[Intel-gfx] [PATCH 22/46] drm/i915/guc: Implement multi-lrc submission

Matthew Brost
2021-08-03T22:12:40Z

Implement multi-lrc submission via a single workqueue entry and single
H2G. The workqueue entry contains an updated tail value for each
request, of all the contexts in the multi-lrc submission, and updates
these values simultaneously. As such, the tasklet and bypass path have
been updated to coalesce requests into a single submission.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h | 6 +-
.../gpu/drm/i915/gt/uc/intel_guc_submission.c | 224 +++++++++++++++++-
drivers/gpu/drm/i915/i915_request.h | 8 +
3 files changed, 223 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h b/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
index e08fbd40281c..6910a0cdb8c8 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
@@ -64,12 +64,14 @@
#define WQ_TYPE_PSEUDO (0x2 << WQ_TYPE_SHIFT)
#define WQ_TYPE_INORDER (0x3 << WQ_TYPE_SHIFT)
#define WQ_TYPE_NOOP (0x4 << WQ_TYPE_SHIFT)
-#define WQ_TARGET_SHIFT 10
+#define WQ_TYPE_MULTI_LRC (0x5 << WQ_TYPE_SHIFT)
+#define WQ_TARGET_SHIFT 8
#define WQ_LEN_SHIFT 16
#define WQ_NO_WCFLUSH_WAIT (1 << 27)
#define WQ_PRESENT_WORKLOAD (1 << 28)

-#define WQ_RING_TAIL_SHIFT 20
+#define WQ_GUC_ID_SHIFT 0
+#define WQ_RING_TAIL_SHIFT 18
#define WQ_RING_TAIL_MAX 0x7FF /* 2^11 QWords */
#define WQ_RING_TAIL_MASK (WQ_RING_TAIL_MAX << WQ_RING_TAIL_SHIFT)

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 850edeff9230..d1d4a1e59e8d 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -493,6 +493,29 @@ __get_process_desc(struct intel_context *ce)
LRC_STATE_OFFSET) / sizeof(u32)));
}

+static inline u32 *get_wq_pointer(struct guc_process_desc *desc,
+ struct intel_context *ce,
+ u32 wqi_size)
+{
+ /*
+ * Check for space in work queue. Caching a value of head pointer in
+ * intel_context structure in order reduce the number accesses to shared
+ * GPU memory which may be across a PCIe bus.
+ */
+#define AVAILABLE_SPACE \
+ CIRC_SPACE(ce->guc_wqi_tail, ce->guc_wqi_head, GUC_WQ_SIZE)
+ if (wqi_size > AVAILABLE_SPACE) {
+ ce->guc_wqi_head = READ_ONCE(desc->head);
+
+ if (wqi_size > AVAILABLE_SPACE)
+ return NULL;
+ }
+#undef AVAILABLE_SPACE
+
+ return ((u32 *)__get_process_desc(ce)) +
+ ((WQ_OFFSET + ce->guc_wqi_tail) / sizeof(u32));
+}
+
static u32 __get_lrc_desc_offset(struct intel_guc *guc, int index)
{
GEM_BUG_ON(index >= guc->lrcd_reg.max_idx);
@@ -643,7 +666,7 @@ static inline bool request_has_no_guc_id(struct i915_request *rq)
static int __guc_add_request(struct intel_guc *guc, struct i915_request *rq)
{
int err = 0;
- struct intel_context *ce = rq->context;
+ struct intel_context *ce = request_to_scheduling_context(rq);
u32 action[3];
int len = 0;
u32 g2h_len_dw = 0;
@@ -697,6 +720,18 @@ static int __guc_add_request(struct intel_guc *guc, struct i915_request *rq)
trace_intel_context_sched_enable(ce);
atomic_inc(&guc->outstanding_submission_g2h);
set_context_enabled(ce);
+
+ /*
+ * Without multi-lrc KMD does the submission step (moving the
+ * lrc tail) so enabling scheduling is sufficient to submit the
+ * context. This isn't the case in multi-lrc submission as the
+ * GuC needs to move the tails, hence the need for another H2G
+ * to submit a multi-lrc context after enabling scheduling.
+ */
+ if (intel_context_is_parent(ce)) {
+ action[0] = INTEL_GUC_ACTION_SCHED_CONTEXT;
+ err = intel_guc_send_nb(guc, action, len - 1, 0);
+ }
} else if (!enabled) {
clr_context_pending_enable(ce);
intel_context_put(ce);
@@ -783,6 +818,132 @@ static inline int rq_prio(const struct i915_request *rq)
return rq->sched.attr.priority;
}

