[PATCH v6 3/4] drm/i915: Update error capture code to avoid using the current vma state

Thomas Hellström thomas.hellstrom at linux.intel.com
Mon Nov 8 17:45:46 UTC 2021


With asynchronous migrations, the vma state may be several migrations
ahead of the state that matches the request we're capturing.
Address that by introducing an i915_vma_snapshot structure that
can be used to snapshot relevant state at request submission.
In order to make sure we access the correct memory, the snapshots take
references on relevant sg-tables and memory regions.

Also move the capture list allocation out of the fence signaling
critical path and use the CONFIG_DRM_I915_CAPTURE_ERROR define to
avoid compiling in members and functions used for error capture
when they're not used.

Finally, Introduce lockdep annotation.

v4:
- Break out the capture allocation mode change to a separate patch.
v5:
- Fix compilation error in the !CONFIG_DRM_I915_CAPTURE_ERROR case
  (kernel test robot)
v6:
- Use #if IS_ENABLED() instead of #ifdef to match driver style.
- Move yet another change of allocation mode to the separate patch.
- Commit message rework due to patch reordering.

Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
---
 drivers/gpu/drm/i915/Makefile                 |   1 +
 .../gpu/drm/i915/gem/i915_gem_execbuffer.c    | 135 +++++++++++---
 drivers/gpu/drm/i915/gt/intel_engine_cs.c     |   8 +-
 drivers/gpu/drm/i915/i915_gpu_error.c         | 176 +++++++++++++-----
 drivers/gpu/drm/i915/i915_request.c           |  63 +++++--
 drivers/gpu/drm/i915/i915_request.h           |  20 +-
 drivers/gpu/drm/i915/i915_vma_snapshot.c      | 137 ++++++++++++++
 drivers/gpu/drm/i915/i915_vma_snapshot.h      | 112 +++++++++++
 8 files changed, 557 insertions(+), 95 deletions(-)
 create mode 100644 drivers/gpu/drm/i915/i915_vma_snapshot.c
 create mode 100644 drivers/gpu/drm/i915/i915_vma_snapshot.h

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 7d0d0b814670..b4372e0a802f 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -174,6 +174,7 @@ i915-y += \
 	  i915_trace_points.o \
 	  i915_ttm_buddy_manager.o \
 	  i915_vma.o \
+	  i915_vma_snapshot.o \
 	  intel_wopcm.o
 
 # general-purpose microcontroller (GuC) support
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index ea5b7b2a4d70..ddca899f2396 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -29,6 +29,7 @@
 #include "i915_gem_ioctls.h"
 #include "i915_trace.h"
 #include "i915_user_extensions.h"
+#include "i915_vma_snapshot.h"
 
 struct eb_vma {
 	struct i915_vma *vma;
@@ -307,11 +308,15 @@ struct i915_execbuffer {
 
 	struct eb_fence *fences;
 	unsigned long num_fences;
+#if IS_ENABLED(CONFIG_DRM_I915_CAPTURE_ERROR)
+	struct i915_capture_list *capture_lists[MAX_ENGINE_INSTANCE + 1];
+#endif
 };
 
 static int eb_parse(struct i915_execbuffer *eb);
 static int eb_pin_engine(struct i915_execbuffer *eb, bool throttle);
 static void eb_unpin_engine(struct i915_execbuffer *eb);
+static void eb_capture_release(struct i915_execbuffer *eb);
 
 static inline bool eb_use_cmdparser(const struct i915_execbuffer *eb)
 {
@@ -1054,6 +1059,7 @@ static void eb_release_vmas(struct i915_execbuffer *eb, bool final)
 			i915_vma_put(vma);
 	}
 
+	eb_capture_release(eb);
 	eb_unpin_engine(eb);
 }
 
@@ -1891,36 +1897,113 @@ eb_find_first_request_added(struct i915_execbuffer *eb)
 	return NULL;
 }
 
-static int eb_move_to_gpu(struct i915_execbuffer *eb)
+#if IS_ENABLED(CONFIG_DRM_I915_CAPTURE_ERROR)
+
+/* Stage with GFP_KERNEL allocations before we enter the signaling critical path */
+static void eb_capture_stage(struct i915_execbuffer *eb)
 {
 	const unsigned int count = eb->buffer_count;
-	unsigned int i = count;
-	int err = 0, j;
+	unsigned int i = count, j;
+	struct i915_vma_snapshot *vsnap;
 
 	while (i--) {
 		struct eb_vma *ev = &eb->vma[i];
 		struct i915_vma *vma = ev->vma;
 		unsigned int flags = ev->flags;
-		struct drm_i915_gem_object *obj = vma->obj;
 
-		assert_vma_held(vma);
+		if (!(flags & EXEC_OBJECT_CAPTURE))
+			continue;
 
-		if (flags & EXEC_OBJECT_CAPTURE) {
+		vsnap = i915_vma_snapshot_alloc(GFP_KERNEL);
+		if (!vsnap)
+			continue;
+
+		i915_vma_snapshot_init(vsnap, vma, "user");
+		for_each_batch_create_order(eb, j) {
 			struct i915_capture_list *capture;
 
