Re: [PATCH v2 3/8] drm/i915/gtt: add gtt mappable plumbing

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On 03/12/2021 17:25, Ramalingam C wrote:
On 2021-12-03 at 12:24:21 +0000, Matthew Auld wrote:
With object clearing/copying we need to be able to modify the PTEs on
the fly via some batch buffer, which means we need to be able to map the
paging structures(or at the very least the PT, but being able to also
map the PD might also be useful at some point) into the GTT. And since
the paging structures must reside in LMEM on discrete, we need to ensure
that these objects have correct physical alignment, as per any min page
restrictions, like on DG2. This is potentially costly, but this should
be limited to the special migrate_vm, which only needs to a few fixed
sized windows.

Matt,

Just a thought. instead of classifying whole ppgtt as VM_GTT_MAPPABLE
and rounding up the pt size to min_page_size,
could we just add size of pt as parameter into i915_vm_alloc_pt_stash
and alloc_pt, which can be used for vm->alloc_pt_dma() instead of
I915_GTT_PAGE_SIZE_4K.

But PT for a smem entries also needs to be 64k aligned to be mapped into
the GTT right? So no advantage of having the pt_stash level physical
alignment..

Any thoughts on this line?

Yes, this sounds like a good idea. Initially I was worried about stuff like gen8_alloc_top_pd() which would skip this, but it looks like we only really care about the PT and maybe also the PD having correct alignment. Will change.


