Re: [PATCH v6 7/9] drm/i915: Reduce the number of objects subject to memcpy recover

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On 9/23/21 11:44 AM, Matthew Auld wrote:
On 22/09/2021 07:25, Thomas Hellström wrote:
We really only need memcpy restore for objects that affect the
operability of the migrate context. That is, primarily the page-table
objects of the migrate VM.

Add an object flag, I915_BO_ALLOC_PM_EARLY for objects that need early
restores using memcpy and a way to assign LMEM page-table object flags
to be used by the vms.

Restore objects without this flag with the gpu blitter and only objects
carrying the flag using TTM memcpy.

Initially mark the migrate, gt, gtt and vgpu vms to use this flag, and
defer for a later audit which vms actually need it. Most importantly, user-
allocated vms with pinned page-table objects can be restored using the
blitter.

Performance-wise memcpy restore is probably as fast as gpu restore if not
faster, but using gpu restore will help tackling future restrictions in
mappable LMEM size.

v4:
- Don't mark the aliasing ppgtt page table flags for early resume, but
   rather the ggtt page table flags as intended. (Matthew Auld)
- The check for user buffer objects during early resume is pointless, since
   they are never marked I915_BO_ALLOC_PM_EARLY. (Matthew Auld)
v5:
- Mark GuC LMEM objects with I915_BO_ALLOC_PM_EARLY to have them restored
   before we fire up the migrate context.

Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Reviewed-by: Matthew Auld <matthew.auld@xxxxxxxxx>
---
  drivers/gpu/drm/i915/gem/i915_gem_context.c      |  4 ++--
  drivers/gpu/drm/i915/gem/i915_gem_object_types.h |  9 ++++++---
  drivers/gpu/drm/i915/gem/i915_gem_pm.c           |  6 +++++-
  drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c       |  5 +++--
  drivers/gpu/drm/i915/gem/selftests/huge_pages.c  |  2 +-
  drivers/gpu/drm/i915/gt/gen6_ppgtt.c             |  2 +-
  drivers/gpu/drm/i915/gt/gen8_ppgtt.c             |  5 +++--
  drivers/gpu/drm/i915/gt/gen8_ppgtt.h             |  4 +++-
  drivers/gpu/drm/i915/gt/intel_ggtt.c             |  3 ++-
  drivers/gpu/drm/i915/gt/intel_gt.c               |  2 +-
  drivers/gpu/drm/i915/gt/intel_gtt.c              |  3 ++-
  drivers/gpu/drm/i915/gt/intel_gtt.h              |  9 +++++++--
  drivers/gpu/drm/i915/gt/intel_migrate.c          |  2 +-
  drivers/gpu/drm/i915/gt/intel_ppgtt.c            | 13 ++++++++-----
  drivers/gpu/drm/i915/gt/selftest_hangcheck.c     |  2 +-
  drivers/gpu/drm/i915/gt/uc/intel_guc.c           |  3 ++-
  drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c         |  7 +++++--
  drivers/gpu/drm/i915/gvt/scheduler.c             |  2 +-
  drivers/gpu/drm/i915/selftests/i915_gem_gtt.c    |  4 ++--
  19 files changed, 56 insertions(+), 31 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index c2ab0e22db0a..8208fd5b72c3 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -1287,7 +1287,7 @@ i915_gem_create_context(struct drm_i915_private *i915,
      } else if (HAS_FULL_PPGTT(i915)) {
          struct i915_ppgtt *ppgtt;
  -        ppgtt = i915_ppgtt_create(&i915->gt);
+        ppgtt = i915_ppgtt_create(&i915->gt, 0);
          if (IS_ERR(ppgtt)) {
              drm_dbg(&i915->drm, "PPGTT setup failed (%ld)\n",
                  PTR_ERR(ppgtt));
@@ -1465,7 +1465,7 @@ int i915_gem_vm_create_ioctl(struct drm_device *dev, void *data,
      if (args->flags)
          return -EINVAL;
  -    ppgtt = i915_ppgtt_create(&i915->gt);
+    ppgtt = i915_ppgtt_create(&i915->gt, 0);
      if (IS_ERR(ppgtt))
          return PTR_ERR(ppgtt);
  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 118691ce81d7..fa2ba9e2a4d0 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
@@ -294,13 +294,16 @@ struct drm_i915_gem_object {
  #define I915_BO_ALLOC_USER        BIT(3)
  /* Object is allowed to lose its contents on suspend / resume, even if pinned */
  #define I915_BO_ALLOC_PM_VOLATILE BIT(4)
+/* Object needs to be restored early using memcpy during resume */
+#define I915_BO_ALLOC_PM_EARLY    BIT(5)
  #define I915_BO_ALLOC_FLAGS (I915_BO_ALLOC_CONTIGUOUS | \
                   I915_BO_ALLOC_VOLATILE | \
                   I915_BO_ALLOC_CPU_CLEAR | \
                   I915_BO_ALLOC_USER | \
-                 I915_BO_ALLOC_PM_VOLATILE)
-#define I915_BO_READONLY          BIT(5)
-#define I915_TILING_QUIRK_BIT     6 /* unknown swizzling; do not release! */
+                 I915_BO_ALLOC_PM_VOLATILE | \
+                 I915_BO_ALLOC_PM_EARLY)
+#define I915_BO_READONLY          BIT(6)
+#define I915_TILING_QUIRK_BIT     7 /* unknown swizzling; do not release! */
        /**
       * @mem_flags - Mutable placement-related flags
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pm.c b/drivers/gpu/drm/i915/gem/i915_gem_pm.c
index 12b37b4c1192..726b40e1fbb0 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_pm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_pm.c
@@ -97,8 +97,12 @@ int i915_gem_backup_suspend(struct drm_i915_private *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.
+     * We allow also backing up pinned objects that have not been
+     * marked for early recover, and that may contain, for example,
+     * page-tables for the migrate context.
       */
-    ret = lmem_suspend(i915, I915_TTM_BACKUP_ALLOW_GPU);
+    ret = lmem_suspend(i915, I915_TTM_BACKUP_ALLOW_GPU |
+               I915_TTM_BACKUP_PINNED);
      if (ret)
          goto out_recover;
  diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c
index 03a00d193f40..3b6d14b5c604 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c
@@ -57,7 +57,8 @@ static int i915_ttm_backup(struct i915_gem_apply_to_region *apply,
      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)