-			for_each_batch_create_order(eb, j) {
-				if (!eb->requests[j])
-					break;
+			capture = kmalloc(sizeof(*capture), GFP_KERNEL);
+			if (!capture)
+				continue;
 
-				capture = kmalloc(sizeof(*capture), GFP_KERNEL);
-				if (capture) {
-					capture->next =
-						eb->requests[j]->capture_list;
-					capture->vma = vma;
-					eb->requests[j]->capture_list = capture;
-				}
-			}
+			capture->next = eb->capture_lists[j];
+			capture->vma_snapshot = i915_vma_snapshot_get(vsnap);
+			eb->capture_lists[j] = capture;
+		}
+		i915_vma_snapshot_put(vsnap);
+	}
+}
+
+/* Commit once we're in the critical path */
+static void eb_capture_commit(struct i915_execbuffer *eb)
+{
+	unsigned int j;
+
+	for_each_batch_create_order(eb, j) {
+		struct i915_request *rq = eb->requests[j];
+
+		if (!rq)
+			break;
+
+		rq->capture_list = eb->capture_lists[j];
+		eb->capture_lists[j] = NULL;
+	}
+}
+
+/*
+ * Release anything that didn't get committed due to errors.
+ * The capture_list will otherwise be freed at request retire.
+ */
+static void eb_capture_release(struct i915_execbuffer *eb)
+{
+	unsigned int j;
+
+	for_each_batch_create_order(eb, j) {
+		if (eb->capture_lists[j]) {
+			i915_request_free_capture_list(eb->capture_lists[j]);
+			eb->capture_lists[j] = NULL;
 		}
+	}
+}
+
+static void eb_capture_list_clear(struct i915_execbuffer *eb)
+{
+	memset(eb->capture_lists, 0, sizeof(eb->capture_lists));
+}
+
+#else
+
+static void eb_capture_stage(struct i915_execbuffer *eb)
+{
+}
+
+static void eb_capture_commit(struct i915_execbuffer *eb)
+{
+}
+
+static void eb_capture_release(struct i915_execbuffer *eb)
+{
+}
+
+static void eb_capture_list_clear(struct i915_execbuffer *eb)
+{
+}
+
+#endif
+
+static int eb_move_to_gpu(struct i915_execbuffer *eb)
+{
+	const unsigned int count = eb->buffer_count;
+	unsigned int i = count;
+	int err = 0, j;
+
+	while (i--) {
+		struct eb_vma *ev = &eb->vma[i];
+		struct i915_vma *vma = ev->vma;
+		unsigned int flags = ev->flags;
+		struct drm_i915_gem_object *obj = vma->obj;
+
+		assert_vma_held(vma);
 
 		/*
 		 * If the GPU is not _reading_ through the CPU cache, we need
@@ -2001,6 +2084,8 @@ static int eb_move_to_gpu(struct i915_execbuffer *eb)
 
 	/* Unconditionally flush any chipset caches (for streaming writes). */
 	intel_gt_chipset_flush(eb->gt);
+	eb_capture_commit(eb);
+
 	return 0;
 
 err_skip:
@@ -3143,13 +3228,14 @@ eb_requests_create(struct i915_execbuffer *eb, struct dma_fence *in_fence,
 		}
 
 		/*
-		 * Whilst this request exists, batch_obj will be on the
-		 * active_list, and so will hold the active reference. Only when
-		 * this request is retired will the batch_obj be moved onto
-		 * the inactive_list and lose its active reference. Hence we do
-		 * not need to explicitly hold another reference here.
+		 * Not really on stack, but we don't want to call
+		 * kfree on the batch_snapshot when we put it, so use the
+		 * _onstack interface.
 		 */
-		eb->requests[i]->batch = eb->batches[i]->vma;
+		if (eb->batches[i]->vma)
+			i915_vma_snapshot_init_onstack(&eb->requests[i]->batch_snapshot,
+						       eb->batches[i]->vma,
+						       "batch");
 		if (eb->batch_pool) {
 			GEM_BUG_ON(intel_context_is_parallel(eb->context));
 			intel_gt_buffer_pool_mark_active(eb->batch_pool,
@@ -3198,6 +3284,8 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 	eb.fences = NULL;
 	eb.num_fences = 0;
 
+	eb_capture_list_clear(&eb);
+
 	memset(eb.requests, 0, sizeof(struct i915_request *) *
 	       ARRAY_SIZE(eb.requests));
 	eb.composite_fence = NULL;
@@ -3284,6 +3372,7 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 	}
 
 	ww_acquire_done(&eb.ww.ctx);
+	eb_capture_stage(&eb);
 
 	out_fence = eb_requests_create(&eb, in_fence, out_fence_fd);
 	if (IS_ERR(out_fence)) {
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index 332756036007..f2ccd5b53d42 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -1676,14 +1676,18 @@ static void intel_engine_print_registers(struct intel_engine_cs *engine,
 
 static void print_request_ring(struct drm_printer *m, struct i915_request *rq)
 {
+	struct i915_vma_snapshot *vsnap = &rq->batch_snapshot;
 	void *ring;
 	int size;
 
