139 lines
3.6 KiB
C
139 lines
3.6 KiB
C
/*
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* SPDX-License-Identifier: MIT
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*
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* Copyright © 2014-2016 Intel Corporation
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*/
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#include "gt/intel_engine.h"
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#include "i915_gem_ioctls.h"
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#include "i915_gem_object.h"
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static __always_inline u32 __busy_read_flag(u16 id)
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{
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if (id == (u16)I915_ENGINE_CLASS_INVALID)
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return 0xffff0000u;
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GEM_BUG_ON(id >= 16);
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return 0x10000u << id;
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}
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static __always_inline u32 __busy_write_id(u16 id)
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{
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/*
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* The uABI guarantees an active writer is also amongst the read
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* engines. This would be true if we accessed the activity tracking
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* under the lock, but as we perform the lookup of the object and
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* its activity locklessly we can not guarantee that the last_write
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* being active implies that we have set the same engine flag from
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* last_read - hence we always set both read and write busy for
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* last_write.
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*/
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if (id == (u16)I915_ENGINE_CLASS_INVALID)
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return 0xffffffffu;
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return (id + 1) | __busy_read_flag(id);
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}
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static __always_inline unsigned int
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__busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u16 id))
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{
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const struct i915_request *rq;
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/*
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* We have to check the current hw status of the fence as the uABI
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* guarantees forward progress. We could rely on the idle worker
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* to eventually flush us, but to minimise latency just ask the
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* hardware.
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*
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* Note we only report on the status of native fences.
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*/
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if (!dma_fence_is_i915(fence))
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return 0;
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/* opencode to_request() in order to avoid const warnings */
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rq = container_of(fence, const struct i915_request, fence);
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if (i915_request_completed(rq))
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return 0;
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/* Beware type-expansion follies! */
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BUILD_BUG_ON(!typecheck(u16, rq->engine->uabi_class));
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return flag(rq->engine->uabi_class);
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}
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static __always_inline unsigned int
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busy_check_reader(const struct dma_fence *fence)
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{
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return __busy_set_if_active(fence, __busy_read_flag);
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}
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static __always_inline unsigned int
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busy_check_writer(const struct dma_fence *fence)
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{
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if (!fence)
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return 0;
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return __busy_set_if_active(fence, __busy_write_id);
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}
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int
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i915_gem_busy_ioctl(struct drm_device *dev, void *data,
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struct drm_file *file)
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{
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struct drm_i915_gem_busy *args = data;
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struct drm_i915_gem_object *obj;
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struct dma_resv_list *list;
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unsigned int seq;
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int err;
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err = -ENOENT;
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rcu_read_lock();
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obj = i915_gem_object_lookup_rcu(file, args->handle);
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if (!obj)
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goto out;
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/*
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* A discrepancy here is that we do not report the status of
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* non-i915 fences, i.e. even though we may report the object as idle,
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* a call to set-domain may still stall waiting for foreign rendering.
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* This also means that wait-ioctl may report an object as busy,
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* where busy-ioctl considers it idle.
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*
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* We trade the ability to warn of foreign fences to report on which
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* i915 engines are active for the object.
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*
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* Alternatively, we can trade that extra information on read/write
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* activity with
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* args->busy =
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* !dma_resv_test_signaled(obj->resv, true);
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* to report the overall busyness. This is what the wait-ioctl does.
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*
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*/
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retry:
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seq = raw_read_seqcount(&obj->base.resv->seq);
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/* Translate the exclusive fence to the READ *and* WRITE engine */
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args->busy = busy_check_writer(dma_resv_excl_fence(obj->base.resv));
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/* Translate shared fences to READ set of engines */
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list = dma_resv_shared_list(obj->base.resv);
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if (list) {
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unsigned int shared_count = list->shared_count, i;
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for (i = 0; i < shared_count; ++i) {
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struct dma_fence *fence =
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rcu_dereference(list->shared[i]);
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args->busy |= busy_check_reader(fence);
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}
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}
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if (args->busy && read_seqcount_retry(&obj->base.resv->seq, seq))
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goto retry;
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err = 0;
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out:
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rcu_read_unlock();
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return err;
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}
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