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1/*
2 * Copyright © 2008-2018 Intel Corporation
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
21 * IN THE SOFTWARE.
22 *
23 */
24
25#ifndef I915_REQUEST_H
26#define I915_REQUEST_H
27
28#include <linux/dma-fence.h>
29#include <linux/lockdep.h>
30
31#include "gt/intel_context_types.h"
32#include "gt/intel_engine_types.h"
33
34#include "i915_gem.h"
35#include "i915_scheduler.h"
36#include "i915_selftest.h"
37#include "i915_sw_fence.h"
38
39#include <uapi/drm/i915_drm.h>
40
41struct drm_file;
42struct drm_i915_gem_object;
43struct i915_request;
44struct intel_timeline;
45struct intel_timeline_cacheline;
46
47struct i915_capture_list {
48 struct i915_capture_list *next;
49 struct i915_vma *vma;
50};
51
52enum {
53 /*
54 * I915_FENCE_FLAG_ACTIVE - this request is currently submitted to HW.
55 *
56 * Set by __i915_request_submit() on handing over to HW, and cleared
57 * by __i915_request_unsubmit() if we preempt this request.
58 *
59 * Finally cleared for consistency on retiring the request, when
60 * we know the HW is no longer running this request.
61 *
62 * See i915_request_is_active()
63 */
64 I915_FENCE_FLAG_ACTIVE = DMA_FENCE_FLAG_USER_BITS,
65
66 /*
67 * I915_FENCE_FLAG_SIGNAL - this request is currently on signal_list
68 *
69 * Internal bookkeeping used by the breadcrumb code to track when
70 * a request is on the various signal_list.
71 */
72 I915_FENCE_FLAG_SIGNAL,
73};
74
75/**
76 * Request queue structure.
77 *
78 * The request queue allows us to note sequence numbers that have been emitted
79 * and may be associated with active buffers to be retired.
80 *
81 * By keeping this list, we can avoid having to do questionable sequence
82 * number comparisons on buffer last_read|write_seqno. It also allows an
83 * emission time to be associated with the request for tracking how far ahead
84 * of the GPU the submission is.
85 *
86 * When modifying this structure be very aware that we perform a lockless
87 * RCU lookup of it that may race against reallocation of the struct
88 * from the slab freelist. We intentionally do not zero the structure on
89 * allocation so that the lookup can use the dangling pointers (and is
90 * cogniscent that those pointers may be wrong). Instead, everything that
91 * needs to be initialised must be done so explicitly.
92 *
93 * The requests are reference counted.
94 */
95struct i915_request {
96 struct dma_fence fence;
97 spinlock_t lock;
98
99 /** On Which ring this request was generated */
100 struct drm_i915_private *i915;
101
102 /**
103 * Context and ring buffer related to this request
104 * Contexts are refcounted, so when this request is associated with a
105 * context, we must increment the context's refcount, to guarantee that
106 * it persists while any request is linked to it. Requests themselves
107 * are also refcounted, so the request will only be freed when the last
108 * reference to it is dismissed, and the code in
109 * i915_request_free() will then decrement the refcount on the
110 * context.
111 */
112 struct i915_gem_context *gem_context;
113 struct intel_engine_cs *engine;
114 struct intel_context *hw_context;
115 struct intel_ring *ring;
116 struct intel_timeline *timeline;
117 struct list_head signal_link;
118
119 /*
120 * The rcu epoch of when this request was allocated. Used to judiciously
121 * apply backpressure on future allocations to ensure that under
122 * mempressure there is sufficient RCU ticks for us to reclaim our
123 * RCU protected slabs.
124 */
125 unsigned long rcustate;
126
127 /*
128 * We pin the timeline->mutex while constructing the request to
129 * ensure that no caller accidentally drops it during construction.
130 * The timeline->mutex must be held to ensure that only this caller
131 * can use the ring and manipulate the associated timeline during
132 * construction.
133 */
134 struct pin_cookie cookie;
135
136 /*
137 * Fences for the various phases in the request's lifetime.
138 *
139 * The submit fence is used to await upon all of the request's
140 * dependencies. When it is signaled, the request is ready to run.
141 * It is used by the driver to then queue the request for execution.
142 */
143 struct i915_sw_fence submit;
144 union {
145 wait_queue_entry_t submitq;
146 struct i915_sw_dma_fence_cb dmaq;
147 };
148 struct list_head execute_cb;
149 struct i915_sw_fence semaphore;
150
151 /*
152 * A list of everyone we wait upon, and everyone who waits upon us.
153 * Even though we will not be submitted to the hardware before the
154 * submit fence is signaled (it waits for all external events as well
155 * as our own requests), the scheduler still needs to know the
156 * dependency tree for the lifetime of the request (from execbuf
157 * to retirement), i.e. bidirectional dependency information for the
158 * request not tied to individual fences.
159 */
160 struct i915_sched_node sched;
161 struct i915_dependency dep;
162 intel_engine_mask_t execution_mask;
163
164 /*
165 * A convenience pointer to the current breadcrumb value stored in
166 * the HW status page (or our timeline's local equivalent). The full
167 * path would be rq->hw_context->ring->timeline->hwsp_seqno.