+	if (!i915_vma_snapshot_present(vsnap))
+		vsnap = NULL;
+
 	drm_printf(m,
 		   "[head %04x, postfix %04x, tail %04x, batch 0x%08x_%08x]:\n",
 		   rq->head, rq->postfix, rq->tail,
-		   rq->batch ? upper_32_bits(rq->batch->node.start) : ~0u,
-		   rq->batch ? lower_32_bits(rq->batch->node.start) : ~0u);
+		   vsnap ? upper_32_bits(vsnap->gtt_offset) : ~0u,
+		   vsnap ? lower_32_bits(vsnap->gtt_offset) : ~0u);
 
 	size = rq->tail - rq->head;
 	if (rq->tail < rq->head)
diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index b1e4ce0f798f..c61f9aaa40f9 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -48,6 +48,7 @@
 #include "i915_gpu_error.h"
 #include "i915_memcpy.h"
 #include "i915_scatterlist.h"
+#include "i915_vma_snapshot.h"
 
 #define ALLOW_FAIL (__GFP_KSWAPD_RECLAIM | __GFP_RETRY_MAYFAIL | __GFP_NOWARN)
 #define ATOMIC_MAYFAIL (GFP_ATOMIC | __GFP_NOWARN)
@@ -1012,8 +1013,7 @@ void __i915_gpu_coredump_free(struct kref *error_ref)
 
 static struct i915_vma_coredump *
 i915_vma_coredump_create(const struct intel_gt *gt,
-			 const struct i915_vma *vma,
-			 const char *name,
+			 const struct i915_vma_snapshot *vsnap,
 			 struct i915_vma_compress *compress)
 {
 	struct i915_ggtt *ggtt = gt->ggtt;
@@ -1024,7 +1024,7 @@ i915_vma_coredump_create(const struct intel_gt *gt,
 
 	might_sleep();
 
-	if (!vma || !vma->pages || !compress)
+	if (!vsnap || !vsnap->pages || !compress)
 		return NULL;
 
 	dst = kmalloc(sizeof(*dst), ALLOW_FAIL);
@@ -1037,12 +1037,12 @@ i915_vma_coredump_create(const struct intel_gt *gt,
 	}
 
 	INIT_LIST_HEAD(&dst->page_list);
-	strcpy(dst->name, name);
+	strcpy(dst->name, vsnap->name);
 	dst->next = NULL;
 
-	dst->gtt_offset = vma->node.start;
-	dst->gtt_size = vma->node.size;
-	dst->gtt_page_sizes = vma->page_sizes.gtt;
+	dst->gtt_offset = vsnap->gtt_offset;
+	dst->gtt_size = vsnap->gtt_size;
+	dst->gtt_page_sizes = vsnap->page_sizes;
 	dst->unused = 0;
 
 	ret = -EINVAL;
@@ -1050,7 +1050,7 @@ i915_vma_coredump_create(const struct intel_gt *gt,
 		void __iomem *s;
 		dma_addr_t dma;
 
-		for_each_sgt_daddr(dma, iter, vma->pages) {
+		for_each_sgt_daddr(dma, iter, vsnap->pages) {
 			mutex_lock(&ggtt->error_mutex);
 			ggtt->vm.insert_page(&ggtt->vm, dma, slot,
 					     I915_CACHE_NONE, 0);
@@ -1068,11 +1068,11 @@ i915_vma_coredump_create(const struct intel_gt *gt,
 			if (ret)
 				break;
 		}
-	} else if (__i915_gem_object_is_lmem(vma->obj)) {
-		struct intel_memory_region *mem = vma->obj->mm.region;
+	} else if (vsnap->mr && vsnap->mr->type != INTEL_MEMORY_SYSTEM) {
+		struct intel_memory_region *mem = vsnap->mr;
 		dma_addr_t dma;
 
-		for_each_sgt_daddr(dma, iter, vma->pages) {
+		for_each_sgt_daddr(dma, iter, vsnap->pages) {
 			void __iomem *s;
 
 			s = io_mapping_map_wc(&mem->iomap,
@@ -1088,7 +1088,7 @@ i915_vma_coredump_create(const struct intel_gt *gt,
 	} else {
 		struct page *page;
 
-		for_each_sgt_page(page, iter, vma->pages) {
+		for_each_sgt_page(page, iter, vsnap->pages) {
 			void *s;
 
 			drm_clflush_pages(&page, 1);
@@ -1324,37 +1324,71 @@ static bool record_context(struct i915_gem_context_coredump *e,
 
 struct intel_engine_capture_vma {
 	struct intel_engine_capture_vma *next;
-	struct i915_vma *vma;
+	struct i915_vma_snapshot *vsnap;
 	char name[16];
+	bool lockdep_cookie;
 };
 
 static struct intel_engine_capture_vma *
-capture_vma(struct intel_engine_capture_vma *next,
-	    struct i915_vma *vma,
-	    const char *name,
-	    gfp_t gfp)
+capture_vma_snapshot(struct intel_engine_capture_vma *next,
+		     struct i915_vma_snapshot *vsnap,
+		     gfp_t gfp)
 {
 	struct intel_engine_capture_vma *c;
 
