/* * Copyright © 2008-2015 Intel Corporation * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice (including the next * paragraph) shall be included in all copies or substantial portions of the * Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS * IN THE SOFTWARE. * */ #include #include #include #include #include #include #include "gem/i915_gem_context.h" #include "gt/intel_context.h" #include "gt/intel_ring.h" #include "gt/intel_rps.h" #include "i915_active.h" #include "i915_drv.h" #include "i915_globals.h" #include "i915_trace.h" #include "intel_pm.h" struct execute_cb { struct list_head link; struct irq_work work; struct i915_sw_fence *fence; void (*hook)(struct i915_request *rq, struct dma_fence *signal); struct i915_request *signal; }; static struct i915_global_request { struct i915_global base; struct kmem_cache *slab_requests; struct kmem_cache *slab_execute_cbs; } global; static const char *i915_fence_get_driver_name(struct dma_fence *fence) { return dev_name(to_request(fence)->i915->drm.dev); } static const char *i915_fence_get_timeline_name(struct dma_fence *fence) { const struct i915_gem_context *ctx; /* * The timeline struct (as part of the ppgtt underneath a context) * may be freed when the request is no longer in use by the GPU. * We could extend the life of a context to beyond that of all * fences, possibly keeping the hw resource around indefinitely, * or we just give them a false name. Since * dma_fence_ops.get_timeline_name is a debug feature, the occasional * lie seems justifiable. */ if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) return "signaled"; ctx = i915_request_gem_context(to_request(fence)); if (!ctx) return "[" DRIVER_NAME "]"; return ctx->name; } static bool i915_fence_signaled(struct dma_fence *fence) { return i915_request_completed(to_request(fence)); } static bool i915_fence_enable_signaling(struct dma_fence *fence) { return i915_request_enable_breadcrumb(to_request(fence)); } static signed long i915_fence_wait(struct dma_fence *fence, bool interruptible, signed long timeout) { return i915_request_wait(to_request(fence), interruptible | I915_WAIT_PRIORITY, timeout); } struct kmem_cache *i915_request_slab_cache(void) { return global.slab_requests; } static void i915_fence_release(struct dma_fence *fence) { struct i915_request *rq = to_request(fence); /* * The request is put onto a RCU freelist (i.e. the address * is immediately reused), mark the fences as being freed now. * Otherwise the debugobjects for the fences are only marked as * freed when the slab cache itself is freed, and so we would get * caught trying to reuse dead objects. */ i915_sw_fence_fini(&rq->submit); i915_sw_fence_fini(&rq->semaphore); /* Keep one request on each engine for reserved use under mempressure */ if (!cmpxchg(&rq->engine->request_pool, NULL, rq)) return; kmem_cache_free(global.slab_requests, rq); } const struct dma_fence_ops i915_fence_ops = { .get_driver_name = i915_fence_get_driver_name, .get_timeline_name = i915_fence_get_timeline_name, .enable_signaling = i915_fence_enable_signaling, .signaled = i915_fence_signaled, .wait = i915_fence_wait, .release = i915_fence_release, }; static void irq_execute_cb(struct irq_work *wrk) { struct execute_cb *cb = container_of(wrk, typeof(*cb), work); i915_sw_fence_complete(cb->fence); kmem_cache_free(global.slab_execute_cbs, cb); } static void irq_execute_cb_hook(struct irq_work *wrk) { struct execute_cb *cb = container_of(wrk, typeof(*cb), work); cb->hook(container_of(cb->fence, struct i915_request, submit), &cb->signal->fence); i915_request_put(cb->signal); irq_execute_cb(wrk); } static void __notify_execute_cb(struct i915_request *rq) { struct execute_cb *cb; lockdep_assert_held(&rq->lock); if (list_empty(&rq->execute_cb)) return; list_for_each_entry(cb, &rq->execute_cb, link) irq_work_queue(&cb->work); /* * XXX Rollback on __i915_request_unsubmit() * * In the future, perhaps when we have an active time-slicing scheduler, * it will be interesting to unsubmit parallel execution and remove * busywaits from the GPU until their master is restarted. This is * quite hairy, we have to carefully rollback the fence and do a * preempt-to-idle cycle on the target engine, all the while the * master execute_cb may refire. */ INIT_LIST_HEAD(&rq->execute_cb); } static inline void remove_from_client(struct i915_request *request) { struct drm_i915_file_private *file_priv; if (!READ_ONCE(request->file_priv)) return; rcu_read_lock(); file_priv = xchg(&request->file_priv, NULL); if (file_priv) { spin_lock(&file_priv->mm.lock); list_del(&request->client_link); spin_unlock(&file_priv->mm.lock); } rcu_read_unlock(); } static void free_capture_list(struct i915_request *request) { struct i915_capture_list *capture; capture = fetch_and_zero(&request->capture_list); while (capture) { struct i915_capture_list *next = capture->next; kfree(capture); capture = next; } } static void __i915_request_fill(struct i915_request *rq, u8 val) { void *vaddr = rq->ring->vaddr; u32 head; head = rq->infix; if (rq->postfix < head) { memset(vaddr + head, val, rq->ring->size - head); head = 0; } memset(vaddr + head, val, rq->postfix - head); } static void remove_from_engine(struct i915_request *rq) { struct intel_engine_cs *engine, *locked; /* * Virtual engines complicate acquiring the engine timeline lock, * as their rq->engine pointer is not stable until under that * engine lock. The simple ploy we use is to take the lock then * check that the rq still belongs to the newly locked engine. */ locked = READ_ONCE(rq->engine); spin_lock_irq(&locked->active.lock); while (unlikely(locked != (engine = READ_ONCE(rq->engine)))) { spin_unlock(&locked->active.lock); spin_lock(&engine->active.lock); locked = engine; } list_del_init(&rq->sched.link); clear_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags); clear_bit(I915_FENCE_FLAG_HOLD, &rq->fence.flags); spin_unlock_irq(&locked->active.lock); } bool i915_request_retire(struct i915_request *rq) { if (!i915_request_completed(rq)) return false; RQ_TRACE(rq, "\n"); GEM_BUG_ON(!i915_sw_fence_signaled(&rq->submit)); trace_i915_request_retire(rq); /* * We know the GPU must have read the request to have * sent us the seqno + interrupt, so use the position * of tail of the request to update the last known position * of the GPU head. * * Note this requires that we are always called in request * completion order. */ GEM_BUG_ON(!list_is_first(&rq->link, &i915_request_timeline(rq)->requests)); if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)) /* Poison before we release our space in the ring */ __i915_request_fill(rq, POISON_FREE); rq->ring->head = rq->postfix; /* * We only loosely track inflight requests across preemption, * and so we may find ourselves attempting to retire a _completed_ * request that we have removed from the HW and put back on a run * queue. */ remove_from_engine(rq); spin_lock_irq(&rq->lock); i915_request_mark_complete(rq); if (!i915_request_signaled(rq)) dma_fence_signal_locked(&rq->fence); if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &rq->fence.flags)) i915_request_cancel_breadcrumb(rq); if (i915_request_has_waitboost(rq)) { GEM_BUG_ON(!atomic_read(&rq->engine->gt->rps.num_waiters)); atomic_dec(&rq->engine->gt->rps.num_waiters); } if (!test_bit(I915_FENCE_FLAG_ACTIVE, &rq->fence.flags)) { set_bit(I915_FENCE_FLAG_ACTIVE, &rq->fence.flags); __notify_execute_cb(rq); } GEM_BUG_ON(!list_empty(&rq->execute_cb)); spin_unlock_irq(&rq->lock); remove_from_client(rq); __list_del_entry(&rq->link); /* poison neither prev/next (RCU walks) */ intel_context_exit(rq->context); intel_context_unpin(rq->context); free_capture_list(rq); i915_sched_node_fini(&rq->sched); i915_request_put(rq); return true; } void i915_request_retire_upto(struct i915_request *rq) { struct intel_timeline * const tl = i915_request_timeline(rq); struct i915_request *tmp; RQ_TRACE(rq, "\n"); GEM_BUG_ON(!i915_request_completed(rq)); do { tmp = list_first_entry(&tl->requests, typeof(*tmp), link); } while (i915_request_retire(tmp) && tmp != rq); } static int __await_execution(struct i915_request *rq, struct i915_request *signal, void (*hook)(struct i915_request *rq, struct dma_fence *signal), gfp_t gfp) { struct execute_cb *cb; if (i915_request_is_active(signal)) { if (hook) hook(rq, &signal->fence); return 0; } cb = kmem_cache_alloc(global.slab_execute_cbs, gfp); if (!cb) return -ENOMEM; cb->fence = &rq->submit; i915_sw_fence_await(cb->fence); init_irq_work(&cb->work, irq_execute_cb); if (hook) { cb->hook = hook; cb->signal = i915_request_get(signal); cb->work.func = irq_execute_cb_hook; } spin_lock_irq(&signal->lock); if (i915_request_is_active(signal)) { if (hook) { hook(rq, &signal->fence); i915_request_put(signal); } i915_sw_fence_complete(cb->fence); kmem_cache_free(global.slab_execute_cbs, cb); } else { list_add_tail(&cb->link, &signal->execute_cb); } spin_unlock_irq(&signal->lock); /* Copy across semaphore status as we need the same behaviour */ rq->sched.flags |= signal->sched.flags; return 0; } static bool fatal_error(int error) { switch (error) { case 0: /* not an error! */ case -EAGAIN: /* innocent victim of a GT reset (__i915_request_reset) */ case -ETIMEDOUT: /* waiting for Godot (timer_i915_sw_fence_wake) */ return false; default: return true; } } void __i915_request_skip(struct i915_request *rq) { GEM_BUG_ON(!fatal_error(rq->fence.error)); if (rq->infix == rq->postfix) return; /* * As this request likely depends on state from the lost * context, clear out all the user operations leaving the * breadcrumb at the end (so we get the fence notifications). */ __i915_request_fill(rq, 0); rq->infix = rq->postfix; } void i915_request_set_error_once(struct i915_request *rq, int error) { int old; GEM_BUG_ON(!IS_ERR_VALUE((long)error)); if (i915_request_signaled(rq)) return; old = READ_ONCE(rq->fence.error); do { if (fatal_error(old)) return; } while (!try_cmpxchg(&rq->fence.error, &old, error)); } bool __i915_request_submit(struct i915_request *request) { struct intel_engine_cs *engine = request->engine; bool result = false; RQ_TRACE(request, "\n"); GEM_BUG_ON(!irqs_disabled()); lockdep_assert_held(&engine->active.lock); /* * With the advent of preempt-to-busy, we frequently encounter * requests that we have unsubmitted from HW, but left running * until the next ack and so have completed in the meantime. On * resubmission of that completed request, we can skip * updating the payload, and execlists can even skip submitting * the request. * * We must remove the request from the caller's priority queue, * and the caller must only call us when the request is in their * priority queue, under the active.lock. This ensures that the * request has *not* yet been retired and we can safely move * the request into the engine->active.list where it will be * dropped upon retiring. (Otherwise if resubmit a *retired* * request, this would be a horrible use-after-free.) */ if (i915_request_completed(request)) goto xfer; if (unlikely(intel_context_is_banned(request->context))) i915_request_set_error_once(request, -EIO); if (unlikely(fatal_error(request->fence.error))) __i915_request_skip(request); /* * Are we using semaphores when the gpu is already saturated? * * Using semaphores incurs a cost in having the GPU poll a * memory location, busywaiting for it to change. The continual * memory reads can have a noticeable impact on the rest of the * system with the extra bus traffic, stalling the cpu as it too * tries to access memory across the bus (perf stat -e bus-cycles). * * If we installed a semaphore on this request and we only submit * the request after the signaler completed, that