168 */
169 const u32 *hwsp_seqno;
170
171 /*
172 * If we need to access the timeline's seqno for this request in
173 * another request, we need to keep a read reference to this associated
174 * cacheline, so that we do not free and recycle it before the foreign
175 * observers have completed. Hence, we keep a pointer to the cacheline
176 * inside the timeline's HWSP vma, but it is only valid while this
177 * request has not completed and guarded by the timeline mutex.
178 */
179 struct intel_timeline_cacheline *hwsp_cacheline;
180
181 /** Position in the ring of the start of the request */
182 u32 head;
183
184 /** Position in the ring of the start of the user packets */
185 u32 infix;
186
187 /**
188 * Position in the ring of the start of the postfix.
189 * This is required to calculate the maximum available ring space
190 * without overwriting the postfix.
191 */
192 u32 postfix;
193
194 /** Position in the ring of the end of the whole request */
195 u32 tail;
196
197 /** Position in the ring of the end of any workarounds after the tail */
198 u32 wa_tail;
199
200 /** Preallocate space in the ring for the emitting the request */
201 u32 reserved_space;
202
203 /** Batch buffer related to this request if any (used for
204 * error state dump only).
205 */
206 struct i915_vma *batch;
207 /**
208 * Additional buffers requested by userspace to be captured upon
209 * a GPU hang. The vma/obj on this list are protected by their
210 * active reference - all objects on this list must also be
211 * on the active_list (of their final request).
212 */
213 struct i915_capture_list *capture_list;
214 struct list_head active_list;
215
216 /** Time at which this request was emitted, in jiffies. */
217 unsigned long emitted_jiffies;
218
219 unsigned long flags;
220#define I915_REQUEST_WAITBOOST BIT(0)
221#define I915_REQUEST_NOPREEMPT BIT(1)
222
223 /** timeline->request entry for this request */
224 struct list_head link;
225
226 struct drm_i915_file_private *file_priv;
227 /** file_priv list entry for this request */
228 struct list_head client_link;
229
230 I915_SELFTEST_DECLARE(struct {
231 struct list_head link;
232 unsigned long delay;
233 } mock;)
234};
235
236#define I915_FENCE_GFP (GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN)
237
238extern const struct dma_fence_ops i915_fence_ops;
239
240static inline bool dma_fence_is_i915(const struct dma_fence *fence)
241{
242 return fence->ops == &i915_fence_ops;
243}
244
245struct i915_request * __must_check
246__i915_request_create(struct intel_context *ce, gfp_t gfp);
247struct i915_request * __must_check
248i915_request_create(struct intel_context *ce);
249
250struct i915_request *__i915_request_commit(struct i915_request *request);
251void __i915_request_queue(struct i915_request *rq,
252 const struct i915_sched_attr *attr);
253
254void i915_request_retire_upto(struct i915_request *rq);
255
256static inline struct i915_request *
257to_request(struct dma_fence *fence)
258{
259 /* We assume that NULL fence/request are interoperable */
260 BUILD_BUG_ON(offsetof(struct i915_request, fence) != 0);
261 GEM_BUG_ON(fence && !dma_fence_is_i915(fence));
262 return container_of(fence, struct i915_request, fence);
263}
264
265static inline struct i915_request *
266i915_request_get(struct i915_request *rq)
267{
268 return to_request(dma_fence_get(&rq->fence));
269}
270
271static inline struct i915_request *
272i915_request_get_rcu(struct i915_request *rq)
273{
274 return to_request(dma_fence_get_rcu(&rq->fence));
275}
276
277static inline void
278i915_request_put(struct i915_request *rq)
279{
280 dma_fence_put(&rq->fence);
281}
282
283int i915_request_await_object(struct i915_request *to,
284 struct drm_i915_gem_object *obj,
285 bool write);
286int i915_request_await_dma_fence(struct i915_request *rq,
287 struct dma_fence *fence);
288int i915_request_await_execution(struct i915_request *rq,
289 struct dma_fence *fence,
290 void (*hook)(struct i915_request *rq,
291 struct dma_fence *signal));
292
293void i915_request_add(struct i915_request *rq);
294
295bool __i915_request_submit(struct i915_request *request);
296void i915_request_submit(struct i915_request *request);
297
298void i915_request_skip(struct i915_request *request, int error);
299
300void __i915_request_unsubmit(struct i915_request *request);
301void i915_request_unsubmit(struct i915_request *request);
302
303/* Note: part of the intel_breadcrumbs family */
304bool i915_request_enable_breadcrumb(struct i915_request *request);
305void i915_request_cancel_breadcrumb(struct i915_request *request);
306
307long i915_request_wait(struct i915_request *rq,
308 unsigned int flags,
309 long timeout)
310 __attribute__((nonnull(1)));
311#define I915_WAIT_INTERRUPTIBLE BIT(0)
312#define I915_WAIT_LOCKED BIT(1) /* struct_mutex held, handle GPU reset */
313#define I915_WAIT_PRIORITY BIT(2) /* small priority bump for the request */
314#define I915_WAIT_ALL BIT(3) /* used by i915_gem_object_wait() */
315#define I915_WAIT_FOR_IDLE_BOOST BIT(4)
316
317static inline bool i915_request_signaled(const struct i915_request *rq)
318{
319 /* The request may live longer than its HWSP, so check flags first! */
320 return test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &rq->fence.flags);
321}
322
323static inline bool i915_request_is_active(const struct i915_request *rq)
324{
325 return test_bit(I915_FENCE_FLAG_ACTIVE, &rq->fence.flags);
326}
327
328/**
329 * Returns true if seq1 is later than seq2.
