On 22/06/2021 13:29, Thomas Hellström wrote:
On 6/22/21 2:15 PM, Matthew Auld wrote:
On Tue, 22 Jun 2021 at 11:11, Thomas Hellström
<thomas.hellstrom@xxxxxxxxxxxxxxx> wrote:
On 6/22/21 11:58 AM, Matthew Auld wrote:
Just checking the current region is not enough, if we later migrate the
object somewhere else. For example if the placements are {SMEM, LMEM},
then we might get this wrong. Another idea might be to make the
page_alignment part of the ttm_place, instead of the BO.
Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
index c5deb8b7227c..5d894bba6430 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
@@ -753,6 +753,25 @@ void i915_ttm_bo_destroy(struct
ttm_buffer_object *bo)
call_rcu(&obj->rcu, __i915_gem_free_object_rcu);
}
+static u64 i915_gem_object_page_size(struct drm_i915_gem_object *obj)
+{
+ u64 page_size;
+ int i;
+
+ if (!obj->mm.n_placements)
+ return obj->mm.region->min_page_size;
+
+ page_size = 0;
+ for (i = 0; i < obj->mm.n_placements; i++) {
+ struct intel_memory_region *mr = obj->mm.placements[i];
+
+ page_size = max_t(u64, mr->min_page_size, page_size);
+ }
+
+ GEM_BUG_ON(!page_size);
+ return page_size;
+}
+
/**
* __i915_gem_ttm_object_init - Initialize a ttm-backed i915 gem
object
* @mem: The initial memory region for the object.
@@ -793,7 +812,7 @@ int __i915_gem_ttm_object_init(struct
intel_memory_region *mem,
obj->base.vma_node.driver_private = i915_gem_to_ttm(obj);
ret = ttm_bo_init(&i915->bdev, i915_gem_to_ttm(obj), size,
bo_type, &i915_sys_placement,
- mem->min_page_size >> PAGE_SHIFT,
+ i915_gem_object_page_size(obj) >> PAGE_SHIFT,
Hmm, can't we just have the buddy manager silently enforce its
min_page_size?
Maybe, but we need some way of overriding it for all of our page-table
allocations(and some other stuff also), so being able to control the
page_alignment at the object level here seems reasonable? Could maybe
pass it through with create_lmem_with_page_size(..., page_size)? Ok,
it might be best to first type it and then see how it will all fit
together.
Hmm, OK, I'm not 100% sure what the various requirements are here on the
object level. But for region requirements, I think we've historically
enforced that through the manager, taking also the bo->page_alignment
into account and applying the larger of the two,
There is an example in vmw_thp_insert_aligned().
Yeah, so for our use case we need to support page_alignment <
min_page_size, for page-tables(4K). I guess pushing the min_page_size
into buddy_man, and then letting page_alignment override that, with the
added caveat that it can be smaller could work. Otherwise just using
mm.chunk_size would already fit the bill quite nicely.
/Thomas
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