-	if (!vma)
+	if (!i915_vma_snapshot_present(vsnap))
 		return next;
 
 	c = kmalloc(sizeof(*c), gfp);
 	if (!c)
 		return next;
 
-	if (!i915_active_acquire_if_busy(&vma->active)) {
+	if (!i915_vma_snapshot_resource_pin(vsnap, &c->lockdep_cookie)) {
 		kfree(c);
 		return next;
 	}
 
-	strcpy(c->name, name);
-	c->vma = vma; /* reference held while active */
+	strcpy(c->name, vsnap->name);
+	c->vsnap = vsnap;
+	i915_vma_snapshot_get(vsnap);
 
 	c->next = next;
 	return c;
 }
 
+static struct intel_engine_capture_vma *
+capture_vma(struct intel_engine_capture_vma *next,
+	    struct i915_vma *vma,
+	    const char *name,
+	    gfp_t gfp)
+{
+	struct i915_vma_snapshot *vsnap;
+
+	if (!vma)
+		return next;
+
+	/*
+	 * If the vma isn't pinned, then the vma should be snapshotted
+	 * to a struct i915_vma_snapshot at command submission time.
+	 * Not here.
+	 */
+	GEM_WARN_ON(!i915_vma_is_pinned(vma));
+	if (!i915_vma_is_pinned(vma))
+		return next;
+
+	vsnap = i915_vma_snapshot_alloc(gfp);
+	if (!vsnap)
+		return next;
+
+	i915_vma_snapshot_init(vsnap, vma, name);
+	next = capture_vma_snapshot(next, vsnap, gfp);
+
+	/* FIXME: Replace on async unbind. */
+	i915_vma_snapshot_put(vsnap);
+
+	return next;
+}
+
 static struct intel_engine_capture_vma *
 capture_user(struct intel_engine_capture_vma *capture,
 	     const struct i915_request *rq,
@@ -1363,7 +1397,7 @@ capture_user(struct intel_engine_capture_vma *capture,
 	struct i915_capture_list *c;
 
 	for (c = rq->capture_list; c; c = c->next)
-		capture = capture_vma(capture, c->vma, "user", gfp);
+		capture = capture_vma_snapshot(capture, c->vma_snapshot, gfp);
 
 	return capture;
 }
@@ -1377,6 +1411,36 @@ static void add_vma(struct intel_engine_coredump *ee,
 	}
 }
 
+static struct i915_vma_coredump *
+create_vma_coredump(const struct intel_gt *gt, struct i915_vma *vma,
+		    const char *name, struct i915_vma_compress *compress)
+{
+	struct i915_vma_coredump *ret = NULL;
+	struct i915_vma_snapshot tmp;
+	bool lockdep_cookie;
+
+	if (!vma)
+		return NULL;
+
+	i915_vma_snapshot_init_onstack(&tmp, vma, name);
+	if (i915_vma_snapshot_resource_pin(&tmp, &lockdep_cookie)) {
+		ret = i915_vma_coredump_create(gt, &tmp, compress);
+		i915_vma_snapshot_resource_unpin(&tmp, lockdep_cookie);
+	}
+	i915_vma_snapshot_put_onstack(&tmp);
+
+	return ret;
+}
+
+static void add_vma_coredump(struct intel_engine_coredump *ee,
+			     const struct intel_gt *gt,
+			     struct i915_vma *vma,
+			     const char *name,
+			     struct i915_vma_compress *compress)
+{
+	add_vma(ee, create_vma_coredump(gt, vma, name, compress));
+}
+
 struct intel_engine_coredump *
 intel_engine_coredump_alloc(struct intel_engine_cs *engine, gfp_t gfp)
 {
@@ -1410,7 +1474,7 @@ intel_engine_coredump_add_request(struct intel_engine_coredump *ee,
 	 * as the simplest method to avoid being overwritten
 	 * by userspace.
 	 */
-	vma = capture_vma(vma, rq->batch, "batch", gfp);
+	vma = capture_vma_snapshot(vma, &rq->batch_snapshot, gfp);
 	vma = capture_user(vma, rq, gfp);
 	vma = capture_vma(vma, rq->ring->vma, "ring", gfp);
 	vma = capture_vma(vma, rq->context->state, "HW context", gfp);
@@ -1431,30 +1495,24 @@ intel_engine_coredump_add_vma(struct intel_engine_coredump *ee,
 
 	while (capture) {
 		struct intel_engine_capture_vma *this = capture;
-		struct i915_vma *vma = this->vma;
+		struct i915_vma_snapshot *vsnap = this->vsnap;
 
 		add_vma(ee,
 			i915_vma_coredump_create(engine->gt,
-						 vma, this->name,
-						 compress));
+						 vsnap, compress));
 