Ram


Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Cc: Ramalingam C <ramalingam.c@xxxxxxxxx>
---
  drivers/gpu/drm/i915/gem/i915_gem_context.c     |  4 ++--
  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            |  3 ++-
  drivers/gpu/drm/i915/gt/gen8_ppgtt.h            |  1 +
  drivers/gpu/drm/i915/gt/intel_ggtt.c            |  2 +-
  drivers/gpu/drm/i915/gt/intel_gt.c              |  2 +-
  drivers/gpu/drm/i915/gt/intel_gtt.c             |  7 +++++++
  drivers/gpu/drm/i915/gt/intel_gtt.h             |  9 +++++++++
  drivers/gpu/drm/i915/gt/intel_migrate.c         |  4 +++-
  drivers/gpu/drm/i915/gt/intel_ppgtt.c           | 17 ++++++++++++-----
  drivers/gpu/drm/i915/gt/selftest_hangcheck.c    |  2 +-
  drivers/gpu/drm/i915/gvt/scheduler.c            |  2 +-
  drivers/gpu/drm/i915/selftests/i915_gem_gtt.c   |  4 ++--
  14 files changed, 44 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index ebd775cb1661..b394954726b0 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -1559,7 +1559,7 @@ 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, 0);
+		ppgtt = i915_ppgtt_create(&i915->gt, 0, 0);
  		if (IS_ERR(ppgtt)) {
  			drm_dbg(&i915->drm, "PPGTT setup failed (%ld)\n",
  				PTR_ERR(ppgtt));
@@ -1742,7 +1742,7 @@ int i915_gem_vm_create_ioctl(struct drm_device *dev, void *data,
  	if (args->flags)
  		return -EINVAL;
- ppgtt = i915_ppgtt_create(&i915->gt, 0);
+	ppgtt = i915_ppgtt_create(&i915->gt, 0, 0);
  	if (IS_ERR(ppgtt))
  		return PTR_ERR(ppgtt);
diff --git a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
index bd8dc1a28022..c1b86c7a4754 100644
--- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
+++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
@@ -1764,7 +1764,7 @@ 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, 0);
+	ppgtt = i915_ppgtt_create(&dev_priv->gt, 0, 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 c0d149f04949..778472e563aa 100644
--- a/drivers/gpu/drm/i915/gt/gen6_ppgtt.c
+++ b/drivers/gpu/drm/i915/gt/gen6_ppgtt.c
@@ -443,7 +443,7 @@ struct i915_ppgtt *gen6_ppgtt_create(struct intel_gt *gt)
mutex_init(&ppgtt->flush); - ppgtt_init(&ppgtt->base, gt, 0);
+	ppgtt_init(&ppgtt->base, gt, 0, 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 312b2267bf87..dfca803b4ff1 100644
--- a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
+++ b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
@@ -912,6 +912,7 @@ gen8_alloc_top_pd(struct i915_address_space *vm)
   *
   */
  struct i915_ppgtt *gen8_ppgtt_create(struct intel_gt *gt,
+				     unsigned long vm_flags,
  				     unsigned long lmem_pt_obj_flags)
  {
  	struct i915_ppgtt *ppgtt;
@@ -921,7 +922,7 @@ struct i915_ppgtt *gen8_ppgtt_create(struct intel_gt *gt,
  	if (!ppgtt)
  		return ERR_PTR(-ENOMEM);
- ppgtt_init(ppgtt, gt, lmem_pt_obj_flags);
+	ppgtt_init(ppgtt, gt, vm_flags, 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 f541d19264b4..c0af12593576 100644
--- a/drivers/gpu/drm/i915/gt/gen8_ppgtt.h
+++ b/drivers/gpu/drm/i915/gt/gen8_ppgtt.h
@@ -13,6 +13,7 @@ struct intel_gt;
  enum i915_cache_level;
struct i915_ppgtt *gen8_ppgtt_create(struct intel_gt *gt,
+				     unsigned long vm_flags,
  				     unsigned long lmem_pt_obj_flags);
u64 gen8_ggtt_pte_encode(dma_addr_t addr,
diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt.c b/drivers/gpu/drm/i915/gt/intel_ggtt.c
index 47f88f031749..938af60fd32f 100644
--- a/drivers/gpu/drm/i915/gt/intel_ggtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_ggtt.c
@@ -661,7 +661,7 @@ static int init_aliasing_ppgtt(struct i915_ggtt *ggtt)
  	struct i915_ppgtt *ppgtt;
  	int err;
- ppgtt = i915_ppgtt_create(ggtt->vm.gt, 0);
+	ppgtt = i915_ppgtt_create(ggtt->vm.gt, 0, 0);
  	if (IS_ERR(ppgtt))
  		return PTR_ERR(ppgtt);
diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
index 510cda6a163f..991a514a1dc3 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -484,7 +484,7 @@ static void intel_gt_fini_scratch(struct intel_gt *gt)
  static struct i915_address_space *kernel_vm(struct intel_gt *gt)
  {
  	if (INTEL_PPGTT(gt->i915) > INTEL_PPGTT_ALIASING)
-		return &i915_ppgtt_create(gt, I915_BO_ALLOC_PM_EARLY)->vm;
+		return &i915_ppgtt_create(gt, 0, I915_BO_ALLOC_PM_EARLY)->vm;
  	else
  		return i915_vm_get(&gt->ggtt->vm);
  }
diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.c b/drivers/gpu/drm/i915/gt/intel_gtt.c
index 5447615fc6f3..d9bf53dc1d85 100644
--- a/drivers/gpu/drm/i915/gt/intel_gtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gtt.c
@@ -18,6 +18,13 @@ struct drm_i915_gem_object *alloc_pt_lmem(struct i915_address_space *vm, int sz)
  {
  	struct drm_i915_gem_object *obj;
+ if (vm->vm_flags & I915_VM_GTT_MAPPABLE) {
+		struct intel_memory_region *mr =
+			vm->i915->mm.regions[INTEL_REGION_LMEM];
+
+		sz = max_t(int, sz, mr->min_page_size);
+	}
+
  	/*
  	 * To avoid severe over-allocation when dealing with min_page_size
  	 * restrictions, we override that behaviour here by allowing an object
diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.h b/drivers/gpu/drm/i915/gt/intel_gtt.h
index cbc0b5266cb4..eee97b46a1f9 100644