330 */
331static inline bool i915_seqno_passed(u32 seq1, u32 seq2)
332{
333 return (s32)(seq1 - seq2) >= 0;
334}
335
336static inline u32 __hwsp_seqno(const struct i915_request *rq)
337{
338 return READ_ONCE(*rq->hwsp_seqno);
339}
340
341/**
342 * hwsp_seqno - the current breadcrumb value in the HW status page
343 * @rq: the request, to chase the relevant HW status page
344 *
345 * The emphasis in naming here is that hwsp_seqno() is not a property of the
346 * request, but an indication of the current HW state (associated with this
347 * request). Its value will change as the GPU executes more requests.
348 *
349 * Returns the current breadcrumb value in the associated HW status page (or
350 * the local timeline's equivalent) for this request. The request itself
351 * has the associated breadcrumb value of rq->fence.seqno, when the HW
352 * status page has that breadcrumb or later, this request is complete.
353 */
354static inline u32 hwsp_seqno(const struct i915_request *rq)
355{
356 u32 seqno;
357
358 rcu_read_lock(); /* the HWSP may be freed at runtime */
359 seqno = __hwsp_seqno(rq);
360 rcu_read_unlock();
361
362 return seqno;
363}
364
365static inline bool __i915_request_has_started(const struct i915_request *rq)
366{
367 return i915_seqno_passed(hwsp_seqno(rq), rq->fence.seqno - 1);
368}
369
370/**
371 * i915_request_started - check if the request has begun being executed
372 * @rq: the request
373 *
374 * If the timeline is not using initial breadcrumbs, a request is
375 * considered started if the previous request on its timeline (i.e.
376 * context) has been signaled.
377 *
378 * If the timeline is using semaphores, it will also be emitting an
379 * "initial breadcrumb" after the semaphores are complete and just before
380 * it began executing the user payload. A request can therefore be active
381 * on the HW and not yet started as it is still busywaiting on its
382 * dependencies (via HW semaphores).
383 *
384 * If the request has started, its dependencies will have been signaled
385 * (either by fences or by semaphores) and it will have begun processing
386 * the user payload.
387 *
388 * However, even if a request has started, it may have been preempted and
389 * so no longer active, or it may have already completed.
390 *
391 * See also i915_request_is_active().
392 *
393 * Returns true if the request has begun executing the user payload, or
394 * has completed:
395 */
396static inline bool i915_request_started(const struct i915_request *rq)
397{
398 if (i915_request_signaled(rq))
399 return true;
400
401 /* Remember: started but may have since been preempted! */
402 return __i915_request_has_started(rq);
403}
404
405/**
406 * i915_request_is_running - check if the request may actually be executing
407 * @rq: the request
408 *
409 * Returns true if the request is currently submitted to hardware, has passed
410 * its start point (i.e. the context is setup and not busywaiting). Note that
411 * it may no longer be running by the time the function returns!
412 */
413static inline bool i915_request_is_running(const struct i915_request *rq)
414{
415 if (!i915_request_is_active(rq))
416 return false;
417
418 return __i915_request_has_started(rq);
419}
420
421static inline bool i915_request_completed(const struct i915_request *rq)
422{
423 if (i915_request_signaled(rq))
424 return true;
425
426 return i915_seqno_passed(hwsp_seqno(rq), rq->fence.seqno);
427}
428
429static inline void i915_request_mark_complete(struct i915_request *rq)
430{
431 rq->hwsp_seqno = (u32 *)&rq->fence.seqno; /* decouple from HWSP */
432}
433
434static inline bool i915_request_has_waitboost(const struct i915_request *rq)
435{
436 return rq->flags & I915_REQUEST_WAITBOOST;
437}
438
439static inline bool i915_request_has_nopreempt(const struct i915_request *rq)
440{
441 /* Preemption should only be disabled very rarely */
442 return unlikely(rq->flags & I915_REQUEST_NOPREEMPT);
443}
444
445bool i915_retire_requests(struct drm_i915_private *i915);
446
447#endif /* I915_REQUEST_H */
1/*
2 * Copyright © 2008-2018 Intel Corporation
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
21 * IN THE SOFTWARE.