-		i915_active_release(&vma->active);
+		i915_vma_snapshot_resource_unpin(vsnap, this->lockdep_cookie);
+		i915_vma_snapshot_put(vsnap);
 
 		capture = this->next;
 		kfree(this);
 	}
 
-	add_vma(ee,
-		i915_vma_coredump_create(engine->gt,
-					 engine->status_page.vma,
-					 "HW Status",
-					 compress));
+	add_vma_coredump(ee, engine->gt, engine->status_page.vma,
+			 "HW Status", compress);
 
-	add_vma(ee,
-		i915_vma_coredump_create(engine->gt,
-					 engine->wa_ctx.vma,
-					 "WA context",
-					 compress));
+	add_vma_coredump(ee, engine->gt, engine->wa_ctx.vma,
+			 "WA context", compress);
 }
 
 static struct intel_engine_coredump *
@@ -1490,17 +1548,25 @@ capture_engine(struct intel_engine_cs *engine,
 		}
 	}
 	if (rq)
-		capture = intel_engine_coredump_add_request(ee, rq,
-							    ATOMIC_MAYFAIL);
+		rq = i915_request_get_rcu(rq);
+
+	if (!rq)
+		goto no_request_capture;
+
+	capture = intel_engine_coredump_add_request(ee, rq, ATOMIC_MAYFAIL);
 	if (!capture) {
-no_request_capture:
-		kfree(ee);
-		return NULL;
+		i915_request_put(rq);
+		goto no_request_capture;
 	}
 
 	intel_engine_coredump_add_vma(ee, capture, compress);
+	i915_request_put(rq);
 
 	return ee;
+
+no_request_capture:
+	kfree(ee);
+	return NULL;
 }
 
 static void
@@ -1554,10 +1620,8 @@ gt_record_uc(struct intel_gt_coredump *gt,
 	 */
 	error_uc->guc_fw.path = kstrdup(uc->guc.fw.path, ALLOW_FAIL);
 	error_uc->huc_fw.path = kstrdup(uc->huc.fw.path, ALLOW_FAIL);
-	error_uc->guc_log =
-		i915_vma_coredump_create(gt->_gt,
-					 uc->guc.log.vma, "GuC log buffer",
-					 compress);
+	error_uc->guc_log = create_vma_coredump(gt->_gt, uc->guc.log.vma,
+						"GuC log buffer", compress);
 
 	return error_uc;
 }
@@ -1843,8 +1907,8 @@ void i915_vma_capture_finish(struct intel_gt_coredump *gt,
 	kfree(compress);
 }
 
-struct i915_gpu_coredump *
-i915_gpu_coredump(struct intel_gt *gt, intel_engine_mask_t engine_mask)
+static struct i915_gpu_coredump *
+__i915_gpu_coredump(struct intel_gt *gt, intel_engine_mask_t engine_mask)
 {
 	struct drm_i915_private *i915 = gt->i915;
 	struct i915_gpu_coredump *error;
@@ -1885,6 +1949,22 @@ i915_gpu_coredump(struct intel_gt *gt, intel_engine_mask_t engine_mask)
 	return error;
 }
 
+struct i915_gpu_coredump *
+i915_gpu_coredump(struct intel_gt *gt, intel_engine_mask_t engine_mask)
+{
+	static DEFINE_MUTEX(capture_mutex);
+	int ret = mutex_lock_interruptible(&capture_mutex);
+	struct i915_gpu_coredump *dump;
+
+	if (ret)
+		return ERR_PTR(ret);
+
+	dump = __i915_gpu_coredump(gt, engine_mask);
+	mutex_unlock(&capture_mutex);
+
+	return dump;
+}
+
 void i915_error_state_store(struct i915_gpu_coredump *error)
 {
 	struct drm_i915_private *i915;
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index 623273aca09e..ee855dc86972 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -113,6 +113,10 @@ static void i915_fence_release(struct dma_fence *fence)
 	GEM_BUG_ON(rq->guc_prio != GUC_PRIO_INIT &&
 		   rq->guc_prio != GUC_PRIO_FINI);
 
+	i915_request_free_capture_list(fetch_and_zero(&rq->capture_list));
+	if (i915_vma_snapshot_present(&rq->batch_snapshot))
+		i915_vma_snapshot_put_onstack(&rq->batch_snapshot);
+
 	/*
 	 * The request is put onto a RCU freelist (i.e. the address
 	 * is immediately reused), mark the fences as being freed now.
@@ -186,19 +190,6 @@ void i915_request_notify_execute_cb_imm(struct i915_request *rq)
 	__notify_execute_cb(rq, irq_work_imm);
 }
 
-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;
@@ -303,6 +294,37 @@ static void __rq_cancel_watchdog(struct i915_request *rq)
 		i915_request_put(rq);
 }
 