+    if (!pm_apply->backup_pinned ||
+        (pm_apply->allow_gpu && (obj->flags & I915_BO_ALLOC_PM_EARLY)))
          return 0;
        if (obj->flags & I915_BO_ALLOC_PM_VOLATILE)
@@ -155,7 +156,7 @@ static int i915_ttm_restore(struct i915_gem_apply_to_region *apply,
      if (!backup)
          return 0;
  -    if (!pm_apply->allow_gpu && (obj->flags & I915_BO_ALLOC_USER))
+    if (!pm_apply->allow_gpu && !(obj->flags & I915_BO_ALLOC_PM_EARLY))
          return 0;
        err = i915_gem_object_lock(backup, apply->ww);
diff --git a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
index 0827634c842c..77d84a9e8789 100644
--- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
+++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
@@ -1645,7 +1645,7 @@ int i915_gem_huge_page_mock_selftests(void)
      mkwrite_device_info(dev_priv)->ppgtt_type = INTEL_PPGTT_FULL;
      mkwrite_device_info(dev_priv)->ppgtt_size = 48;
  -    ppgtt = i915_ppgtt_create(&dev_priv->gt);
+    ppgtt = i915_ppgtt_create(&dev_priv->gt, 0);
      if (IS_ERR(ppgtt)) {
          err = PTR_ERR(ppgtt);
          goto out_unlock;
diff --git a/drivers/gpu/drm/i915/gt/gen6_ppgtt.c b/drivers/gpu/drm/i915/gt/gen6_ppgtt.c
index 1aee5e6b1b23..890191f286e3 100644
--- a/drivers/gpu/drm/i915/gt/gen6_ppgtt.c
+++ b/drivers/gpu/drm/i915/gt/gen6_ppgtt.c
@@ -429,7 +429,7 @@ struct i915_ppgtt *gen6_ppgtt_create(struct intel_gt *gt)
      mutex_init(&ppgtt->flush);
      mutex_init(&ppgtt->pin_mutex);
  -    ppgtt_init(&ppgtt->base, gt);
+    ppgtt_init(&ppgtt->base, gt, 0);
      ppgtt->base.vm.pd_shift = ilog2(SZ_4K * SZ_4K / sizeof(gen6_pte_t));
      ppgtt->base.vm.top = 1;
  diff --git a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
index 6a5af995f5b1..037a9a6e4889 100644
--- a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
+++ b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
@@ -753,7 +753,8 @@ gen8_alloc_top_pd(struct i915_address_space *vm)
   * space.
   *
   */
-struct i915_ppgtt *gen8_ppgtt_create(struct intel_gt *gt)
+struct i915_ppgtt *gen8_ppgtt_create(struct intel_gt *gt,
+                     unsigned long lmem_pt_obj_flags)
  {
      struct i915_ppgtt *ppgtt;
      int err;
@@ -762,7 +763,7 @@ struct i915_ppgtt *gen8_ppgtt_create(struct intel_gt *gt)
      if (!ppgtt)
          return ERR_PTR(-ENOMEM);
  -    ppgtt_init(ppgtt, gt);
+    ppgtt_init(ppgtt, gt, lmem_pt_obj_flags);
      ppgtt->vm.top = i915_vm_is_4lvl(&ppgtt->vm) ? 3 : 2;
      ppgtt->vm.pd_shift = ilog2(SZ_4K * SZ_4K / sizeof(gen8_pte_t));
  diff --git a/drivers/gpu/drm/i915/gt/gen8_ppgtt.h b/drivers/gpu/drm/i915/gt/gen8_ppgtt.h
index b9028c2ad3c7..f541d19264b4 100644
--- a/drivers/gpu/drm/i915/gt/gen8_ppgtt.h
+++ b/drivers/gpu/drm/i915/gt/gen8_ppgtt.h
@@ -12,7 +12,9 @@ struct i915_address_space;
  struct intel_gt;
  enum i915_cache_level;
  -struct i915_ppgtt *gen8_ppgtt_create(struct intel_gt *gt);
+struct i915_ppgtt *gen8_ppgtt_create(struct intel_gt *gt,
+                     unsigned long lmem_pt_obj_flags);
+
  u64 gen8_ggtt_pte_encode(dma_addr_t addr,
               enum i915_cache_level level,
               u32 flags);
diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt.c b/drivers/gpu/drm/i915/gt/intel_ggtt.c
index 8d71f67926f1..06576fc1310e 100644
--- a/drivers/gpu/drm/i915/gt/intel_ggtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_ggtt.c
@@ -644,7 +644,7 @@ static int init_aliasing_ppgtt(struct i915_ggtt *ggtt)
      struct i915_ppgtt *ppgtt;
      int err;
  -    ppgtt = i915_ppgtt_create(ggtt->vm.gt);
+    ppgtt = i915_ppgtt_create(ggtt->vm.gt, 0);
      if (IS_ERR(ppgtt))
          return PTR_ERR(ppgtt);
  @@ -909,6 +909,7 @@ static int gen8_gmch_probe(struct i915_ggtt *ggtt)
          size = gen8_get_total_gtt_size(snb_gmch_ctl);
        ggtt->vm.alloc_pt_dma = alloc_pt_dma;
+    ggtt->vm.lmem_pt_obj_flags = I915_BO_ALLOC_PM_EARLY;

The scratch page is still in system memory for the ggtt, so I guess this is not needed? Although maybe that will change, so probably good to keep?

Hmm, yes, I guess lets keep this for a possible future audit for now. I think there are other vms that may not need this flag either.

Thanks for  reviewing!

/Thomas





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