22 *
23 */
24
25#ifndef I915_REQUEST_H
26#define I915_REQUEST_H
27
28#include <linux/dma-fence.h>
29
30#include "i915_gem.h"
31#include "i915_sw_fence.h"
32
33#include <uapi/drm/i915_drm.h>
34
35struct drm_file;
36struct drm_i915_gem_object;
37struct i915_request;
38
39struct intel_wait {
40 struct rb_node node;
41 struct task_struct *tsk;
42 struct i915_request *request;
43 u32 seqno;
44};
45
46struct intel_signal_node {
47 struct intel_wait wait;
48 struct list_head link;
49};
50
51struct i915_dependency {
52 struct i915_priotree *signaler;
53 struct list_head signal_link;
54 struct list_head wait_link;
55 struct list_head dfs_link;
56 unsigned long flags;
57#define I915_DEPENDENCY_ALLOC BIT(0)
58};
59
60/*
61 * "People assume that time is a strict progression of cause to effect, but
62 * actually, from a nonlinear, non-subjective viewpoint, it's more like a big
63 * ball of wibbly-wobbly, timey-wimey ... stuff." -The Doctor, 2015
64 *
65 * Requests exist in a complex web of interdependencies. Each request
66 * has to wait for some other request to complete before it is ready to be run
67 * (e.g. we have to wait until the pixels have been rendering into a texture
68 * before we can copy from it). We track the readiness of a request in terms
69 * of fences, but we also need to keep the dependency tree for the lifetime
70 * of the request (beyond the life of an individual fence). We use the tree
71 * at various points to reorder the requests whilst keeping the requests
72 * in order with respect to their various dependencies.
73 */
74struct i915_priotree {
75 struct list_head signalers_list; /* those before us, we depend upon */
76 struct list_head waiters_list; /* those after us, they depend upon us */
77 struct list_head link;
78 int priority;
79};
80
81enum {
82 I915_PRIORITY_MIN = I915_CONTEXT_MIN_USER_PRIORITY - 1,
83 I915_PRIORITY_NORMAL = I915_CONTEXT_DEFAULT_PRIORITY,
84 I915_PRIORITY_MAX = I915_CONTEXT_MAX_USER_PRIORITY + 1,
85
86 I915_PRIORITY_INVALID = INT_MIN
87};
88
89struct i915_capture_list {
90 struct i915_capture_list *next;
91 struct i915_vma *vma;
92};
93
94/**
95 * Request queue structure.
96 *
97 * The request queue allows us to note sequence numbers that have been emitted
98 * and may be associated with active buffers to be retired.
99 *
100 * By keeping this list, we can avoid having to do questionable sequence
101 * number comparisons on buffer last_read|write_seqno. It also allows an
102 * emission time to be associated with the request for tracking how far ahead
103 * of the GPU the submission is.
104 *
105 * When modifying this structure be very aware that we perform a lockless
106 * RCU lookup of it that may race against reallocation of the struct
107 * from the slab freelist. We intentionally do not zero the structure on
108 * allocation so that the lookup can use the dangling pointers (and is
109 * cogniscent that those pointers may be wrong). Instead, everything that
110 * needs to be initialised must be done so explicitly.
111 *
112 * The requests are reference counted.
113 */
114struct i915_request {
115 struct dma_fence fence;
116 spinlock_t lock;
117
118 /** On Which ring this request was generated */
119 struct drm_i915_private *i915;
120
121 /**
122 * Context and ring buffer related to this request
123 * Contexts are refcounted, so when this request is associated with a
124 * context, we must increment the context's refcount, to guarantee that
125 * it persists while any request is linked to it. Requests themselves
126 * are also refcounted, so the request will only be freed when the last
127 * reference to it is dismissed, and the code in
128 * i915_request_free() will then decrement the refcount on the
129 * context.
130 */
131 struct i915_gem_context *ctx;
132 struct intel_engine_cs *engine;
133 struct intel_ring *ring;
134 struct intel_timeline *timeline;
135 struct intel_signal_node signaling;
136
137 /*
138 * Fences for the various phases in the request's lifetime.
139 *
140 * The submit fence is used to await upon all of the request's
141 * dependencies. When it is signaled, the request is ready to run.
142 * It is used by the driver to then queue the request for execution.
143 */
144 struct i915_sw_fence submit;
145 wait_queue_entry_t submitq;
146 wait_queue_head_t execute;
147
148 /*
149 * A list of everyone we wait upon, and everyone who waits upon us.
150 * Even though we will not be submitted to the hardware before the
151 * submit fence is signaled (it waits for all external events as well
152 * as our own requests), the scheduler still needs to know the
153 * dependency tree for the lifetime of the request (from execbuf
154 * to retirement), i.e. bidirectional dependency information for the
155 * request not tied to individual fences.
156 */
157 struct i915_priotree priotree;
158 struct i915_dependency dep;
159
160 /**
161 * GEM sequence number associated with this request on the
162 * global execution timeline. It is zero when the request is not
163 * on the HW queue (i.e. not on the engine timeline list).
164 * Its value is guarded by the timeline spinlock.