+#if IS_ENABLED(CONFIG_DRM_I915_CAPTURE_ERROR)
+
+/**
+ * i915_request_free_capture_list - Free a capture list
+ * @capture: Pointer to the first list item or NULL
+ *
+ */
+void i915_request_free_capture_list(struct i915_capture_list *capture)
+{
+	while (capture) {
+		struct i915_capture_list *next = capture->next;
+
+		i915_vma_snapshot_put(capture->vma_snapshot);
+		capture = next;
+	}
+}
+
+#define assert_capture_list_is_null(_rq) GEM_BUG_ON((_rq)->capture_list)
+
+#define clear_capture_list(_rq) ((_rq)->capture_list = NULL)
+
+#else
+
+#define i915_request_free_capture_list(_a) do {} while (0)
+
+#define assert_capture_list_is_null(_a) do {} while (0)
+
+#define clear_capture_list(_rq) do {} while (0)
+
+#endif
+
 bool i915_request_retire(struct i915_request *rq)
 {
 	if (!__i915_request_is_complete(rq))
@@ -359,7 +381,6 @@ bool i915_request_retire(struct i915_request *rq)
 	intel_context_exit(rq->context);
 	intel_context_unpin(rq->context);
 
-	free_capture_list(rq);
 	i915_sched_node_fini(&rq->sched);
 	i915_request_put(rq);
 
@@ -829,11 +850,18 @@ static void __i915_request_ctor(void *arg)
 	i915_sw_fence_init(&rq->submit, submit_notify);
 	i915_sw_fence_init(&rq->semaphore, semaphore_notify);
 
-	rq->capture_list = NULL;
+	clear_capture_list(rq);
+	rq->batch_snapshot.present = false;
 
 	init_llist_head(&rq->execute_cb);
 }
 
+#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
+#define clear_batch_ptr(_rq) ((_rq)->batch = NULL)
+#else
+#define clear_batch_ptr(_a) do {} while (0)
+#endif
+
 struct i915_request *
 __i915_request_create(struct intel_context *ce, gfp_t gfp)
 {
@@ -925,10 +953,11 @@ __i915_request_create(struct intel_context *ce, gfp_t gfp)
 	i915_sched_node_reinit(&rq->sched);
 
 	/* No zalloc, everything must be cleared after use */
-	rq->batch = NULL;
+	clear_batch_ptr(rq);
 	__rq_init_watchdog(rq);
-	GEM_BUG_ON(rq->capture_list);
+	assert_capture_list_is_null(rq);
 	GEM_BUG_ON(!llist_empty(&rq->execute_cb));
+	GEM_BUG_ON(i915_vma_snapshot_present(&rq->batch_snapshot));
 
 	/*
 	 * Reserve space in the ring buffer for all the commands required to
diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
index dc359242d1ae..16aba0cb32d6 100644
--- a/drivers/gpu/drm/i915/i915_request.h
+++ b/drivers/gpu/drm/i915/i915_request.h
@@ -40,6 +40,7 @@
 #include "i915_scheduler.h"
 #include "i915_selftest.h"
 #include "i915_sw_fence.h"
+#include "i915_vma_snapshot.h"
 
 #include <uapi/drm/i915_drm.h>
 
@@ -48,11 +49,17 @@ struct drm_i915_gem_object;
 struct drm_printer;
 struct i915_request;
 
+#if IS_ENABLED(CONFIG_DRM_I915_CAPTURE_ERROR)
 struct i915_capture_list {
+	struct i915_vma_snapshot *vma_snapshot;
 	struct i915_capture_list *next;
-	struct i915_vma *vma;
 };
 
+void i915_request_free_capture_list(struct i915_capture_list *capture);
+#else
+#define i915_request_free_capture_list(_a) do {} while (0)
+#endif
+
 #define RQ_TRACE(rq, fmt, ...) do {					\
 	const struct i915_request *rq__ = (rq);				\
 	ENGINE_TRACE(rq__->engine, "fence %llx:%lld, current %d " fmt,	\
@@ -289,10 +296,12 @@ struct i915_request {
 	/** Preallocate space in the ring for the emitting the request */
 	u32 reserved_space;
 
-	/** Batch buffer related to this request if any (used for
-	 * error state dump only).
-	 */
-	struct i915_vma *batch;
+	/** Batch buffer pointer for selftest internal use. */
+	I915_SELFTEST_DECLARE(struct i915_vma *batch);
+
+	struct i915_vma_snapshot batch_snapshot;
+
+#if IS_ENABLED(CONFIG_DRM_I915_CAPTURE_ERROR)
 	/**
 	 * Additional buffers requested by userspace to be captured upon
 	 * a GPU hang. The vma/obj on this list are protected by their
@@ -300,6 +309,7 @@ struct i915_request {
 	 * on the active_list (of their final request).
 	 */
 	struct i915_capture_list *capture_list;
+#endif
 