indicates the * system is overloaded and using semaphores at this time only * increases the amount of work we are doing. If so, we disable * further use of semaphores until we are idle again, whence we * optimistically try again. */ if (request->sched.semaphores && i915_sw_fence_signaled(&request->semaphore)) engine->saturated |= request->sched.semaphores; engine->emit_fini_breadcrumb(request, request->ring->vaddr + request->postfix); trace_i915_request_execute(request); engine->serial++; result = true; xfer: /* We may be recursing from the signal callback of another i915 fence */ spin_lock_nested(&request->lock, SINGLE_DEPTH_NESTING); if (!test_and_set_bit(I915_FENCE_FLAG_ACTIVE, &request->fence.flags)) { list_move_tail(&request->sched.link, &engine->active.requests); clear_bit(I915_FENCE_FLAG_PQUEUE, &request->fence.flags); } if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &request->fence.flags) && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &request->fence.flags) && !i915_request_enable_breadcrumb(request)) intel_engine_signal_breadcrumbs(engine); __notify_execute_cb(request); spin_unlock(&request->lock); return result; } void i915_request_submit(struct i915_request *request) { struct intel_engine_cs *engine = request->engine; unsigned long flags; /* Will be called from irq-context when using foreign fences. */ spin_lock_irqsave(&engine->active.lock, flags); __i915_request_submit(request); spin_unlock_irqrestore(&engine->active.lock, flags); } void __i915_request_unsubmit(struct i915_request *request) { struct intel_engine_cs *engine = request->engine; RQ_TRACE(request, "\n"); GEM_BUG_ON(!irqs_disabled()); lockdep_assert_held(&engine->active.lock); /* * Only unwind in reverse order, required so that the per-context list * is kept in seqno/ring order. */ /* We may be recursing from the signal callback of another i915 fence */ spin_lock_nested(&request->lock, SINGLE_DEPTH_NESTING); if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &request->fence.flags)) i915_request_cancel_breadcrumb(request); GEM_BUG_ON(!test_bit(I915_FENCE_FLAG_ACTIVE, &request->fence.flags)); clear_bit(I915_FENCE_FLAG_ACTIVE, &request->fence.flags); spin_unlock(&request->lock); /* We've already spun, don't charge on resubmitting. */ if (request->sched.semaphores && i915_request_started(request)) { request->sched.attr.priority |= I915_PRIORITY_NOSEMAPHORE; request->sched.semaphores = 0; } /* * We don't need to wake_up any waiters on request->execute, they * will get woken by any other event or us re-adding this request * to the engine timeline (__i915_request_submit()). The waiters * should be quite adapt at finding that the request now has a new * global_seqno to the one they went to sleep on. */ } void i915_request_unsubmit(struct i915_request *request) { struct intel_engine_cs *engine = request->engine; unsigned long flags; /* Will be called from irq-context when using foreign fences. */ spin_lock_irqsave(&engine->active.lock, flags); __i915_request_unsubmit(request); spin_unlock_irqrestore(&engine->active.lock, flags); } static int __i915_sw_fence_call submit_notify(struct i915_sw_fence *fence, enum i915_sw_fence_notify state) { struct i915_request *request = container_of(fence, typeof(*request), submit); switch (state) { case FENCE_COMPLETE: trace_i915_request_submit(request); if (unlikely(fence->error)) i915_request_set_error_once(request, fence->error); /* * We need to serialize use of the submit_request() callback * with its hotplugging performed during an emergency * i915_gem_set_wedged(). We use the RCU mechanism to mark the * critical section in order to force i915_gem_set_wedged() to * wait until the submit_request() is completed before * proceeding. */ rcu_read_lock(); request->engine->submit_request(request); rcu_read_unlock(); break; case FENCE_FREE: i915_request_put(request); break; } return NOTIFY_DONE; } static void irq_semaphore_cb(struct irq_work *wrk) { struct i915_request *rq = container_of(wrk, typeof(*rq), semaphore_work); i915_schedule_bump_priority(rq, I915_PRIORITY_NOSEMAPHORE); i915_request_put(rq); } static int __i915_sw_fence_call semaphore_notify(struct i915_sw_fence *fence, enum i915_sw_fence_notify state) { struct i915_request *rq = container_of(fence, typeof(*rq), semaphore); switch (state) { case FENCE_COMPLETE: if (!(READ_ONCE(rq->sched.attr.priority) & I915_PRIORITY_NOSEMAPHORE)) { i915_request_get(rq); init_irq_work(&rq->semaphore_work, irq_semaphore_cb); irq_work_queue(&rq->semaphore_work); } break; case FENCE_FREE: i915_request_put(rq); break; } return NOTIFY_DONE; } static void retire_requests(struct intel_timeline *tl) { struct i915_request *rq, *rn; list_for_each_entry_safe(rq, rn, &tl->requests, link) if (!i915_request_retire(rq)) break; } static noinline struct i915_request * request_alloc_slow(struct intel_timeline *tl, struct i915_request **rsvd, gfp_t gfp) { struct i915_request *rq; /* If we cannot wait, dip into our reserves */ if (!gfpflags_allow_blocking(gfp)) { rq = xchg(rsvd, NULL); if (!rq) /* Use the normal failure path for one final WARN */ goto out; return rq; } if (list_empty(&tl->requests)) goto out; /* Move our oldest request to the slab-cache (if not in use!) */ rq = list_first_entry(&tl->requests, typeof(*rq), link); i915_request_retire(rq); rq = kmem_cache_alloc(global.slab_requests, gfp | __GFP_RETRY_MAYFAIL | __GFP_NOWARN); if (rq) return rq; /* Ratelimit ourselves to prevent oom from malicious clients */ rq = list_last_entry(&tl->requests, typeof(*rq), link); cond_synchronize_rcu(rq->rcustate); /* Retire our old requests in the hope that we free some */ retire_requests(tl); out: return kmem_cache_alloc(global.slab_requests, gfp); } static void __i915_request_ctor(void *arg) { struct i915_request *rq = arg; spin_lock_init(&rq->lock); i915_sched_node_init(&rq->sched); i915_sw_fence_init(&rq->submit, submit_notify); i915_sw_fence_init(&rq->semaphore, semaphore_notify); dma_fence_init(&rq->fence, &i915_fence_ops, &rq->lock, 0, 0); rq->file_priv = NULL; rq->capture_list = NULL; INIT_LIST_HEAD(&rq->execute_cb); } struct i915_request * __i915_request_create(struct intel_context *ce, gfp_t gfp) { struct intel_timeline *tl = ce->timeline; struct i915_request *rq; u32 seqno; int ret; might_sleep_if(gfpflags_allow_blocking(gfp)); /* Check that the caller provided an already pinned context */ __intel_context_pin(ce); /* * Beware: Dragons be flying overhead. * * We use RCU to look up requests in flight. The lookups may * race with the request being allocated from the slab freelist. * That is the request we are writing to here, may be in the process * of being read by __i915_active_request_get_rcu(). As such, * we have to be very careful when overwriting the contents. During * the RCU lookup, we change chase the request->engine pointer, * read the request->global_seqno and increment the reference count. * * The reference count is incremented atomically. If it is zero, * the lookup knows the request is unallocated and complete. Otherwise, * it is either still in use, or has been reallocated and reset * with dma_fence_init(). This increment is safe for release as we * check that the request we have a reference to and matches the active * request. * * Before we increment the refcount, we chase the request->engine * pointer. We must not call kmem_cache_zalloc() or else we set * that pointer to NULL and cause a crash during the lookup. If * we see the request is completed (based on the value of the * old engine and seqno), the lookup is complete and reports NULL. * If we decide the request is not completed (new engine or seqno), * then we grab a reference and double check that it is still the * active request - which it won't be and restart the lookup. * * Do not use kmem_cache_zalloc() here! */ rq = kmem_cache_alloc(global.slab_requests, gfp | __GFP_RETRY_MAYFAIL | __GFP_NOWARN); if (unlikely(!rq)) { rq = request_alloc_slow(tl, &ce->engine->request_pool, gfp); if (!rq) { ret = -ENOMEM; goto err_unreserve; } } rq->i915 = ce->engine->i915; rq->context = ce; rq->engine = ce->engine; rq->ring = ce->ring; rq->execution_mask = ce->engine->mask; kref_init(&rq->fence.refcount); rq->fence.flags = 0; rq->fence.error = 0; INIT_LIST_HEAD(&rq->fence.cb_list); ret = intel_timeline_get_seqno(tl, rq, &seqno); if (ret) goto err_free; rq->fence.context = tl->fence_context; rq->fence.seqno = seqno; RCU_INIT_POINTER(rq->timeline, tl); RCU_INIT_POINTER(rq->hwsp_cacheline, tl->hwsp_cacheline); rq->hwsp_seqno = tl->hwsp_seqno; GEM_BUG_ON(i915_request_completed(rq)); rq->rcustate = get_state_synchronize_rcu(); /* acts as smp_mb() */ /* We bump the ref for the fence chain */ i915_sw_fence_reinit(&i915_request_get(rq)->submit); i915_sw_fence_reinit(&i915_request_get(rq)->semaphore); i915_sched_node_reinit(&rq->sched); /* No zalloc, everything must be cleared after use */ rq->batch = NULL; GEM_BUG_ON(rq->file_priv); GEM_BUG_ON(rq->capture_list); GEM_BUG_ON(!list_empty(&rq->execute_cb)); /* * Reserve space in the ring buffer for all the commands required to * eventually emit this request. This is to guarantee that the * i915_request_add() call can't fail. Note that the reserve may need * to be redone if the request is not actually submitted straight * away, e.g. because a GPU scheduler has deferred it. * * Note that due to how we add reserved_space to intel_ring_begin() * we need to double our request to ensure that if we need to wrap * around inside i915_request_add() there is sufficient space at * the beginning of the ring as well. */ rq->reserved_space = 2 * rq->engine->emit_fini_breadcrumb_dw * sizeof(u32); /* * Record the position of the start of the request so that * should we detect the updated seqno part-way through the * GPU processing the request, we never over-estimate the * position of the head. */ rq->head = rq->ring->emit; ret = rq->engine->request_alloc(rq); if (ret) goto err_unwind; rq->infix = rq->ring->emit; /* end of header; start of user payload */ intel_context_mark_active(ce); list_add_tail_rcu(&rq->link, &tl->requests); return rq; err_unwind: ce->ring->emit = rq->head; /* Make sure we didn't add ourselves to external state before freeing */ GEM_BUG_ON(!list_empty(&rq->sched.signalers_list)); GEM_BUG_ON(!list_empty(&rq->sched.waiters_list)); err_free: kmem_cache_free(global.slab_requests, rq); err_unreserve: intel_context_unpin(ce); return ERR_PTR(ret); } struct i915_request * i915_request_create(struct intel_context *ce) { struct i915_request *rq; struct intel_timeline *tl; tl = intel_context_timeline_lock(ce); if (IS_ERR(tl)) return ERR_CAST(tl); /* Move our oldest request to the slab-cache (if not in use!) */ rq = list_first_entry(&tl->requests, typeof(*rq), link); if (!list_is_last(&rq->link, &tl->requests)) i915_request_retire(rq); intel_context_enter(ce); rq = __i915_request_create(ce, GFP_KERNEL); intel_context_exit(ce); /* active reference transferred to request */ if (IS_ERR(rq)) goto err_unlock; /* Check that we do not interrupt ourselves with a new request */ rq->cookie = lockdep_pin_lock(&tl->mutex); return rq; err_unlock: intel_context_timeline_unlock(tl); return rq; } static int i915_request_await_start(struct i915_request *rq, struct i915_request *signal) { struct dma_fence *fence; int err; if (i915_request_timeline(rq) == rcu_access_pointer(signal->timeline)) return 0; if (i915_request_started(signal)) return 0; fence = NULL; rcu_read_lock(); spin_lock_irq(&signal->lock); do { struct list_head *pos = READ_ONCE(signal->link.prev); struct i915_request *prev; /* Confirm signal has not been retired, the link is valid */ if (unlikely(i915_request_started(signal))) break; /* Is signal the