165 */
166 u32 global_seqno;
167
168 /** Position in the ring of the start of the request */
169 u32 head;
170
171 /**
172 * Position in the ring of the start of the postfix.
173 * This is required to calculate the maximum available ring space
174 * without overwriting the postfix.
175 */
176 u32 postfix;
177
178 /** Position in the ring of the end of the whole request */
179 u32 tail;
180
181 /** Position in the ring of the end of any workarounds after the tail */
182 u32 wa_tail;
183
184 /** Preallocate space in the ring for the emitting the request */
185 u32 reserved_space;
186
187 /** Batch buffer related to this request if any (used for
188 * error state dump only).
189 */
190 struct i915_vma *batch;
191 /**
192 * Additional buffers requested by userspace to be captured upon
193 * a GPU hang. The vma/obj on this list are protected by their
194 * active reference - all objects on this list must also be
195 * on the active_list (of their final request).
196 */
197 struct i915_capture_list *capture_list;
198 struct list_head active_list;
199
200 /** Time at which this request was emitted, in jiffies. */
201 unsigned long emitted_jiffies;
202
203 bool waitboost;
204
205 /** engine->request_list entry for this request */
206 struct list_head link;
207
208 /** ring->request_list entry for this request */
209 struct list_head ring_link;
210
211 struct drm_i915_file_private *file_priv;
212 /** file_priv list entry for this request */
213 struct list_head client_link;
214};
215
216#define I915_FENCE_GFP (GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN)
217
218extern const struct dma_fence_ops i915_fence_ops;
219
220static inline bool dma_fence_is_i915(const struct dma_fence *fence)
221{
222 return fence->ops == &i915_fence_ops;
223}
224
225struct i915_request * __must_check
226i915_request_alloc(struct intel_engine_cs *engine,
227 struct i915_gem_context *ctx);
228void i915_request_retire_upto(struct i915_request *rq);
229
230static inline struct i915_request *
231to_request(struct dma_fence *fence)
232{
233 /* We assume that NULL fence/request are interoperable */
234 BUILD_BUG_ON(offsetof(struct i915_request, fence) != 0);
235 GEM_BUG_ON(fence && !dma_fence_is_i915(fence));
236 return container_of(fence, struct i915_request, fence);
237}
238
239static inline struct i915_request *
240i915_request_get(struct i915_request *rq)
241{
242 return to_request(dma_fence_get(&rq->fence));
243}
244
245static inline struct i915_request *
246i915_request_get_rcu(struct i915_request *rq)
247{
248 return to_request(dma_fence_get_rcu(&rq->fence));
249}
250
251static inline void
252i915_request_put(struct i915_request *rq)
253{
254 dma_fence_put(&rq->fence);
255}
256
257/**
258 * i915_request_global_seqno - report the current global seqno
259 * @request - the request
260 *
261 * A request is assigned a global seqno only when it is on the hardware
262 * execution queue. The global seqno can be used to maintain a list of
263 * requests on the same engine in retirement order, for example for
264 * constructing a priority queue for waiting. Prior to its execution, or
265 * if it is subsequently removed in the event of preemption, its global
266 * seqno is zero. As both insertion and removal from the execution queue
267 * may operate in IRQ context, it is not guarded by the usual struct_mutex
268 * BKL. Instead those relying on the global seqno must be prepared for its
269 * value to change between reads. Only when the request is complete can
270 * the global seqno be stable (due to the memory barriers on submitting
271 * the commands to the hardware to write the breadcrumb, if the HWS shows
272 * that it has passed the global seqno and the global seqno is unchanged
273 * after the read, it is indeed complete).
274 */
275static u32
276i915_request_global_seqno(const struct i915_request *request)
277{
278 return READ_ONCE(request->global_seqno);
279}
280
281int i915_request_await_object(struct i915_request *to,
282 struct drm_i915_gem_object *obj,
283 bool write);
284int i915_request_await_dma_fence(struct i915_request *rq,
285 struct dma_fence *fence);
286
287void __i915_request_add(struct i915_request *rq, bool flush_caches);
288#define i915_request_add(rq) \
289 __i915_request_add(rq, false)
290
291void __i915_request_submit(struct i915_request *request);
292void i915_request_submit(struct i915_request *request);
293
294void __i915_request_unsubmit(struct i915_request *request);
295void i915_request_unsubmit(struct i915_request *request);
296
297long i915_request_wait(struct i915_request *rq,
298 unsigned int flags,
299 long timeout)
300 __attribute__((nonnull(1)));
301#define I915_WAIT_INTERRUPTIBLE BIT(0)
302#define I915_WAIT_LOCKED BIT(1) /* struct_mutex held, handle GPU reset */
303#define I915_WAIT_ALL BIT(2) /* used by i915_gem_object_wait() */
304
305static inline u32 intel_engine_get_seqno(struct intel_engine_cs *engine);
306
307/**
308 * Returns true if seq1 is later than seq2.