 	/** Time at which this request was emitted, in jiffies. */
 	unsigned long emitted_jiffies;
diff --git a/drivers/gpu/drm/i915/i915_vma_snapshot.c b/drivers/gpu/drm/i915/i915_vma_snapshot.c
new file mode 100644
index 000000000000..44985d600f96
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_vma_snapshot.c
@@ -0,0 +1,137 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2021 Intel Corporation
+ */
+
+#include "i915_vma_snapshot.h"
+#include "i915_vma_types.h"
+#include "i915_vma.h"
+
+/**
+ * i915_vma_snapshot_init - Initialize a struct i915_vma_snapshot from
+ * a struct i915_vma.
+ * @vsnap: The i915_vma_snapshot to init.
+ * @vma: A struct i915_vma used to initialize @vsnap.
+ * @name: Name associated with the snapshot. The character pointer needs to
+ * stay alive over the lifitime of the shapsot
+ */
+void i915_vma_snapshot_init(struct i915_vma_snapshot *vsnap,
+			    struct i915_vma *vma,
+			    const char *name)
+{
+	if (!i915_vma_is_pinned(vma))
+		assert_object_held(vma->obj);
+
+	vsnap->name = name;
+	vsnap->size = vma->size;
+	vsnap->obj_size = vma->obj->base.size;
+	vsnap->gtt_offset = vma->node.start;
+	vsnap->gtt_size = vma->node.size;
+	vsnap->page_sizes = vma->page_sizes.gtt;
+	vsnap->pages = vma->pages;
+	vsnap->pages_rsgt = NULL;
+	vsnap->mr = NULL;
+	if (vma->obj->mm.rsgt)
+		vsnap->pages_rsgt = i915_refct_sgt_get(vma->obj->mm.rsgt);
+	if (vma->obj->mm.region)
+		vsnap->mr = intel_memory_region_get(vma->obj->mm.region);
+	kref_init(&vsnap->kref);
+	vsnap->vma_resource = &vma->active;
+	vsnap->onstack = false;
+	vsnap->present = true;
+}
+
+/**
+ * i915_vma_snapshot_init_onstack - Initialize a struct i915_vma_snapshot from
+ * a struct i915_vma, but avoid kfreeing it on last put.
+ * @vsnap: The i915_vma_snapshot to init.
+ * @vma: A struct i915_vma used to initialize @vsnap.
+ * @name: Name associated with the snapshot. The character pointer needs to
+ * stay alive over the lifitime of the shapsot
+ */
+void i915_vma_snapshot_init_onstack(struct i915_vma_snapshot *vsnap,
+				    struct i915_vma *vma,
+				    const char *name)
+{
+	i915_vma_snapshot_init(vsnap, vma, name);
+	vsnap->onstack = true;
+}
+
+static void vma_snapshot_release(struct kref *ref)
+{
+	struct i915_vma_snapshot *vsnap =
+		container_of(ref, typeof(*vsnap), kref);
+
+	vsnap->present = false;
+	if (vsnap->mr)
+		intel_memory_region_put(vsnap->mr);
+	if (vsnap->pages_rsgt)
+		i915_refct_sgt_put(vsnap->pages_rsgt);
+	if (!vsnap->onstack)
+		kfree(vsnap);
+}
+
+/**
+ * i915_vma_snapshot_put - Put an i915_vma_snapshot pointer reference
+ * @vsnap: The pointer reference
+ */
+void i915_vma_snapshot_put(struct i915_vma_snapshot *vsnap)
+{
+	kref_put(&vsnap->kref, vma_snapshot_release);
+}
+
+/**
+ * i915_vma_snapshot_put_onstack - Put an onstcak i915_vma_snapshot pointer
+ * reference and varify that the structure is released
+ * @vsnap: The pointer reference
+ *
+ * This function is intended to be paired with a i915_vma_init_onstack()
+ * and should be called before exiting the scope that declared or
+ * freeing the structure that embedded @vsnap to verify that all references
+ * have been released.
+ */
+void i915_vma_snapshot_put_onstack(struct i915_vma_snapshot *vsnap)
+{
+	if (!kref_put(&vsnap->kref, vma_snapshot_release))
+		GEM_BUG_ON(1);
+}
+
+/**
+ * i915_vma_snapshot_resource_pin - Temporarily block the memory the
+ * vma snapshot is pointing to from being released.
+ * @vsnap: The vma snapshot.
+ * @lockdep_cookie: Pointer to bool needed for lockdep support. This needs
+ * to be passed to the paired i915_vma_snapshot_resource_unpin.
+ *
+ * This function will temporarily try to hold up a fence or similar structure
+ * and will therefore enter a fence signaling critical section.
+ *
+ * Return: true if we succeeded in blocking the memory from being released,
+ * false otherwise.
+ */
+bool i915_vma_snapshot_resource_pin(struct i915_vma_snapshot *vsnap,
+				    bool *lockdep_cookie)
+{
+	bool pinned = i915_active_acquire_if_busy(vsnap->vma_resource);
+
+	if (pinned)
+		*lockdep_cookie = dma_fence_begin_signalling();
+
+	return pinned;
+}
+
+/**