+static inline bool is_multi_lrc_rq(struct i915_request *rq)
+{
+ return intel_context_is_child(rq->context) ||
+ intel_context_is_parent(rq->context);
+}
+
+/*
+ * Multi-lrc requests are not submitted to the GuC until all requests in
+ * the set are ready. With the exception of the last request in the set,
+ * submitting a multi-lrc request is therefore just a status update on
+ * the driver-side and can be safely merged with other requests. When the
+ * last multi-lrc request in a set is detected, we break out of the
+ * submission loop and submit the whole set, thus we never attempt to
+ * merge that one with othe requests.
+ */
+static inline bool can_merge_rq(struct i915_request *rq,
+ struct i915_request *last)
+{
+ return is_multi_lrc_rq(last) || rq->context == last->context;
+}
+
+static inline u32 wq_space_until_wrap(struct intel_context *ce)
+{
+ return (GUC_WQ_SIZE - ce->guc_wqi_tail);
+}
+
+static inline void write_wqi(struct guc_process_desc *desc,
+ struct intel_context *ce,
+ u32 wqi_size)
+{
+ ce->guc_wqi_tail = (ce->guc_wqi_tail + wqi_size) & (GUC_WQ_SIZE - 1);
+ WRITE_ONCE(desc->tail, ce->guc_wqi_tail);
+}
+
+static inline int guc_wq_noop_append(struct intel_context *ce)
+{
+ struct guc_process_desc *desc = __get_process_desc(ce);
+ u32 *wqi = get_wq_pointer(desc, ce, wq_space_until_wrap(ce));
+
+ if (!wqi)
+ return -EBUSY;
+
+ *wqi = WQ_TYPE_NOOP |
+ ((wq_space_until_wrap(ce) / sizeof(u32) - 1) << WQ_LEN_SHIFT);
+ ce->guc_wqi_tail = 0;
+
+ return 0;
+}
+
+static int __guc_wq_item_append(struct i915_request *rq)
+{
+ struct intel_context *ce = request_to_scheduling_context(rq);
+ struct intel_context *child;
+ struct guc_process_desc *desc = __get_process_desc(ce);
+ unsigned int wqi_size = (ce->guc_number_children + 4) *
+ sizeof(u32);
+ u32 *wqi;
+ int ret;
+
+ /* Ensure context is in correct state updating work queue */
+ GEM_BUG_ON(ce->guc_num_rq_submit_no_id);
+ GEM_BUG_ON(request_has_no_guc_id(rq));
+ GEM_BUG_ON(!atomic_read(&ce->guc_id_ref));
+ GEM_BUG_ON(context_guc_id_invalid(ce));
+ GEM_BUG_ON(context_pending_disable(ce));
+ GEM_BUG_ON(context_wait_for_deregister_to_register(ce));
+
+ /* Insert NOOP if this work queue item will wrap the tail pointer. */
+ if (wqi_size > wq_space_until_wrap(ce)) {
+ ret = guc_wq_noop_append(ce);
+ if (ret)
+ return ret;
+ }
+
+ wqi = get_wq_pointer(desc, ce, wqi_size);
+ if (!wqi)
+ return -EBUSY;
+
+ *wqi++ = WQ_TYPE_MULTI_LRC |
+ ((wqi_size / sizeof(u32) - 1) << WQ_LEN_SHIFT);
+ *wqi++ = ce->lrc.lrca;
+ *wqi++ = (ce->guc_id << WQ_GUC_ID_SHIFT) |
+ ((ce->ring->tail / sizeof(u64)) << WQ_RING_TAIL_SHIFT);
+ *wqi++ = 0; /* fence_id */
+ for_each_child(ce, child)
+ *wqi++ = child->ring->tail / sizeof(u64);
+
+ write_wqi(desc, ce, wqi_size);
+
+ return 0;
+}
+
+static int gse_wq_item_append(struct guc_submit_engine *gse,
+ struct i915_request *rq)
+{
+ struct intel_context *ce = request_to_scheduling_context(rq);
+ int ret = 0;
+
+ if (likely(!intel_context_is_banned(ce))) {
+ ret = __guc_wq_item_append(rq);
+
+ if (unlikely(ret == -EBUSY)) {
+ gse->stalled_rq = rq;
+ gse->submission_stall_reason = STALL_MOVE_LRC_TAIL;
+ }
+ }
+
+ return ret;
+}
+
+static inline bool multi_lrc_submit(struct i915_request *rq)
+{
+ struct intel_context *ce = request_to_scheduling_context(rq);
+
+ intel_ring_set_tail(rq->ring, rq->tail);
+
+ /*
+ * We expect the front end (execbuf IOCTL) to set this flag on the last
+ * request generated from a multi-BB submission. This indicates to the
+ * backend (GuC interface) that we should submit this context thus
+ * submitting all the requests generated in parallel.
+ */
+ return test_bit(I915_FENCE_FLAG_SUBMIT_PARALLEL, &rq->fence.flags) ||
+ intel_context_is_banned(ce);
+}
+
static void kick_retire_wq(struct guc_submit_engine *gse)
{
queue_work(system_unbound_wq, &gse->retire_worker);
@@ -826,7 +987,7 @@ static int gse_dequeue_one_context(struct guc_submit_engine *gse)
struct i915_request *rq, *rn;