309 */
310static inline bool i915_seqno_passed(u32 seq1, u32 seq2)
311{
312 return (s32)(seq1 - seq2) >= 0;
313}
314
315static inline bool
316__i915_request_completed(const struct i915_request *rq, u32 seqno)
317{
318 GEM_BUG_ON(!seqno);
319 return i915_seqno_passed(intel_engine_get_seqno(rq->engine), seqno) &&
320 seqno == i915_request_global_seqno(rq);
321}
322
323static inline bool i915_request_completed(const struct i915_request *rq)
324{
325 u32 seqno;
326
327 seqno = i915_request_global_seqno(rq);
328 if (!seqno)
329 return false;
330
331 return __i915_request_completed(rq, seqno);
332}
333
334static inline bool i915_request_started(const struct i915_request *rq)
335{
336 u32 seqno;
337
338 seqno = i915_request_global_seqno(rq);
339 if (!seqno)
340 return false;
341
342 return i915_seqno_passed(intel_engine_get_seqno(rq->engine),
343 seqno - 1);
344}
345
346static inline bool i915_priotree_signaled(const struct i915_priotree *pt)
347{
348 const struct i915_request *rq =
349 container_of(pt, const struct i915_request, priotree);
350
351 return i915_request_completed(rq);
352}
353
354void i915_retire_requests(struct drm_i915_private *i915);
355
356/*
357 * We treat requests as fences. This is not be to confused with our
358 * "fence registers" but pipeline synchronisation objects ala GL_ARB_sync.
359 * We use the fences to synchronize access from the CPU with activity on the
360 * GPU, for example, we should not rewrite an object's PTE whilst the GPU
361 * is reading them. We also track fences at a higher level to provide
362 * implicit synchronisation around GEM objects, e.g. set-domain will wait
363 * for outstanding GPU rendering before marking the object ready for CPU
364 * access, or a pageflip will wait until the GPU is complete before showing
365 * the frame on the scanout.
366 *
367 * In order to use a fence, the object must track the fence it needs to
368 * serialise with. For example, GEM objects want to track both read and
369 * write access so that we can perform concurrent read operations between
370 * the CPU and GPU engines, as well as waiting for all rendering to
371 * complete, or waiting for the last GPU user of a "fence register". The
372 * object then embeds a #i915_gem_active to track the most recent (in
373 * retirement order) request relevant for the desired mode of access.
374 * The #i915_gem_active is updated with i915_gem_active_set() to track the
375 * most recent fence request, typically this is done as part of
376 * i915_vma_move_to_active().
377 *
378 * When the #i915_gem_active completes (is retired), it will
379 * signal its completion to the owner through a callback as well as mark
380 * itself as idle (i915_gem_active.request == NULL). The owner
381 * can then perform any action, such as delayed freeing of an active
382 * resource including itself.
383 */
384struct i915_gem_active;
385
386typedef void (*i915_gem_retire_fn)(struct i915_gem_active *,
387 struct i915_request *);
388
389struct i915_gem_active {
390 struct i915_request __rcu *request;
391 struct list_head link;
392 i915_gem_retire_fn retire;
393};
394
395void i915_gem_retire_noop(struct i915_gem_active *,
396 struct i915_request *request);
397
398/**
399 * init_request_active - prepares the activity tracker for use
400 * @active - the active tracker
401 * @func - a callback when then the tracker is retired (becomes idle),
402 * can be NULL
403 *
404 * init_request_active() prepares the embedded @active struct for use as
405 * an activity tracker, that is for tracking the last known active request
406 * associated with it. When the last request becomes idle, when it is retired
407 * after completion, the optional callback @func is invoked.
408 */
409static inline void
410init_request_active(struct i915_gem_active *active,
411 i915_gem_retire_fn retire)
412{
413 INIT_LIST_HEAD(&active->link);
414 active->retire = retire ?: i915_gem_retire_noop;
415}
416
417/**
418 * i915_gem_active_set - updates the tracker to watch the current request
419 * @active - the active tracker
420 * @request - the request to watch
421 *
422 * i915_gem_active_set() watches the given @request for completion. Whilst
423 * that @request is busy, the @active reports busy. When that @request is
424 * retired, the @active tracker is updated to report idle.
425 */
426static inline void
427i915_gem_active_set(struct i915_gem_active *active,
428 struct i915_request *request)
429{
430 list_move(&active->link, &request->active_list);
431 rcu_assign_pointer(active->request, request);
432}
433
434/**
435 * i915_gem_active_set_retire_fn - updates the retirement callback
436 * @active - the active tracker
437 * @fn - the routine called when the request is retired
438 * @mutex - struct_mutex used to guard retirements
439 *
440 * i915_gem_active_set_retire_fn() updates the function pointer that
441 * is called when the final request associated with the @active tracker
442 * is retired.
443 */
444static inline void
445i915_gem_active_set_retire_fn(struct i915_gem_active *active,
446 i915_gem_retire_fn fn,
447 struct mutex *mutex)
448{
449 lockdep_assert_held(mutex);
450 active->retire = fn ?: i915_gem_retire_noop;
451}
452
453static inline struct i915_request *
454__i915_gem_active_peek(const struct i915_gem_active *active)
455{
456 /*
457 * Inside the error capture (running with the driver in an unknown
458 * state), we want to bend the rules slightly (a lot).
