Re: [PATCH v3 3/6] drm/i915 Implement LMEM backup and restore for suspend / resume

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On 14/09/2021 20:31, Thomas Hellström wrote:
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.

Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
---
  drivers/gpu/drm/i915/Makefile                 |   1 +
  .../gpu/drm/i915/gem/i915_gem_object_types.h  |   1 +
  drivers/gpu/drm/i915/gem/i915_gem_pm.c        |  92 +++++++-
  drivers/gpu/drm/i915/gem/i915_gem_pm.h        |   3 +-
  drivers/gpu/drm/i915/gem/i915_gem_ttm.c       |  29 ++-
  drivers/gpu/drm/i915/gem/i915_gem_ttm.h       |  10 +
  drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c    | 203 ++++++++++++++++++
  drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.h    |  24 +++
  drivers/gpu/drm/i915/gt/intel_gt_pm.c         |   4 +-
  drivers/gpu/drm/i915/i915_drv.c               |  10 +-
  drivers/gpu/drm/i915/i915_drv.h               |   2 +-
  11 files changed, 362 insertions(+), 17 deletions(-)
  create mode 100644 drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c
  create mode 100644 drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.h

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 9d371be7dc5c..f9b69492a56c 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/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
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
index 2471f36aaff3..734cc8e16481 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
+++ b/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;
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pm.c b/drivers/gpu/drm/i915/gem/i915_gem_pm.c
index 8b9d7d14c4bd..8736ae1dfbb2 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_pm.c
+++ b/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"
@@ -39,7 +40,86 @@ void i915_gem_suspend(struct drm_i915_private *i915)
  	i915_gem_drain_freed_objects(i915);
  }
-void i915_gem_suspend_late(struct drm_i915_private *i915)
+static int lmem_restore(struct drm_i915_private *i915, bool allow_gpu)
+{
+	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, allow_gpu);
+			if (ret)
+				break;
+		}
+	}
+
+	return ret;
+}
+
+static int lmem_suspend(struct drm_i915_private *i915, bool allow_gpu,
+			bool backup_pinned)
+{
+	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, allow_gpu, backup_pinned);
+			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, true, false);
+	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, true, false);
+	if (ret)
+		goto out_recover;
+
+	/*
+	 * Remaining objects are backed up using memcpy once we've stopped
+	 * using the migrate context.
+	 */
+	ret = lmem_suspend(i915, false, true);
+	if (ret)
+		goto out_recover;
+
+	return 0;
+
+out_recover:
+	lmem_recover(i915);
+
+	return ret;
+}
+
+int i915_gem_suspend_late(struct drm_i915_private *i915)
  {
  	struct drm_i915_gem_object *obj;
  	struct list_head *phases[] = {
@@ -83,6 +163,8 @@ void i915_gem_suspend_late(struct drm_i915_private *i915)
  	spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
  	if (flush)
  		wbinvd_on_all_cpus();
+
+	return 0;


We can drop this change now?

I guess only slight concern is all the GEM_WARN_ON() instead of proper error handling in some places, but hopefully these should never be hit in practice,
Reviewed-by: Matthew Auld <matthew.auld@xxxxxxxxx>



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