drm/i915 Implement LMEM backup and restore for suspend / resume

Just evict unpinned objects to system. For pinned LMEM objects,
make a backup system object and blit the contents to that.

Backup is performed in three steps,
1: Opportunistically evict evictable objects using the gpu blitter.
2: After gt idle, evict evictable objects using the gpu blitter. This will
be modified in an upcoming patch to backup pinned objects that are not used
by the blitter itself.
3: Backup remaining pinned objects using memcpy.

Also move uC suspend to after 2) to make sure we have a functional GuC
during 2) if using GuC submission.

v2:
- Major refactor to make sure gem_exec_suspend@hang-SX subtests work, and
  suspend / resume works with a slightly modified GuC submission enabling
  patch series.

v3:
- Fix a potential use-after-free (Matthew Auld)
- Use i915_gem_object_create_shmem() instead of
  i915_gem_object_create_region (Matthew Auld)
- Minor simplifications (Matthew Auld)
- Fix up kerneldoc for i195_ttm_restore_region().
- Final lmem_suspend() call moved to i915_gem_backup_suspend from
  i915_gem_suspend_late, since the latter gets called at driver unload
  and we don't unnecessarily want to run it at that time.

v4:
- Interface change of ttm- & lmem suspend / resume functions to use
  flags rather than bools. (Matthew Auld)
- Completely drop the i915_gem_backup_suspend change (Matthew Auld)
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210922062527.865433-5-thomas.hellstrom@linux.intel.com

drivers/gpu/drm/i915/Makefile

@@ -154,6 +154,7 @@ gem-y += \
 	gem/i915_gem_throttle.o \
 	gem/i915_gem_tiling.o \
 	gem/i915_gem_ttm.o \
+	gem/i915_gem_ttm_pm.o \
 	gem/i915_gem_userptr.o \
 	gem/i915_gem_wait.o \
 	gem/i915_gemfs.o

drivers/gpu/drm/i915/gem/i915_gem_object_types.h

@@ -534,6 +534,7 @@ struct drm_i915_gem_object {
 	struct {
 		struct sg_table *cached_io_st;
 		struct i915_gem_object_page_iter get_io_page;
+		struct drm_i915_gem_object *backup;
 		bool created:1;
 	} ttm;
 

drivers/gpu/drm/i915/gem/i915_gem_pm.c

@@ -5,6 +5,7 @@
  */
 
 #include "gem/i915_gem_pm.h"
+#include "gem/i915_gem_ttm_pm.h"
 #include "gt/intel_gt.h"
 #include "gt/intel_gt_pm.h"
 #include "gt/intel_gt_requests.h"
@@ -39,6 +40,84 @@ void i915_gem_suspend(struct drm_i915_private *i915)
 	i915_gem_drain_freed_objects(i915);
 }
 
+static int lmem_restore(struct drm_i915_private *i915, u32 flags)
+{
+	struct intel_memory_region *mr;
+	int ret = 0, id;
+
+	for_each_memory_region(mr, i915, id) {
+		if (mr->type == INTEL_MEMORY_LOCAL) {
+			ret = i915_ttm_restore_region(mr, flags);
+			if (ret)
+				break;
+		}
+	}
+
+	return ret;
+}
+
+static int lmem_suspend(struct drm_i915_private *i915, u32 flags)
+{
+	struct intel_memory_region *mr;
+	int ret = 0, id;
+
+	for_each_memory_region(mr, i915, id) {
+		if (mr->type == INTEL_MEMORY_LOCAL) {
+			ret = i915_ttm_backup_region(mr, flags);
+			if (ret)
+				break;
+		}
+	}
+
+	return ret;
+}
+
+static void lmem_recover(struct drm_i915_private *i915)
+{
+	struct intel_memory_region *mr;
+	int id;
+
+	for_each_memory_region(mr, i915, id)
+		if (mr->type == INTEL_MEMORY_LOCAL)
+			i915_ttm_recover_region(mr);
+}
+
+int i915_gem_backup_suspend(struct drm_i915_private *i915)
+{
+	int ret;
+
+	/* Opportunistically try to evict unpinned objects */
+	ret = lmem_suspend(i915, I915_TTM_BACKUP_ALLOW_GPU);
+	if (ret)
+		goto out_recover;
+
+	i915_gem_suspend(i915);
+
+	/*
+	 * More objects may have become unpinned as requests were
+	 * retired. Now try to evict again. The gt may be wedged here
+	 * in which case we automatically fall back to memcpy.
+	 */
+	ret = lmem_suspend(i915, I915_TTM_BACKUP_ALLOW_GPU);
+	if (ret)
+		goto out_recover;
+
+	/*
+	 * Remaining objects are backed up using memcpy once we've stopped
+	 * using the migrate context.
+	 */
+	ret = lmem_suspend(i915, I915_TTM_BACKUP_PINNED);
+	if (ret)
+		goto out_recover;
+
+	return 0;
+
+out_recover:
+	lmem_recover(i915);
+
+	return ret;
+}
+
 void i915_gem_suspend_late(struct drm_i915_private *i915)
 {
 	struct drm_i915_gem_object *obj;
@@ -128,12 +207,20 @@ int i915_gem_freeze_late(struct drm_i915_private *i915)
 
 void i915_gem_resume(struct drm_i915_private *i915)
 {
+	int ret;
+
 	GEM_TRACE("%s\n", dev_name(i915->drm.dev));
 