earliest request on its timeline? */ if (pos == &rcu_dereference(signal->timeline)->requests) break; /* * Peek at the request before us in the timeline. That * request will only be valid before it is retired, so * after acquiring a reference to it, confirm that it is * still part of the signaler's timeline. */ prev = list_entry(pos, typeof(*prev), link); if (!i915_request_get_rcu(prev)) break; /* After the strong barrier, confirm prev is still attached */ if (unlikely(READ_ONCE(prev->link.next) != &signal->link)) { i915_request_put(prev); break; } fence = &prev->fence; } while (0); spin_unlock_irq(&signal->lock); rcu_read_unlock(); if (!fence) return 0; err = 0; if (!intel_timeline_sync_is_later(i915_request_timeline(rq), fence)) err = i915_sw_fence_await_dma_fence(&rq->submit, fence, 0, I915_FENCE_GFP); dma_fence_put(fence); return err; } static intel_engine_mask_t already_busywaiting(struct i915_request *rq) { /* * Polling a semaphore causes bus traffic, delaying other users of * both the GPU and CPU. We want to limit the impact on others, * while taking advantage of early submission to reduce GPU * latency. Therefore we restrict ourselves to not using more * than one semaphore from each source, and not using a semaphore * if we have detected the engine is saturated (i.e. would not be * submitted early and cause bus traffic reading an already passed * semaphore). * * See the are-we-too-late? check in __i915_request_submit(). */ return rq->sched.semaphores | READ_ONCE(rq->engine->saturated); } static int __emit_semaphore_wait(struct i915_request *to, struct i915_request *from, u32 seqno) { const int has_token = INTEL_GEN(to->i915) >= 12; u32 hwsp_offset; int len, err; u32 *cs; GEM_BUG_ON(INTEL_GEN(to->i915) < 8); /* We need to pin the signaler's HWSP until we are finished reading. */ err = intel_timeline_read_hwsp(from, to, &hwsp_offset); if (err) return err; len = 4; if (has_token) len += 2; cs = intel_ring_begin(to, len); if (IS_ERR(cs)) return PTR_ERR(cs); /* * Using greater-than-or-equal here means we have to worry * about seqno wraparound. To side step that issue, we swap * the timeline HWSP upon wrapping, so that everyone listening * for the old (pre-wrap) values do not see the much smaller * (post-wrap) values than they were expecting (and so wait * forever). */ *cs++ = (MI_SEMAPHORE_WAIT | MI_SEMAPHORE_GLOBAL_GTT | MI_SEMAPHORE_POLL | MI_SEMAPHORE_SAD_GTE_SDD) + has_token; *cs++ = seqno; *cs++ = hwsp_offset; *cs++ = 0; if (has_token) { *cs++ = 0; *cs++ = MI_NOOP; } intel_ring_advance(to, cs); return 0; } static int emit_semaphore_wait(struct i915_request *to, struct i915_request *from, gfp_t gfp) { const intel_engine_mask_t mask = READ_ONCE(from->engine)->mask; if (!intel_context_use_semaphores(to->context)) goto await_fence; if (!rcu_access_pointer(from->hwsp_cacheline)) goto await_fence; /* Just emit the first semaphore we see as request space is limited. */ if (already_busywaiting(to) & mask) goto await_fence; if (i915_request_await_start(to, from) < 0) goto await_fence; /* Only submit our spinner after the signaler is running! */ if (__await_execution(to, from, NULL, gfp)) goto await_fence; if (__emit_semaphore_wait(to, from, from->fence.seqno)) goto await_fence; to->sched.semaphores |= mask; to->sched.flags |= I915_SCHED_HAS_SEMAPHORE_CHAIN; return 0; await_fence: return i915_sw_fence_await_dma_fence(&to->submit, &from->fence, 0, I915_FENCE_GFP); } static int i915_request_await_request(struct i915_request *to, struct i915_request *from) { int ret; GEM_BUG_ON(to == from); GEM_BUG_ON(to->timeline == from->timeline); if (i915_request_completed(from)) { i915_sw_fence_set_error_once(&to->submit, from->fence.error); return 0; } if (to->engine->schedule) { ret = i915_sched_node_add_dependency(&to->sched, &from->sched); if (ret < 0) return ret; } if (to->engine == from->engine) ret = i915_sw_fence_await_sw_fence_gfp(&to->submit, &from->submit, I915_FENCE_GFP); else ret = emit_semaphore_wait(to, from, I915_FENCE_GFP); if (ret < 0) return ret; if (to->sched.flags & I915_SCHED_HAS_SEMAPHORE_CHAIN) { ret = i915_sw_fence_await_dma_fence(&to->semaphore, &from->fence, 0, I915_FENCE_GFP); if (ret < 0) return ret; } return 0; } int i915_request_await_dma_fence(struct i915_request *rq, struct dma_fence *fence) { struct dma_fence **child = &fence; unsigned int nchild = 1; int ret; /* * Note that if the fence-array was created in signal-on-any mode, * we should *not* decompose it into its individual fences. However, * we don't currently store which mode the fence-array is operating * in. Fortunately, the only user of signal-on-any is private to * amdgpu and we should not see any incoming fence-array from * sync-file being in signal-on-any mode. */ if (dma_fence_is_array(fence)) { struct dma_fence_array *array = to_dma_fence_array(fence); child = array->fences; nchild = array->num_fences; GEM_BUG_ON(!nchild); } do { fence = *child++; if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) { i915_sw_fence_set_error_once(&rq->submit, fence->error); continue; } /* * Requests on the same timeline are explicitly ordered, along * with their dependencies, by i915_request_add() which ensures * that requests are submitted in-order through each ring. */ if (fence->context == rq->fence.context) continue; /* Squash repeated waits to the same timelines */ if (fence->context && intel_timeline_sync_is_later(i915_request_timeline(rq), fence)) continue; if (dma_fence_is_i915(fence)) ret = i915_request_await_request(rq, to_request(fence)); else ret = i915_sw_fence_await_dma_fence(&rq->submit, fence, fence->context ? I915_FENCE_TIMEOUT : 0, I915_FENCE_GFP); if (ret < 0) return ret; /* Record the latest fence used against each timeline */ if (fence->context) intel_timeline_sync_set(i915_request_timeline(rq), fence); } while (--nchild); return 