Re: [Intel-gfx] [PATCH v11 5/5] drm/amdgpu: add drm buddy support to amdgpu

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 04.02.22 um 12:22 schrieb Arunpravin:
> On 28/01/22 7:48 pm, Matthew Auld wrote:
>> On Thu, 27 Jan 2022 at 14:11, Arunpravin
>> <Arunpravin.PaneerSelvam@amd.com> wrote:
>>> - Remove drm_mm references and replace with drm buddy functionalities
>>> - Add res cursor support for drm buddy
>>>
>>> v2(Matthew Auld):
>>>    - replace spinlock with mutex as we call kmem_cache_zalloc
>>>      (..., GFP_KERNEL) in drm_buddy_alloc() function
>>>
>>>    - lock drm_buddy_block_trim() function as it calls
>>>      mark_free/mark_split are all globally visible
>>>
>>> v3(Matthew Auld):
>>>    - remove trim method error handling as we address the failure case
>>>      at drm_buddy_block_trim() function
>>>
>>> v4:
>>>    - fix warnings reported by kernel test robot <lkp@intel.com>
>>>
>>> v5:
>>>    - fix merge conflict issue
>>>
>>> v6:
>>>    - fix warnings reported by kernel test robot <lkp@intel.com>
>>>
>>> Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam@amd.com>
>>> ---
>>>   drivers/gpu/drm/Kconfig                       |   1 +
>>>   .../gpu/drm/amd/amdgpu/amdgpu_res_cursor.h    |  97 +++++--
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h       |   7 +-
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c  | 259 ++++++++++--------
>>>   4 files changed, 231 insertions(+), 133 deletions(-)
>> <snip>
>>
>>> -/**
>>> - * amdgpu_vram_mgr_virt_start - update virtual start address
>>> - *
>>> - * @mem: ttm_resource to update
>>> - * @node: just allocated node
>>> - *
>>> - * Calculate a virtual BO start address to easily check if everything is CPU
>>> - * accessible.
>>> - */
>>> -static void amdgpu_vram_mgr_virt_start(struct ttm_resource *mem,
>>> -                                      struct drm_mm_node *node)
>>> -{
>>> -       unsigned long start;
>>> -
>>> -       start = node->start + node->size;
>>> -       if (start > mem->num_pages)
>>> -               start -= mem->num_pages;
>>> -       else
>>> -               start = 0;
>>> -       mem->start = max(mem->start, start);
>>> -}
>>> -
>>>   /**
>>>    * amdgpu_vram_mgr_new - allocate new ranges
>>>    *
>>> @@ -366,13 +357,13 @@ static int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
>>>                                 const struct ttm_place *place,
>>>                                 struct ttm_resource **res)
>>>   {
>>> -       unsigned long lpfn, num_nodes, pages_per_node, pages_left, pages;
>>> +       unsigned long lpfn, pages_per_node, pages_left, pages, n_pages;
>>> +       u64 vis_usage = 0, mem_bytes, max_bytes, min_page_size;
>>>          struct amdgpu_vram_mgr *mgr = to_vram_mgr(man);
>>>          struct amdgpu_device *adev = to_amdgpu_device(mgr);
>>> -       uint64_t vis_usage = 0, mem_bytes, max_bytes;
>>> -       struct ttm_range_mgr_node *node;
>>> -       struct drm_mm *mm = &mgr->mm;
>>> -       enum drm_mm_insert_mode mode;
>>> +       struct amdgpu_vram_mgr_node *node;
>>> +       struct drm_buddy *mm = &mgr->mm;
>>> +       struct drm_buddy_block *block;
>>>          unsigned i;
>>>          int r;
>>>
>>> @@ -391,10 +382,9 @@ static int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
>>>                  goto error_sub;
>>>          }
>>>
>>> -       if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
>>> +       if (place->flags & TTM_PL_FLAG_CONTIGUOUS)
>>>                  pages_per_node = ~0ul;
>>> -               num_nodes = 1;
>>> -       } else {
>>> +       else {
>>>   #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>>>                  pages_per_node = HPAGE_PMD_NR;
>>>   #else
>>> @@ -403,11 +393,9 @@ static int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
>>>   #endif
>>>                  pages_per_node = max_t(uint32_t, pages_per_node,
>>>                                         tbo->page_alignment);
>>> -               num_nodes = DIV_ROUND_UP_ULL(PFN_UP(mem_bytes), pages_per_node);
>>>          }
>>>
>>> -       node = kvmalloc(struct_size(node, mm_nodes, num_nodes),
>>> -                       GFP_KERNEL | __GFP_ZERO);
>>> +       node = kzalloc(sizeof(*node), GFP_KERNEL);
>>>          if (!node) {
>>>                  r = -ENOMEM;
>>>                  goto error_sub;
>>> @@ -415,9 +403,17 @@ static int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
>>>
>>>          ttm_resource_init(tbo, place, &node->base);
>>>
>>> -       mode = DRM_MM_INSERT_BEST;
>>> +       INIT_LIST_HEAD(&node->blocks);
>>> +
>>>          if (place->flags & TTM_PL_FLAG_TOPDOWN)
>>> -               mode = DRM_MM_INSERT_HIGH;
>>> +               node->flags |= DRM_BUDDY_TOPDOWN_ALLOCATION;
>>> +
>>> +       if (place->fpfn || lpfn != man->size)
>>> +               /* Allocate blocks in desired range */
>>> +               node->flags |= DRM_BUDDY_RANGE_ALLOCATION;
>>> +
>>> +       min_page_size = mgr->default_page_size;
>>> +       BUG_ON(min_page_size < mm->chunk_size);
>>>
>>>          pages_left = node->base.num_pages;
>>>
>>> @@ -425,36 +421,61 @@ static int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
>>>          pages = min(pages_left, 2UL << (30 - PAGE_SHIFT));
>>>
>>>          i = 0;
>>> -       spin_lock(&mgr->lock);
>>>          while (pages_left) {
>>> -               uint32_t alignment = tbo->page_alignment;
>>> -
>>>                  if (pages >= pages_per_node)