--- a/drivers/gpu/drm/i915/gt/intel_gtt.h
+++ b/drivers/gpu/drm/i915/gt/intel_gtt.h
@@ -266,6 +266,13 @@ struct i915_address_space {
  	u8 pd_shift;
  	u8 scratch_order;
+/*
+ * Paging structures are going to accessed via the GTT itself, and therefore
+ * might need special alignment.
+ */
+#define I915_VM_GTT_MAPPABLE BIT(0)
+	unsigned long vm_flags;
+
  	/* Flags used when creating page-table objects for this vm */
  	unsigned long lmem_pt_obj_flags;
@@ -543,6 +550,7 @@ i915_page_dir_dma_addr(const struct i915_ppgtt *ppgtt, const unsigned int n)
  }
void ppgtt_init(struct i915_ppgtt *ppgtt, struct intel_gt *gt,
+		unsigned long vm_flags,
  		unsigned long lmem_pt_obj_flags);
int i915_ggtt_probe_hw(struct drm_i915_private *i915);
@@ -562,6 +570,7 @@ static inline bool i915_ggtt_has_aperture(const struct i915_ggtt *ggtt)
  int i915_ppgtt_init_hw(struct intel_gt *gt);
struct i915_ppgtt *i915_ppgtt_create(struct intel_gt *gt,
+				     unsigned long vm_flags,
  				     unsigned long lmem_pt_obj_flags);
void i915_ggtt_suspend_vm(struct i915_address_space *vm);
diff --git a/drivers/gpu/drm/i915/gt/intel_migrate.c b/drivers/gpu/drm/i915/gt/intel_migrate.c
index 2d3188a398dd..d553b76b1168 100644
--- a/drivers/gpu/drm/i915/gt/intel_migrate.c
+++ b/drivers/gpu/drm/i915/gt/intel_migrate.c
@@ -78,7 +78,9 @@ static struct i915_address_space *migrate_vm(struct intel_gt *gt)
  	 * TODO: Add support for huge LMEM PTEs
  	 */
- vm = i915_ppgtt_create(gt, I915_BO_ALLOC_PM_EARLY);
+	vm = i915_ppgtt_create(gt,
+			       I915_VM_GTT_MAPPABLE,
+			       I915_BO_ALLOC_PM_EARLY);
  	if (IS_ERR(vm))
  		return ERR_CAST(vm);
diff --git a/drivers/gpu/drm/i915/gt/intel_ppgtt.c b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
index b8238f5bc8b1..1218024dfd57 100644
--- a/drivers/gpu/drm/i915/gt/intel_ppgtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
@@ -156,20 +156,25 @@ int i915_ppgtt_init_hw(struct intel_gt *gt)
  }
static struct i915_ppgtt *
-__ppgtt_create(struct intel_gt *gt, unsigned long lmem_pt_obj_flags)
+__ppgtt_create(struct intel_gt *gt,
+	       unsigned long vm_flags,
+	       unsigned long lmem_pt_obj_flags)
  {
-	if (GRAPHICS_VER(gt->i915) < 8)
+	if (GRAPHICS_VER(gt->i915) < 8) {
+		WARN_ON_ONCE(vm_flags);
  		return gen6_ppgtt_create(gt);
-	else
-		return gen8_ppgtt_create(gt, lmem_pt_obj_flags);
+	} else {
+		return gen8_ppgtt_create(gt, vm_flags, lmem_pt_obj_flags);
+	}
  }
struct i915_ppgtt *i915_ppgtt_create(struct intel_gt *gt,
+				     unsigned long vm_flags,
  				     unsigned long lmem_pt_obj_flags)
  {
  	struct i915_ppgtt *ppgtt;
- ppgtt = __ppgtt_create(gt, lmem_pt_obj_flags);
+	ppgtt = __ppgtt_create(gt, vm_flags, lmem_pt_obj_flags);
  	if (IS_ERR(ppgtt))
  		return ppgtt;
@@ -301,6 +306,7 @@ int ppgtt_set_pages(struct i915_vma *vma)
  }
void ppgtt_init(struct i915_ppgtt *ppgtt, struct intel_gt *gt,
+		unsigned long vm_flags,
  		unsigned long lmem_pt_obj_flags)
  {
  	struct drm_i915_private *i915 = gt->i915;
@@ -309,6 +315,7 @@ void ppgtt_init(struct i915_ppgtt *ppgtt, struct intel_gt *gt,
  	ppgtt->vm.i915 = i915;
  	ppgtt->vm.dma = i915->drm.dev;
  	ppgtt->vm.total = BIT_ULL(INTEL_INFO(i915)->ppgtt_size);
+	ppgtt->vm.vm_flags = vm_flags;
  	ppgtt->vm.lmem_pt_obj_flags = lmem_pt_obj_flags;
dma_resv_init(&ppgtt->vm._resv);
diff --git a/drivers/gpu/drm/i915/gt/selftest_hangcheck.c b/drivers/gpu/drm/i915/gt/selftest_hangcheck.c
index e5ad4d5a91c0..8c299189e9cb 100644
--- a/drivers/gpu/drm/i915/gt/selftest_hangcheck.c
+++ b/drivers/gpu/drm/i915/gt/selftest_hangcheck.c
@@ -1600,7 +1600,7 @@ static int igt_reset_evict_ppgtt(void *arg)
  	if (INTEL_PPGTT(gt->i915) < INTEL_PPGTT_FULL)
  		return 0;
- ppgtt = i915_ppgtt_create(gt, 0);
+	ppgtt = i915_ppgtt_create(gt, 0, 0);
  	if (IS_ERR(ppgtt))
  		return PTR_ERR(ppgtt);
diff --git a/drivers/gpu/drm/i915/gvt/scheduler.c b/drivers/gpu/drm/i915/gvt/scheduler.c
index 6c804102528b..d726eee3aba5 100644
--- a/drivers/gpu/drm/i915/gvt/scheduler.c
+++ b/drivers/gpu/drm/i915/gvt/scheduler.c
@@ -1386,7 +1386,7 @@ int intel_vgpu_setup_submission(struct intel_vgpu *vgpu)
  	enum intel_engine_id i;
  	int ret;
- ppgtt = i915_ppgtt_create(&i915->gt, I915_BO_ALLOC_PM_EARLY);
+	ppgtt = i915_ppgtt_create(&i915->gt, 0, I915_BO_ALLOC_PM_EARLY);
  	if (IS_ERR(ppgtt))
  		return PTR_ERR(ppgtt);
diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c b/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c
index fdb4bf88293b..3bcd2bb85d10 100644
--- a/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c
@@ -155,7 +155,7 @@ static int igt_ppgtt_alloc(void *arg)
  	if (!HAS_PPGTT(dev_priv))
  		return 0;
- ppgtt = i915_ppgtt_create(&dev_priv->gt, 0);
+	ppgtt = i915_ppgtt_create(&dev_priv->gt, 0, 0);
  	if (IS_ERR(ppgtt))
  		return PTR_ERR(ppgtt);
@@ -1083,7 +1083,7 @@ static int exercise_ppgtt(struct drm_i915_private *dev_priv,
  	if (IS_ERR(file))
  		return PTR_ERR(file);
- ppgtt = i915_ppgtt_create(&dev_priv->gt, 0);
+	ppgtt = i915_ppgtt_create(&dev_priv->gt, 0, 0);
  	if (IS_ERR(ppgtt)) {
  		err = PTR_ERR(ppgtt);
  		goto out_free;
--
2.31.1




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