+	ret = lmem_restore(i915, 0);
+	GEM_WARN_ON(ret);
+
 	/*
 	 * As we didn't flush the kernel context before suspend, we cannot
 	 * guarantee that the context image is complete. So let's just reset
 	 * it and start again.
 	 */
 	intel_gt_resume(&i915->gt);
+
+	ret = lmem_restore(i915, I915_TTM_BACKUP_ALLOW_GPU);
+	GEM_WARN_ON(ret);
 }

drivers/gpu/drm/i915/gem/i915_gem_pm.h

@@ -18,6 +18,7 @@ void i915_gem_idle_work_handler(struct work_struct *work);
 
 void i915_gem_suspend(struct drm_i915_private *i915);
 void i915_gem_suspend_late(struct drm_i915_private *i915);
+int i915_gem_backup_suspend(struct drm_i915_private *i915);
 
 int i915_gem_freeze(struct drm_i915_private *i915);
 int i915_gem_freeze_late(struct drm_i915_private *i915);

drivers/gpu/drm/i915/gem/i915_gem_ttm.c

@@ -10,18 +10,16 @@
 #include "intel_memory_region.h"
 #include "intel_region_ttm.h"
 
+#include "gem/i915_gem_mman.h"
 #include "gem/i915_gem_object.h"
 #include "gem/i915_gem_region.h"
 #include "gem/i915_gem_ttm.h"
-#include "gem/i915_gem_mman.h"
+#include "gem/i915_gem_ttm_pm.h"
 
-#include "gt/intel_migrate.h"
-#include "gt/intel_engine_pm.h"
 
-#define I915_PL_LMEM0 TTM_PL_PRIV
-#define I915_PL_SYSTEM TTM_PL_SYSTEM
-#define I915_PL_STOLEN TTM_PL_VRAM
-#define I915_PL_GGTT TTM_PL_TT
+#include "gt/intel_engine_pm.h"
+#include "gt/intel_gt.h"
+#include "gt/intel_migrate.h"
 
 #define I915_TTM_PRIO_PURGE     0
 #define I915_TTM_PRIO_NO_PAGES  1
@@ -64,6 +62,20 @@ static struct ttm_placement i915_sys_placement = {
 	.busy_placement = &sys_placement_flags,
 };
 
+/**
+ * i915_ttm_sys_placement - Return the struct ttm_placement to be
+ * used for an object in system memory.
+ *
+ * Rather than making the struct extern, use this
+ * function.
+ *
+ * Return: A pointer to a static variable for sys placement.
+ */
+struct ttm_placement *i915_ttm_sys_placement(void)
+{
+	return &i915_sys_placement;
+}
+
 static int i915_ttm_err_to_gem(int err)
 {
 	/* Fastpath */
@@ -443,7 +455,7 @@ static int i915_ttm_accel_move(struct ttm_buffer_object *bo,
 	enum i915_cache_level src_level, dst_level;
 	int ret;
 
-	if (!i915->gt.migrate.context)
+	if (!i915->gt.migrate.context || intel_gt_is_wedged(&i915->gt))
 		return -EINVAL;
 
 	dst_level = i915_ttm_cache_level(i915, dst_mem, dst_ttm);
@@ -887,6 +899,8 @@ void i915_ttm_bo_destroy(struct ttm_buffer_object *bo)
 {
 	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
 
+	i915_ttm_backup_free(obj);
+
 	/* This releases all gem object bindings to the backend. */
 	__i915_gem_free_object(obj);
 

drivers/gpu/drm/i915/gem/i915_gem_ttm.h

@@ -50,4 +50,14 @@ int __i915_gem_ttm_object_init(struct intel_memory_region *mem,
 int i915_gem_obj_copy_ttm(struct drm_i915_gem_object *dst,
 			  struct drm_i915_gem_object *src,
 			  bool allow_accel, bool intr);
+
+/* Internal I915 TTM declarations and definitions below. */
+
+#define I915_PL_LMEM0 TTM_PL_PRIV
+#define I915_PL_SYSTEM TTM_PL_SYSTEM
+#define I915_PL_STOLEN TTM_PL_VRAM
+#define I915_PL_GGTT TTM_PL_TT
+
+struct ttm_placement *i915_ttm_sys_placement(void);
+
 #endif

drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c

+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2021 Intel Corporation
+ */
+
+#include <drm/ttm/ttm_placement.h>
+#include <drm/ttm/ttm_tt.h>
+
+#include "i915_drv.h"
+#include "intel_memory_region.h"
+#include "intel_region_ttm.h"
+
+#include "gem/i915_gem_region.h"
+#include "gem/i915_gem_ttm.h"
+#include "gem/i915_gem_ttm_pm.h"
+
+/**
+ * i915_ttm_backup_free - Free any backup attached to this object
+ * @obj: The object whose backup is to be freed.
+ */
+void i915_ttm_backup_free(struct drm_i915_gem_object *obj)
+{
+	if (obj->ttm.backup) {
+		i915_gem_object_put(obj->ttm.backup);
+		obj->ttm.backup = NULL;
+	}
+}
+
+/**
+ * struct i915_gem_ttm_pm_apply - Apply-to-region subclass for restore
+ * @base: The i915_gem_apply_to_region we derive from.
+ * @allow_gpu: Whether using the gpu blitter is allowed.
+ * @backup_pinned: On backup, backup also pinned objects.
+ */
+struct i915_gem_ttm_pm_apply {
+	struct i915_gem_apply_to_region base;
+	bool allow_gpu : 1;
+	bool backup_pinned : 1;
+};
+
+static int i915_ttm_backup(struct i915_gem_apply_to_region *apply,
+			   struct drm_i915_gem_object *obj)
+{
+	struct i915_gem_ttm_pm_apply *pm_apply =
+		container_of(apply, typeof(*pm_apply), base);
+	struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
+	struct ttm_buffer_object *backup_bo;
+	struct drm_i915_private *i915 =
+		container_of(bo->bdev, typeof(*i915), bdev);
+	struct drm_i915_gem_object *backup;
+	struct ttm_operation_ctx ctx = {};
+	int err = 0;
+
+	if (bo->resource->mem_type == I915_PL_SYSTEM || obj->ttm.backup)
+		return 0;
+
+	if (pm_apply->allow_gpu && i915_gem_object_evictable(obj))
+		return ttm_bo_validate(bo, i915_ttm_sys_placement(), &ctx);
+
+	if (!pm_apply->backup_pinned)
+		return 0;
+
+	backup = i915_gem_object_create_shmem(i915, obj->base.size);
+	if (IS_ERR(backup))
+		return PTR_ERR(backup);
+
+	err = i915_gem_object_lock(backup, apply->ww);
+	if (err)
+		goto out_no_lock;
+
+	backup_bo = i915_gem_to_ttm(backup);
+	err = ttm_tt_populate(backup_bo->bdev, backup_bo->ttm, &ctx);
+	if (err)
+		goto out_no_populate;
+
+	err = i915_gem_obj_copy_ttm(backup, obj, pm_apply->allow_gpu, false);
+	GEM_WARN_ON(err);
+
+	obj->ttm.backup = backup;
+	return 0;
+
+out_no_populate:
+	i915_gem_ww_unlock_single(backup);
+out_no_lock:
+	i915_gem_object_put(backup);
+
+	return err;
+}
+
+static int i915_ttm_recover(struct i915_gem_apply_to_region *apply,
+			    struct drm_i915_gem_object *obj)
+{
+	i915_ttm_backup_free(obj);
+	return 0;
+}
+
+/**
+ * i915_ttm_recover_region - Free the backup of all objects of a region
+ * @mr: The memory region
+ *
+ * Checks all objects of a region if there is backup attached and if so
+ * frees that backup. Typically this is called to recover after a partially
+ * performed backup.
+ */
+void i915_ttm_recover_region(struct intel_memory_region *mr)
+{
+	static const struct i915_gem_apply_to_region_ops recover_ops = {
+		.process_obj = i915_ttm_recover,
+	};
+	struct i915_gem_apply_to_region apply = {.ops = &recover_ops};
+	int ret;
+
+	ret = i915_gem_process_region(mr, &apply);
+	GEM_WARN_ON(ret);
+}
+
+/**
+ * i915_ttm_backup_region - Back up all objects of a region to smem.
+ * @mr: The memory region
+ * @allow_gpu: Whether to allow the gpu blitter for this backup.
+ * @backup_pinned: Backup also pinned objects.
+ *
+ * Loops over all objects of a region and either evicts them if they are
+ * evictable or backs them up using a backup object if they are pinned.
+ *
+ * Return: Zero on success. Negative error code on error.
+ */
+int i915_ttm_backup_region(struct intel_memory_region *mr, u32 flags)
+{
+	static const struct i915_gem_apply_to_region_ops backup_ops = {
+		.process_obj = i915_ttm_backup,
+	};
+	struct i915_gem_ttm_pm_apply pm_apply = {
+		.base = {.ops = &backup_ops},
+		.allow_gpu = flags & I915_TTM_BACKUP_ALLOW_GPU,
+		.backup_pinned = flags & I915_TTM_BACKUP_PINNED,
+	};
+
+	return i915_gem_process_region(mr, &pm_apply.base);
+}
+
+static int i915_ttm_restore(struct i915_gem_apply_to_region *apply,
+			    struct drm_i915_gem_object *obj)
+{
+	struct i915_gem_ttm_pm_apply *pm_apply =
+		container_of(apply, typeof(*pm_apply), base);
+	struct drm_i915_gem_object *backup = obj->ttm.backup;
+	struct ttm_buffer_object *backup_bo = i915_gem_to_ttm(backup);
+	struct ttm_operation_ctx ctx = {};
+	int err;
+
+	if (!backup)
+		return 0;
+
+	if (!pm_apply->allow_gpu && (obj->flags & I915_BO_ALLOC_USER))
+		return 0;
+
+	err = i915_gem_object_lock(backup, apply->ww);
+	if (err)
+		return err;
+
+	/* Content may have been swapped. */
+	err = ttm_tt_populate(backup_bo->bdev, backup_bo->ttm, &ctx);
+	if (!err) {
+		err = i915_gem_obj_copy_ttm(obj, backup, pm_apply->allow_gpu,
+					    false);
+		GEM_WARN_ON(err);
+
+		obj->ttm.backup = NULL;
+		err = 0;
+	}
+
+	i915_gem_ww_unlock_single(backup);
+
+	if (!err)
+		i915_gem_object_put(backup);
+
+	return err;
+}
+
+/**
+ * i915_ttm_restore_region - Restore backed-up objects of a region from smem.
+ * @mr: The memory region
+ * @allow_gpu: Whether to allow the gpu blitter to recover.
+ *
+ * Loops over all objects of a region and if they are backed-up, restores
+ * them from smem.
+ *
+ * Return: Zero on success. Negative error code on error.
+ */
+int i915_ttm_restore_region(struct intel_memory_region *mr, u32 flags)
+{
+	static const struct i915_gem_apply_to_region_ops restore_ops = {
+		.process_obj = i915_ttm_restore,
+	};
+	struct i915_gem_ttm_pm_apply pm_apply = {
+		.base = {.ops = &restore_ops},
+		.allow_gpu = flags & I915_TTM_BACKUP_ALLOW_GPU,
+	};
+
+	return i915_gem_process_region(mr, &pm_apply.base);
+}

drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.h

+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2021 Intel Corporation
+ */
+
+#ifndef _I915_GEM_TTM_PM_H_
+#define _I915_GEM_TTM_PM_H_
+
+#include <linux/types.h>
+
+struct intel_memory_region;
+struct drm_i915_gem_object;
+
+#define I915_TTM_BACKUP_ALLOW_GPU BIT(0)
+#define I915_TTM_BACKUP_PINNED    BIT(1)
+
+int i915_ttm_backup_region(struct intel_memory_region *mr, u32 flags);
+
+void i915_ttm_recover_region(struct intel_memory_region *mr);
+
+int i915_ttm_restore_region(struct intel_memory_region *mr, u32 flags);
+
+/* Internal I915 TTM functions below. */
+void i915_ttm_backup_free(struct drm_i915_gem_object *obj);
+
+#endif

drivers/gpu/drm/i915/gt/intel_gt_pm.c

@@ -297,8 +297,6 @@ void intel_gt_suspend_prepare(struct intel_gt *gt)
 {
 	user_forcewake(gt, true);
 	wait_for_suspend(gt);
-
-	intel_uc_suspend(&gt->uc);
 }
 
 static suspend_state_t pm_suspend_target(void)
@@ -322,6 +320,8 @@ void intel_gt_suspend_late(struct intel_gt *gt)
 
 	GEM_BUG_ON(gt->awake);
 
+	intel_uc_suspend(&gt->uc);
+
 	/*
 	 * On disabling the device, we want to turn off HW access to memory
 	 * that we no longer own.

drivers/gpu/drm/i915/i915_drv.c

@@ -1094,9 +1094,7 @@ static int i915_drm_prepare(struct drm_device *dev)
 	 * split out that work and pull it forward so that after point,
 	 * the GPU is not woken again.
 	 */
-	i915_gem_suspend(i915);
-
-	return 0;
+	return i915_gem_backup_suspend(i915);
 }
 
 static int i915_drm_suspend(struct drm_device *dev)