>>> -                       alignment = pages_per_node;
>>> -
>>> -               r = drm_mm_insert_node_in_range(mm, &node->mm_nodes[i], pages,
>>> -                                               alignment, 0, place->fpfn,
>>> -                                               lpfn, mode);
>>> -               if (unlikely(r)) {
>>> -                       if (pages > pages_per_node) {
>>> -                               if (is_power_of_2(pages))
>>> -                                       pages = pages / 2;
>>> -                               else
>>> -                                       pages = rounddown_pow_of_two(pages);
>>> -                               continue;
>>> -                       }
>>> -                       goto error_free;
>>> +                       pages = pages_per_node;
>>> +
>>> +               n_pages = pages;
>>> +
>>> +               if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
>>> +                       n_pages = roundup_pow_of_two(n_pages);
>>> +                       min_page_size = (u64)n_pages << PAGE_SHIFT;
>>> +
>>> +                       if (n_pages > lpfn)
>>> +                               lpfn = n_pages;
>>>                  }
>>>
>>> -               vis_usage += amdgpu_vram_mgr_vis_size(adev, &node->mm_nodes[i]);
>>> -               amdgpu_vram_mgr_virt_start(&node->base, &node->mm_nodes[i]);
>>> +               mutex_lock(&mgr->lock);
>>> +               r = drm_buddy_alloc_blocks(mm, (u64)place->fpfn << PAGE_SHIFT,
>>> +                                          (u64)lpfn << PAGE_SHIFT,
>>> +                                          (u64)n_pages << PAGE_SHIFT,
>>> +                                          min_page_size,
>>> +                                          &node->blocks,
>>> +                                          node->flags);
>>> +               mutex_unlock(&mgr->lock);
>>> +               if (unlikely(r))
>>> +                       goto error_free_blocks;
>>> +
>>>                  pages_left -= pages;
>>>                  ++i;
>>>
>>>                  if (pages > pages_left)
>>>                          pages = pages_left;
>>>          }
>>> -       spin_unlock(&mgr->lock);
>>> +
>>> +       /* Free unused pages for contiguous allocation */
>>> +       if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
>>> +               u64 actual_size = (u64)node->base.num_pages << PAGE_SHIFT;
>>> +
>>> +               mutex_lock(&mgr->lock);
>>> +               drm_buddy_block_trim(mm,
>>> +                                    actual_size,
>>> +                                    &node->blocks);
>>> +               mutex_unlock(&mgr->lock);
>>> +       }
>>> +
>>> +       list_for_each_entry(block, &node->blocks, link)
>>> +               vis_usage += amdgpu_vram_mgr_vis_size(adev, block);
>>> +
>>> +       block = list_first_entry_or_null(&node->blocks,
>>> +                                        struct drm_buddy_block,
>>> +                                        link);
>>> +       if (!block) {
>>> +               r = -ENOENT;
>>> +               goto error_free_res;
>>> +       }
>>> +
>>> +       node->base.start = amdgpu_node_start(block) >> PAGE_SHIFT;
>> Hmm, does this work? It looks like there are various places checking
>> that res->start + res->num_pages <= visible_size, which IIUC should
>> only return true when the entire object is placed in the mappable
>> portion. i915 is doing something similar. Also it looks like
>> ttm_resource_compat() is potentially relying on this, like when moving
>> something from non-mappable -> mappable in
>> amdgpu_bo_fault_reserve_notify()?
>>
>> Perhaps something like:
>>
>> if (vis_usage == num_pages)
>>      base.start = 0;
>> else
>>      base.start = visible_size;
>>
>> Otherwise I guess just keep amdgpu_vram_mgr_virt_start()?
>>
> hmm, I wonder how it works, may be we didn't go through the corner case
> where res->start + res->num_pages > visible_size
>
> in amdgpu if AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED flag is enabled, we
> set the ttm_place.lpfn = visible_pfn at
> amdgpu_bo_placement_from_domain(). Hence, in amdgpu_vram_mgr_new()
> function DRM_BUDDY_RANGE_ALLOCATION flag is enabled, which calls the
> alloc_range_bias() in drm_buddy.c.
>
> Here we get blocks chained together in random order complying
> visible_pfn range. say for instance num_pages = 13
> we may get,
> Block 1 addr - 500 (order-3)
> Block 2 addr - 400 (order-2)
> Block 3 addr - 600 (order-0)
>
> I think currently base.start = Block 1 start address fetched from the
> list and the address 500 assigned to it, which is good for the resource
> access since we access the blocks using the list link
>
> But for the check res->start + res->num_pages <= visible_size in few
> places, this doesn't work. AFAIK, keeping amdgpu_vram_mgr_virt_start()
> doesn't work since the function looks for nodes in continuous address to
> calculate the start address. AFAIK, assigning the start address (400 +
> num_pages <= visible_size) mislead in our case since we use linked list
>
> how about replacing the check with a bool type return function which
> checks the each block start address + block size <= visible_size?

Yeah, we already have that in the TTM code. It's just not used 
everywhere IIRC.

The node->start can just be set to the invalid offset for now and should 
be removed as soon as we don't need it any more.

Regards,
Christian.