0; } static bool intel_timeline_sync_has_start(struct intel_timeline *tl, struct dma_fence *fence) { return __intel_timeline_sync_is_later(tl, fence->context, fence->seqno - 1); } static int intel_timeline_sync_set_start(struct intel_timeline *tl, const struct dma_fence *fence) { return __intel_timeline_sync_set(tl, fence->context, fence->seqno - 1); } static int __i915_request_await_execution(struct i915_request *to, struct i915_request *from, void (*hook)(struct i915_request *rq, struct dma_fence *signal)) { int err; GEM_BUG_ON(intel_context_is_barrier(from->context)); /* Submit both requests at the same time */ err = __await_execution(to, from, hook, I915_FENCE_GFP); if (err) return err; /* Squash repeated depenendices to the same timelines */ if (intel_timeline_sync_has_start(i915_request_timeline(to), &from->fence)) return 0; /* * Wait until the start of this request. * * The execution cb fires when we submit the request to HW. But in * many cases this may be long before the request itself is ready to * run (consider that we submit 2 requests for the same context, where * the request of interest is behind an indefinite spinner). So we hook * up to both to reduce our queues and keep the execution lag minimised * in the worst case, though we hope that the await_start is elided. */ err = i915_request_await_start(to, from); if (err < 0) return err; /* * Ensure both start together [after all semaphores in signal] * * Now that we are queued to the HW at roughly the same time (thanks * to the execute cb) and are ready to run at roughly the same time * (thanks to the await start), our signaler may still be indefinitely * delayed by waiting on a semaphore from a remote engine. If our * signaler depends on a semaphore, so indirectly do we, and we do not * want to start our payload until our signaler also starts theirs. * So we wait. * * However, there is also a second condition for which we need to wait * for the precise start of the signaler. Consider that the signaler * was submitted in a chain of requests following another context * (with just an ordinary intra-engine fence dependency between the * two). In this case the signaler is queued to HW, but not for * immediate execution, and so we must wait until it reaches the * active slot. */ if (intel_engine_has_semaphores(to->engine)) { err = __emit_semaphore_wait(to, from, from->fence.seqno - 1); if (err < 0) return err; } /* Couple the dependency tree for PI on this exposed to->fence */ if (to->engine->schedule) { err = i915_sched_node_add_dependency(&to->sched, &from->sched); if (err < 0) return err; } return intel_timeline_sync_set_start(i915_request_timeline(to), &from->fence); } int i915_request_await_execution(struct i915_request *rq, struct dma_fence *fence, void (*hook)(struct i915_request *rq, struct dma_fence *signal)) { struct dma_fence **child = &fence; unsigned int nchild = 1; int ret; if (dma_fence_is_array(fence)) { struct dma_fence_array *array = to_dma_fence_array(fence); /* XXX Error for signal-on-any fence arrays */ child = array->fences; nchild = array->num_fences; GEM_BUG_ON(!nchild); } do { fence = *child++; if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) { i915_sw_fence_set_error_once(&rq->submit, fence->error); continue; } /* * We don't squash repeated fence dependencies here as we * want to run our callback in all cases. */ if (dma_fence_is_i915(fence)) ret = __i915_request_await_execution(rq, to_request(fence), hook); else ret = i915_sw_fence_await_dma_fence(&rq->submit, fence, I915_FENCE_TIMEOUT, GFP_KERNEL); if (ret < 0) return ret; } while (--nchild); return 0; } /** * i915_request_await_object - set this request to (async) wait upon a bo * @to: request we are wishing to use * @obj: object which may be in use on another ring. * @write: whether the wait is on behalf of a writer * * This code is meant to abstract object synchronization with the GPU. * Conceptually we serialise writes between engines inside the GPU. * We only allow one engine to write into a buffer at any time, but * multiple readers. To ensure each has a coherent view of memory, we must: * * - If there is an outstanding write request to the object, the new * request must wait for it to complete (either CPU or in hw, requests * on the same ring will be naturally ordered). * * - If we are a write request (pending_write_domain is set), the new * request must wait for outstanding read requests to complete. * * Returns 0 if successful, else propagates up the lower layer error. */ int i915_request_await_object(struct i915_request *to, struct drm_i915_gem_object *obj, bool write) { struct dma_fence *excl; int ret = 0; if (write) { struct dma_fence **shared; unsigned int count, i; ret = dma_resv_get_fences_rcu(obj->base.resv, &excl, &count, &shared); if (ret) return ret; for (i = 0; i < count; i++) { ret = i915_request_await_dma_fence(to, shared[i]); if (ret) break; dma_fence_put(shared[i]); } for (; i < count; i++) dma_fence_put(shared[i]); kfree(shared); } else { excl = dma_resv_get_excl_rcu(obj->base.resv); } if (excl) { if (ret == 0) ret = i915_request_await_dma_fence(to, excl); dma_fence_put(excl); } return ret; } static struct i915_request * __i915_request_add_to_timeline(struct i915_request *rq) { struct intel_timeline *timeline = i915_request_timeline(rq); struct i915_request *prev; /* * Dependency tracking and request ordering along the timeline * is special cased so that we can eliminate redundant ordering * operations while building the request (we know that the timeline * itself is ordered, and here we guarantee it). * * As we know we will need to emit tracking along the timeline, * we embed the hooks into our request struct -- at the cost of * having to have specialised no-allocation interfaces (which will * be beneficial elsewhere). * * A second benefit to