priolist_for_each_request_consume(rq, rn, p) {
- if (last && rq->context != last->context)
+ if (last && !can_merge_rq(rq, last))
goto done;

list_del_init(&rq->sched.link);
@@ -835,7 +996,22 @@ static int gse_dequeue_one_context(struct guc_submit_engine *gse)

trace_i915_request_in(rq, 0);
last = rq;
- submit = true;
+
+ if (is_multi_lrc_rq(rq)) {
+ /*
+ * We need to coalesce all multi-lrc
+ * requests in a relationship into a
+ * single H2G. We are guaranteed that
+ * all of these requests will be
+ * submitted sequentially.
+ */
+ if (multi_lrc_submit(rq)) {
+ submit = true;
+ goto done;
+ }
+ } else {
+ submit = true;
+ }
}

rb_erase_cached(&p->node, &sched_engine->queue);
@@ -845,7 +1021,7 @@ static int gse_dequeue_one_context(struct guc_submit_engine *gse)

done:
if (submit) {
- struct intel_context *ce = last->context;
+ struct intel_context *ce = request_to_scheduling_context(last);

if (ce->guc_num_rq_submit_no_id) {
ret = tasklet_pin_guc_id(gse, last);
@@ -867,7 +1043,17 @@ static int gse_dequeue_one_context(struct guc_submit_engine *gse)
}

move_lrc_tail:
- guc_set_lrc_tail(last);
+ if (is_multi_lrc_rq(last)) {
+ ret = gse_wq_item_append(gse, last);
+ if (ret == -EBUSY) {
+ goto schedule_tasklet;
+ } else if (ret != 0) {
+ GEM_WARN_ON(ret); /* Unexpected */
+ goto deadlk;
+ }
+ } else {
+ guc_set_lrc_tail(last);
+ }

add_request:
ret = gse_add_request(gse, last);
@@ -1575,14 +1761,22 @@ static bool need_tasklet(struct guc_submit_engine *gse, struct intel_context *ce
static int gse_bypass_tasklet_submit(struct guc_submit_engine *gse,
struct i915_request *rq)
{
- int ret;
+ int ret = 0;