459 *
460 * Work is in progress to make it safer, in the meantime this keeps
461 * the known issue from spamming the logs.
462 */
463 return rcu_dereference_protected(active->request, 1);
464}
465
466/**
467 * i915_gem_active_raw - return the active request
468 * @active - the active tracker
469 *
470 * i915_gem_active_raw() returns the current request being tracked, or NULL.
471 * It does not obtain a reference on the request for the caller, so the caller
472 * must hold struct_mutex.
473 */
474static inline struct i915_request *
475i915_gem_active_raw(const struct i915_gem_active *active, struct mutex *mutex)
476{
477 return rcu_dereference_protected(active->request,
478 lockdep_is_held(mutex));
479}
480
481/**
482 * i915_gem_active_peek - report the active request being monitored
483 * @active - the active tracker
484 *
485 * i915_gem_active_peek() returns the current request being tracked if
486 * still active, or NULL. It does not obtain a reference on the request
487 * for the caller, so the caller must hold struct_mutex.
488 */
489static inline struct i915_request *
490i915_gem_active_peek(const struct i915_gem_active *active, struct mutex *mutex)
491{
492 struct i915_request *request;
493
494 request = i915_gem_active_raw(active, mutex);
495 if (!request || i915_request_completed(request))
496 return NULL;
497
498 return request;
499}
500
501/**
502 * i915_gem_active_get - return a reference to the active request
503 * @active - the active tracker
504 *
505 * i915_gem_active_get() returns a reference to the active request, or NULL
506 * if the active tracker is idle. The caller must hold struct_mutex.
507 */
508static inline struct i915_request *
509i915_gem_active_get(const struct i915_gem_active *active, struct mutex *mutex)
510{
511 return i915_request_get(i915_gem_active_peek(active, mutex));
512}
513
514/**
515 * __i915_gem_active_get_rcu - return a reference to the active request
516 * @active - the active tracker
517 *
518 * __i915_gem_active_get() returns a reference to the active request, or NULL
519 * if the active tracker is idle. The caller must hold the RCU read lock, but
520 * the returned pointer is safe to use outside of RCU.
521 */
522static inline struct i915_request *
523__i915_gem_active_get_rcu(const struct i915_gem_active *active)
524{
525 /*
526 * Performing a lockless retrieval of the active request is super
527 * tricky. SLAB_TYPESAFE_BY_RCU merely guarantees that the backing
528 * slab of request objects will not be freed whilst we hold the
529 * RCU read lock. It does not guarantee that the request itself
530 * will not be freed and then *reused*. Viz,
531 *
532 * Thread A Thread B
533 *
534 * rq = active.request
535 * retire(rq) -> free(rq);
536 * (rq is now first on the slab freelist)
537 * active.request = NULL
538 *
539 * rq = new submission on a new object
540 * ref(rq)
541 *
542 * To prevent the request from being reused whilst the caller
543 * uses it, we take a reference like normal. Whilst acquiring
544 * the reference we check that it is not in a destroyed state
545 * (refcnt == 0). That prevents the request being reallocated
546 * whilst the caller holds on to it. To check that the request
547 * was not reallocated as we acquired the reference we have to
548 * check that our request remains the active request across
549 * the lookup, in the same manner as a seqlock. The visibility
550 * of the pointer versus the reference counting is controlled
551 * by using RCU barriers (rcu_dereference and rcu_assign_pointer).
552 *
553 * In the middle of all that, we inspect whether the request is
554 * complete. Retiring is lazy so the request may be completed long
555 * before the active tracker is updated. Querying whether the
556 * request is complete is far cheaper (as it involves no locked
557 * instructions setting cachelines to exclusive) than acquiring
558 * the reference, so we do it first. The RCU read lock ensures the
559 * pointer dereference is valid, but does not ensure that the
560 * seqno nor HWS is the right one! However, if the request was
561 * reallocated, that means the active tracker's request was complete.
562 * If the new request is also complete, then both are and we can
563 * just report the active tracker is idle. If the new request is
564 * incomplete, then we acquire a reference on it and check that
565 * it remained the active request.
566 *
567 * It is then imperative that we do not zero the request on
568 * reallocation, so that we can chase the dangling pointers!
569 * See i915_request_alloc().
570 */
571 do {
572 struct i915_request *request;
573
574 request = rcu_dereference(active->request);
575 if (!request || i915_request_completed(request))
576 return NULL;
577
578 /*
579 * An especially silly compiler could decide to recompute the
580 * result of i915_request_completed, more specifically
581 * re-emit the load for request->fence.seqno. A race would catch
582 * a later seqno value, which could flip the result from true to
583 * false. Which means part of the instructions below might not
584 * be executed, while later on instructions are executed. Due to
585 * barriers within the refcounting the inconsistency can't reach
586 * past the call to i915_request_get_rcu, but not executing
587 * that while still executing i915_request_put() creates
588 * havoc enough. Prevent this with a compiler barrier.