open-coding i915_request_await_request is * that we can apply a slight variant of the rules specialised * for timelines that jump between engines (such as virtual engines). * If we consider the case of virtual engine, we must emit a dma-fence * to prevent scheduling of the second request until the first is * complete (to maximise our greedy late load balancing) and this * precludes optimising to use semaphores serialisation of a single * timeline across engines. */ prev = to_request(__i915_active_fence_set(&timeline->last_request, &rq->fence)); if (prev && !i915_request_completed(prev)) { /* * The requests are supposed to be kept in order. However, * we need to be wary in case the timeline->last_request * is used as a barrier for external modification to this * context. */ GEM_BUG_ON(prev->context == rq->context && i915_seqno_passed(prev->fence.seqno, rq->fence.seqno)); if (is_power_of_2(READ_ONCE(prev->engine)->mask | rq->engine->mask)) i915_sw_fence_await_sw_fence(&rq->submit, &prev->submit, &rq->submitq); else __i915_sw_fence_await_dma_fence(&rq->submit, &prev->fence, &rq->dmaq); if (rq->engine->schedule) __i915_sched_node_add_dependency(&rq->sched, &prev->sched, &rq->dep, 0); } /* * Make sure that no request gazumped us - if it was allocated after * our i915_request_alloc() and called __i915_request_add() before * us, the timeline will hold its seqno which is later than ours. */ GEM_BUG_ON(timeline->seqno != rq->fence.seqno); return prev; } /* * NB: This function is not allowed to fail. Doing so would mean the the * request is not being tracked for completion but the work itself is * going to happen on the hardware. This would be a Bad Thing(tm). */ struct i915_request *__i915_request_commit(struct i915_request *rq) { struct intel_engine_cs *engine = rq->engine; struct intel_ring *ring = rq->ring; u32 *cs; RQ_TRACE(rq, "\n"); /* * To ensure that this call will not fail, space for its emissions * should already have been reserved in the ring buffer. Let the ring * know that it is time to use that space up. */ GEM_BUG_ON(rq->reserved_space > ring->space); rq->reserved_space = 0; rq->emitted_jiffies = jiffies; /* * Record the position of the start of the breadcrumb so that * should we detect the updated seqno part-way through the * GPU processing the request, we never over-estimate the * position of the ring's HEAD. */ cs = intel_ring_begin(rq, engine->emit_fini_breadcrumb_dw); GEM_BUG_ON(IS_ERR(cs)); rq->postfix = intel_ring_offset(rq, cs); return __i915_request_add_to_timeline(rq); } void __i915_request_queue(struct i915_request *rq, const struct i915_sched_attr *attr) { /* * Let the backend know a new request has arrived that may need * to adjust the existing execution schedule due to a high priority * request - i.e. we may want to preempt the current request in order * to run a high priority dependency chain *before* we can execute this * request. * * This is called before the request is ready to run so that we can * decide whether to preempt the entire chain so that it is ready to * run at the earliest possible convenience. */ if (attr && rq->engine->schedule) rq->engine->schedule(rq, attr); i915_sw_fence_commit(&rq->semaphore); i915_sw_fence_commit(&rq->submit); } void i915_request_add(struct i915_request *rq) { struct intel_timeline * const tl = i915_request_timeline(rq); struct i915_sched_attr attr = {}; struct i915_gem_context *ctx; lockdep_assert_held(&tl->mutex); lockdep_unpin_lock(&tl->mutex, rq->cookie); trace_i915_request_add(rq); __i915_request_commit(rq); /* XXX placeholder for selftests */ rcu_read_lock(); ctx = rcu_dereference(rq->context->gem_context); if (ctx) attr = ctx->sched; rcu_read_unlock(); if (!(rq->sched.flags & I915_SCHED_HAS_SEMAPHORE_CHAIN)) attr.priority |= I915_PRIORITY_NOSEMAPHORE; if (list_empty(&rq->sched.signalers_list)) attr.priority |= I915_PRIORITY_WAIT; __i915_request_queue(rq, &attr); mutex_unlock(&tl->mutex); } static unsigned long local_clock_ns(unsigned int *cpu) { unsigned long t; /* * Cheaply and approximately convert from nanoseconds to microseconds. * The result and subsequent calculations are also defined in the same * approximate microseconds units. The principal source of timing * error here is from the simple truncation. * * Note that local_clock() is only defined wrt to the current CPU; * the comparisons are no longer valid if we switch CPUs. Instead of * blocking preemption for the entire busywait, we can detect the CPU * switch and use that as indicator of system load and a reason to * stop busywaiting, see busywait_stop(). */ *cpu = get_cpu(); t = local_clock(); put_cpu(); return t; } static bool busywait_stop(unsigned long timeout, unsigned int cpu) { unsigned int this_cpu; if (time_after(local_clock_ns(&this_cpu), timeout)) return true; return this_cpu != cpu; } static bool __i915_spin_request(const struct i915_request * const rq, int state) { unsigned long timeout_ns; unsigned int cpu; /* * Only wait for the request if we know it is likely to complete. * * We don't track the timestamps around requests, nor the average * request length, so we do not have a good indicator that this * request will complete within the timeout. What we do know is the * order in which requests are executed by the context and so we can * tell if the request has been started. If the request is not even * running yet, it is a fair assumption that it will not complete * within our relatively short timeout. */ if (!i915_request_is_running(rq)) return false; /* * When waiting for high frequency requests, e.g. during synchronous * rendering split between the CPU and GPU, the finite amount of time * required to set up the irq and wait upon it limits the response * rate. By busywaiting on the request completion for a short while we * can service the high frequency waits as quick as