__i915_request_submit(rq);

trace_i915_request_in(rq, 0);

- guc_set_lrc_tail(rq);
- ret = gse_add_request(gse, rq);
+ if (is_multi_lrc_rq(rq)) {
+ if (multi_lrc_submit(rq)) {
+ ret = gse_wq_item_append(gse, rq);
+ if (!ret)
+ ret = gse_add_request(gse, rq);
+ }
+ } else {
+ guc_set_lrc_tail(rq);
+ ret = gse_add_request(gse, rq);
+ }

if (unlikely(ret == -EPIPE))
disable_submission(gse->sched_engine.private_data);
@@ -1599,7 +1793,7 @@ static void guc_submit_request(struct i915_request *rq)
/* Will be called from irq-context when using foreign fences. */
spin_lock_irqsave(&sched_engine->lock, flags);

- if (need_tasklet(gse, rq->context))
+ if (need_tasklet(gse, request_to_scheduling_context(rq)))
queue_request(sched_engine, rq, rq_prio(rq));
else if (gse_bypass_tasklet_submit(gse, rq) == -EBUSY)
kick_tasklet(gse);
@@ -2988,9 +3182,10 @@ static inline bool new_guc_prio_higher(u8 old_guc_prio, u8 new_guc_prio)

static void add_to_context(struct i915_request *rq)
{
- struct intel_context *ce = rq->context;
+ struct intel_context *ce = request_to_scheduling_context(rq);
u8 new_guc_prio = map_i915_prio_to_guc_prio(rq_prio(rq));

+ GEM_BUG_ON(intel_context_is_child(ce));
GEM_BUG_ON(rq->guc_prio == GUC_PRIO_FINI);

spin_lock(&ce->guc_active.lock);
@@ -3026,7 +3221,9 @@ static void guc_prio_fini(struct i915_request *rq, struct intel_context *ce)

static void remove_from_context(struct i915_request *rq)
{
- struct intel_context *ce = rq->context;
+ struct intel_context *ce = request_to_scheduling_context(rq);
+
+ GEM_BUG_ON(intel_context_is_child(ce));

spin_lock_irq(&ce->guc_active.lock);

@@ -3231,7 +3428,8 @@ static int tasklet_pin_guc_id(struct guc_submit_engine *gse,
GEM_BUG_ON(gse->total_num_rq_with_no_guc_id < 0);

list_for_each_entry_reverse(rq, &ce->guc_active.requests, sched.link)
- if (request_has_no_guc_id(rq)) {
+ if (request_has_no_guc_id(rq) &&
+ request_to_scheduling_context(rq) == ce) {
--ce->guc_num_rq_submit_no_id;
clear_bit(I915_FENCE_FLAG_GUC_ID_NOT_PINNED,
&rq->fence.flags);
@@ -3551,7 +3749,7 @@ static void guc_bump_inflight_request_prio(struct i915_request *rq,

static void guc_retire_inflight_request_prio(struct i915_request *rq)
{
- struct intel_context *ce = rq->context;
+ struct intel_context *ce = request_to_scheduling_context(rq);

spin_lock(&ce->guc_active.lock);
guc_prio_fini(rq, ce);
diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
index 807f76750cf4..d6d5bf0a5eb5 100644
--- a/drivers/gpu/drm/i915/i915_request.h
+++ b/drivers/gpu/drm/i915/i915_request.h
@@ -145,6 +145,14 @@ enum {
* tasklet that the guc_id isn't pinned.
*/
I915_FENCE_FLAG_GUC_ID_NOT_PINNED,
+
+ /*
+ * I915_FENCE_FLAG_SUBMIT_PARALLEL - request with a context in a
+ * parent-child relationship (parallel submission, multi-lrc) should
+ * trigger a submission to the GuC rather than just moving the context
+ * tail.
+ */
+ I915_FENCE_FLAG_SUBMIT_PARALLEL,
};

/**
--
2.28.0