+ * i915_vma_snapshot_resource_unpin - Unblock vma snapshot memory from
+ * being released.
+ * @vsnap: The vma snapshot.
+ * @lockdep_cookie: Cookie returned from matching i915_vma_resource_pin().
+ *
+ * Might leave a fence signalling critical section and signal a fence.
+ */
+void i915_vma_snapshot_resource_unpin(struct i915_vma_snapshot *vsnap,
+				      bool lockdep_cookie)
+{
+	dma_fence_end_signalling(lockdep_cookie);
+
+	return i915_active_release(vsnap->vma_resource);
+}
diff --git a/drivers/gpu/drm/i915/i915_vma_snapshot.h b/drivers/gpu/drm/i915/i915_vma_snapshot.h
new file mode 100644
index 000000000000..940581df4622
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_vma_snapshot.h
@@ -0,0 +1,112 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2021 Intel Corporation
+ */
+#ifndef _I915_VMA_SNAPSHOT_H_
+#define _I915_VMA_SNAPSHOT_H_
+
+#include <linux/kref.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+struct i915_active;
+struct i915_refct_sgt;
+struct i915_vma;
+struct intel_memory_region;
+struct sg_table;
+
+/**
+ * DOC: Simple utilities for snapshotting GPU vma metadata, later used for
+ * error capture. Vi use a separate header for this to avoid issues due to
+ * recursive header includes.
+ */
+
+/**
+ * struct i915_vma_snapshot - Snapshot of vma metadata.
+ * @size: The vma size in bytes.
+ * @obj_size: The size of the underlying object in bytes.
+ * @gtt_offset: The gtt offset the vma is bound to.
+ * @gtt_size: The size in bytes allocated for the vma in the GTT.
+ * @pages: The struct sg_table pointing to the pages bound.
+ * @pages_rsgt: The refcounted sg_table holding the reference for @pages if any.
+ * @mr: The memory region pointed for the pages bound.
+ * @kref: Reference for this structure.
+ * @vma_resource: FIXME: A means to keep the unbind fence from signaling.
+ * Temporarily while we have only sync unbinds, and still use the vma
+ * active, we use that. With async unbinding we need a signaling refcount
+ * for the unbind fence.
+ * @page_sizes: The vma GTT page sizes information.
+ * @onstack: Whether the structure shouldn't be freed on final put.
+ * @present: Whether the structure is present and initialized.
+ */
+struct i915_vma_snapshot {
+	const char *name;
+	size_t size;
+	size_t obj_size;
+	size_t gtt_offset;
+	size_t gtt_size;
+	struct sg_table *pages;
+	struct i915_refct_sgt *pages_rsgt;
+	struct intel_memory_region *mr;
+	struct kref kref;
+	struct i915_active *vma_resource;
+	u32 page_sizes;
+	bool onstack:1;
+	bool present:1;
+};
+
+void i915_vma_snapshot_init(struct i915_vma_snapshot *vsnap,
+			    struct i915_vma *vma,
+			    const char *name);
+
+void i915_vma_snapshot_init_onstack(struct i915_vma_snapshot *vsnap,
+				    struct i915_vma *vma,
+				    const char *name);
+
+void i915_vma_snapshot_put(struct i915_vma_snapshot *vsnap);
+
+void i915_vma_snapshot_put_onstack(struct i915_vma_snapshot *vsnap);
+
+bool i915_vma_snapshot_resource_pin(struct i915_vma_snapshot *vsnap,
+				    bool *lockdep_cookie);
+
+void i915_vma_snapshot_resource_unpin(struct i915_vma_snapshot *vsnap,
+				      bool lockdep_cookie);
+
+/**
+ * i915_vma_snapshot_alloc - Allocate a struct i915_vma_snapshot
+ * @gfp: Allocation mode.
+ *
+ * Return: A pointer to a struct i915_vma_snapshot if successful.
+ * NULL otherwise.
+ */
+static inline struct i915_vma_snapshot *i915_vma_snapshot_alloc(gfp_t gfp)
+{
+	return kmalloc(sizeof(struct i915_vma_snapshot), gfp);
+}
+
+/**
+ * i915_vma_snapshot_get - Take a reference on a struct i915_vma_snapshot
+ *
+ * Return: A pointer to a struct i915_vma_snapshot.
+ */
+static inline struct i915_vma_snapshot *
+i915_vma_snapshot_get(struct i915_vma_snapshot *vsnap)
+{
+	kref_get(&vsnap->kref);
+	return vsnap;
+}
+
+/**
+ * i915_vma_snapshot_present - Whether a struct i915_vma_snapshot is
+ * present and initialized.
+ *
+ * Return: true if present and initialized; false otherwise.
+ */
+static inline bool
+i915_vma_snapshot_present(const struct i915_vma_snapshot *vsnap)
+{
+	return vsnap && vsnap->present;
+}
+
+#endif
-- 
2.31.1



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