *rq,
+ u32 *cs)
+{
+ struct intel_context *ce = rq->context;
+
+ GEM_BUG_ON(!intel_context_is_child(ce));
+
+ if (unlikely(skip_handshake(rq))) {
+ /*
+ * NOP everything in __emit_fini_breadcrumb_child_no_preempt_mid_batch,
+ * the -6 comes from the length of the emits below.
+ */
+ memset(cs, 0, sizeof(u32) *
+ (ce->engine->emit_fini_breadcrumb_dw - 6));
+ cs += ce->engine->emit_fini_breadcrumb_dw - 6;
+ } else {
+ cs = __emit_fini_breadcrumb_child_no_preempt_mid_batch(rq, cs);
+ }
+
/* Emit fini breadcrumb */
cs = gen8_emit_ggtt_write(cs,
rq->fence.seqno,