possible. However, * if it is a slow request, we want to sleep as quickly as possible. * The tradeoff between waiting and sleeping is roughly the time it * takes to sleep on a request, on the order of a microsecond. */ timeout_ns = READ_ONCE(rq->engine->props.max_busywait_duration_ns); timeout_ns += local_clock_ns(&cpu); do { if (i915_request_completed(rq)) return true; if (signal_pending_state(state, current)) break; if (busywait_stop(timeout_ns, cpu)) break; cpu_relax(); } while (!need_resched()); return false; } struct request_wait { struct dma_fence_cb cb; struct task_struct *tsk; }; static void request_wait_wake(struct dma_fence *fence, struct dma_fence_cb *cb) { struct request_wait *wait = container_of(cb, typeof(*wait), cb); wake_up_process(wait->tsk); } /** * i915_request_wait - wait until execution of request has finished * @rq: the request to wait upon * @flags: how to wait * @timeout: how long to wait in jiffies * * i915_request_wait() waits for the request to be completed, for a * maximum of @timeout jiffies (with MAX_SCHEDULE_TIMEOUT implying an * unbounded wait). * * Returns the remaining time (in jiffies) if the request completed, which may * be zero or -ETIME if the request is unfinished after the timeout expires. * May return -EINTR is called with I915_WAIT_INTERRUPTIBLE and a signal is * pending before the request completes. */ long i915_request_wait(struct i915_request *rq, unsigned int flags, long timeout) { const int state = flags & I915_WAIT_INTERRUPTIBLE ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE; struct request_wait wait; might_sleep(); GEM_BUG_ON(timeout < 0); if (dma_fence_is_signaled(&rq->fence)) return timeout; if (!timeout) return -ETIME; trace_i915_request_wait_begin(rq, flags); /* * We must never wait on the GPU while holding a lock as we * may need to perform a GPU reset. So while we don't need to * serialise wait/reset with an explicit lock, we do want * lockdep to detect potential dependency cycles. */ mutex_acquire(&rq->engine->gt->reset.mutex.dep_map, 0, 0, _THIS_IP_); /* * Optimistic spin before touching IRQs. * * We may use a rather large value here to offset the penalty of * switching away from the active task. Frequently, the client will * wait upon an old swapbuffer to throttle itself to remain within a * frame of the gpu. If the client is running in lockstep with the gpu, * then it should not be waiting long at all, and a sleep now will incur * extra scheduler latency in producing the next frame. To try to * avoid adding the cost of enabling/disabling the interrupt to the * short wait, we first spin to see if the request would have completed * in the time taken to setup the interrupt. * * We need upto 5us to enable the irq, and upto 20us to hide the * scheduler latency of a context switch, ignoring the secondary * impacts from a context switch such as cache eviction. * * The scheme used for low-latency IO is called "hybrid interrupt * polling". The suggestion there is to sleep until just before you * expect to be woken by the device interrupt and then poll for its * completion. That requires having a good predictor for the request * duration, which we currently lack. */ if (IS_ACTIVE(CONFIG_DRM_I915_MAX_REQUEST_BUSYWAIT) && __i915_spin_request(rq, state)) { dma_fence_signal(&rq->fence); goto out; } /* * This client is about to stall waiting for the GPU. In many cases * this is undesirable and limits the throughput of the system, as * many clients cannot continue processing user input/output whilst * blocked. RPS autotuning may take tens of milliseconds to respond * to the GPU load and thus incurs additional latency for the client. * We can circumvent that by promoting the GPU frequency to maximum * before we sleep. This makes the GPU throttle up much more quickly * (good for benchmarks and user experience, e.g. window animations), * but at a cost of spending more power processing the workload * (bad for battery). */ if (flags & I915_WAIT_PRIORITY) { if (!i915_request_started(rq) && INTEL_GEN(rq->i915) >= 6) intel_rps_boost(rq); i915_schedule_bump_priority(rq, I915_PRIORITY_WAIT); } wait.tsk = current; if (dma_fence_add_callback(&rq->fence, &wait.cb, request_wait_wake)) goto out; for (;;) { set_current_state(state); if (i915_request_completed(rq)) { dma_fence_signal(&rq->fence); break; } intel_engine_flush_submission(rq->engine); if (signal_pending_state(state, current)) { timeout = -ERESTARTSYS; break; } if (!timeout) { timeout = -ETIME; break; } timeout = io_schedule_timeout(timeout); } __set_current_state(TASK_RUNNING); dma_fence_remove_callback(&rq->fence, &wait.cb); out: mutex_release(&rq->engine->gt->reset.mutex.dep_map, _THIS_IP_); trace_i915_request_wait_end(rq); return timeout; } #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST) #include "selftests/mock_request.c" #include "selftests/i915_request.c" #endif static void i915_global_request_shrink(void) { kmem_cache_shrink(global.slab_execute_cbs); kmem_cache_shrink(global.slab_requests); } static void i915_global_request_exit(void) { kmem_cache_destroy(global.slab_execute_cbs); kmem_cache_destroy(global.slab_requests); } static struct i915_global_request global = { { .shrink = i915_global_request_shrink, .exit = i915_global_request_exit, } }; int __init i915_global_request_init(void) { global.slab_requests = kmem_cache_create("i915_request", sizeof(struct i915_request), __alignof__(struct i915_request), SLAB_HWCACHE_ALIGN | SLAB_RECLAIM_ACCOUNT | SLAB_TYPESAFE_BY_RCU, __i915_request_ctor); if (!global.slab_requests) return -ENOMEM; global.slab_execute_cbs = KMEM_CACHE(execute_cb, SLAB_HWCACHE_ALIGN | SLAB_RECLAIM_ACCOUNT | SLAB_TYPESAFE_BY_RCU); if (!global.slab_execute_cbs) goto err_requests; i915_global_register(&global.base); return 0; err_requests: kmem_cache_destroy(global.slab_requests); return -ENOMEM; }