589 */
590 barrier();
591
592 request = i915_request_get_rcu(request);
593
594 /*
595 * What stops the following rcu_access_pointer() from occurring
596 * before the above i915_request_get_rcu()? If we were
597 * to read the value before pausing to get the reference to
598 * the request, we may not notice a change in the active
599 * tracker.
600 *
601 * The rcu_access_pointer() is a mere compiler barrier, which
602 * means both the CPU and compiler are free to perform the
603 * memory read without constraint. The compiler only has to
604 * ensure that any operations after the rcu_access_pointer()
605 * occur afterwards in program order. This means the read may
606 * be performed earlier by an out-of-order CPU, or adventurous
607 * compiler.
608 *
609 * The atomic operation at the heart of
610 * i915_request_get_rcu(), see dma_fence_get_rcu(), is
611 * atomic_inc_not_zero() which is only a full memory barrier
612 * when successful. That is, if i915_request_get_rcu()
613 * returns the request (and so with the reference counted
614 * incremented) then the following read for rcu_access_pointer()
615 * must occur after the atomic operation and so confirm
616 * that this request is the one currently being tracked.
617 *
618 * The corresponding write barrier is part of
619 * rcu_assign_pointer().
620 */
621 if (!request || request == rcu_access_pointer(active->request))
622 return rcu_pointer_handoff(request);
623
624 i915_request_put(request);
625 } while (1);
626}
627
628/**
629 * i915_gem_active_get_unlocked - return a reference to the active request
630 * @active - the active tracker
631 *
632 * i915_gem_active_get_unlocked() returns a reference to the active request,
633 * or NULL if the active tracker is idle. The reference is obtained under RCU,
634 * so no locking is required by the caller.
635 *
636 * The reference should be freed with i915_request_put().
637 */
638static inline struct i915_request *
639i915_gem_active_get_unlocked(const struct i915_gem_active *active)
640{
641 struct i915_request *request;
642
643 rcu_read_lock();
644 request = __i915_gem_active_get_rcu(active);
645 rcu_read_unlock();
646
647 return request;
648}
649
650/**
651 * i915_gem_active_isset - report whether the active tracker is assigned
652 * @active - the active tracker
653 *
654 * i915_gem_active_isset() returns true if the active tracker is currently
655 * assigned to a request. Due to the lazy retiring, that request may be idle
656 * and this may report stale information.
657 */
658static inline bool
659i915_gem_active_isset(const struct i915_gem_active *active)
660{
661 return rcu_access_pointer(active->request);
662}
663
664/**
665 * i915_gem_active_wait - waits until the request is completed
666 * @active - the active request on which to wait
667 * @flags - how to wait
668 * @timeout - how long to wait at most
669 * @rps - userspace client to charge for a waitboost
670 *
671 * i915_gem_active_wait() waits until the request is completed before
672 * returning, without requiring any locks to be held. Note that it does not
673 * retire any requests before returning.
674 *
675 * This function relies on RCU in order to acquire the reference to the active
676 * request without holding any locks. See __i915_gem_active_get_rcu() for the
677 * glory details on how that is managed. Once the reference is acquired, we
678 * can then wait upon the request, and afterwards release our reference,
679 * free of any locking.
680 *
681 * This function wraps i915_request_wait(), see it for the full details on
682 * the arguments.
683 *
684 * Returns 0 if successful, or a negative error code.
685 */
686static inline int
687i915_gem_active_wait(const struct i915_gem_active *active, unsigned int flags)
688{
689 struct i915_request *request;
690 long ret = 0;
691
692 request = i915_gem_active_get_unlocked(active);
693 if (request) {
694 ret = i915_request_wait(request, flags, MAX_SCHEDULE_TIMEOUT);
695 i915_request_put(request);
696 }
697
698 return ret < 0 ? ret : 0;
699}
700
701/**
702 * i915_gem_active_retire - waits until the request is retired
703 * @active - the active request on which to wait
704 *
705 * i915_gem_active_retire() waits until the request is completed,
706 * and then ensures that at least the retirement handler for this
707 * @active tracker is called before returning. If the @active
708 * tracker is idle, the function returns immediately.
709 */
710static inline int __must_check
711i915_gem_active_retire(struct i915_gem_active *active,
712 struct mutex *mutex)
713{
714 struct i915_request *request;
715 long ret;
716
717 request = i915_gem_active_raw(active, mutex);
718 if (!request)
719 return 0;
720
721 ret = i915_request_wait(request,
722 I915_WAIT_INTERRUPTIBLE | I915_WAIT_LOCKED,
723 MAX_SCHEDULE_TIMEOUT);
724 if (ret < 0)
725 return ret;
726
727 list_del_init(&active->link);
728 RCU_INIT_POINTER(active->request, NULL);
729
730 active->retire(active, request);
731
732 return 0;
733}
734
735#define for_each_active(mask, idx) \
736 for (; mask ? idx = ffs(mask) - 1, 1 : 0; mask &= ~BIT(idx))
737
738#endif /* I915_REQUEST_H */