Re: [RFC PATCH 1/5] drm/xe: Implement VRAM object tracking ability using physical address

[Matthew Brost <matthew.brost@intel.com>]

On Wed, Feb 11, 2026 at 10:31:34AM +0530, Tejas Upadhyay wrote:

It will take a bit of time to get through this but spotted an issue.

> Implement the capability to track and identify TTM buffer objects
> using a specific faulty memory address in VRAM. This functionality
> is critical for supporting the memory page offline feature on CRI,
> where identified faulty pages must be traced back to their
> originating buffer for safe removal.
> 
> Signed-off-by: Tejas Upadhyay <tejas.upadhyay@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_ttm_vram_mgr.c | 75 ++++++++++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_ttm_vram_mgr.h |  2 +-
>  2 files changed, 76 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
> index d6aa61e55f4d..4e852eed5170 100644
> --- a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
> +++ b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
> @@ -56,6 +56,7 @@ static int xe_ttm_vram_mgr_new(struct ttm_resource_manager *man,
>  	u64 size, min_page_size;
>  	unsigned long lpfn;
>  	int err;
> +	struct drm_buddy_block *block;
>  
>  	lpfn = place->lpfn;
>  	if (!lpfn || lpfn > man->size >> PAGE_SHIFT)
> @@ -137,6 +138,8 @@ static int xe_ttm_vram_mgr_new(struct ttm_resource_manager *man,
>  	}
>  
>  	mgr->visible_avail -= vres->used_visible_size;
> +	list_for_each_entry(block, &vres->blocks, link)
> +		block->private = tbo;
>  	mutex_unlock(&mgr->lock);
>  
>  	if (!(vres->base.placement & TTM_PL_FLAG_CONTIGUOUS) &&
> @@ -467,3 +470,75 @@ u64 xe_ttm_vram_get_avail(struct ttm_resource_manager *man)
>  
>  	return avail;
>  }
> +
> +static inline bool overlaps(u64 s1, u64 e1, u64 s2, u64 e2)
> +{
> +	return s1 <= e2 && e1 >= s2;
> +}
> +
> +static inline bool contains(u64 s1, u64 e1, u64 s2, u64 e2)
> +{
> +	return s1 <= s2 && e1 <= e2;
> +}
> +
> +static struct ttm_buffer_object *xe_ttm_vram_addr_to_tbo(struct drm_buddy *mm, u64 start)
> +{
> +	struct drm_buddy_block *block;
> +	u64 end;
> +	LIST_HEAD(dfs);
> +	int i;
> +
> +	end = start + SZ_4K - 1;
> +	for (i = 0; i < mm->n_roots; ++i)
> +		list_add_tail(&mm->roots[i]->tmp_link, &dfs);
> +
> +	do {
> +		u64 block_start;
> +		u64 block_end;
> +
> +		block = list_first_entry_or_null(&dfs,
> +						 struct drm_buddy_block,
> +						 tmp_link);
> +		if (!block)
> +			break;
> +
> +		list_del(&block->tmp_link);
> +
> +		block_start = drm_buddy_block_offset(block);
> +		block_end = block_start + drm_buddy_block_size(mm, block) - 1;
> +
> +		if (!overlaps(start, end, block_start, block_end))
> +			continue;
> +
> +		if (contains(start, end, block_start, block_end) &&
> +		    !drm_buddy_block_is_split(block)) {
> +			if (drm_buddy_block_is_free(block)) {
> +				return NULL;
> +			} else if (drm_buddy_block_is_allocated(block) && !mm->clear_avail) {
> +				struct ttm_buffer_object *tbo = block->private;

The SVM code sets block->private to 'struct xe_vram_region' but we
definitely don't need too as there are other ways to look this up. Want
to fixup xe_svm.c in an independent patch to setting or looking at
block->private?

Matt

> +
> +				WARN_ON(!tbo);
> +				return tbo;
> +			}
> +		}
> +
> +		if (drm_buddy_block_is_split(block)) {
> +			list_add(&block->right->tmp_link, &dfs);
> +			list_add(&block->left->tmp_link, &dfs);
> +		}
> +	} while (1);
> +
> +	return NULL;
> +}
> +
> +int xe_ttm_tbo_handle_addr_fault(struct xe_tile *tile, unsigned long addr)
> +{
> +	struct xe_ttm_vram_mgr *vram_mgr = &tile->mem.vram->ttm;
> +	struct drm_buddy mm = vram_mgr->mm;
> +	struct ttm_buffer_object *tbo;
> +
> +	tbo = xe_ttm_vram_addr_to_tbo(&mm, addr);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(xe_ttm_tbo_handle_addr_fault);
> diff --git a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.h b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.h
> index 87b7fae5edba..1d6075411ebf 100644
> --- a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.h
> +++ b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.h
> @@ -30,7 +30,7 @@ u64 xe_ttm_vram_get_avail(struct ttm_resource_manager *man);
>  u64 xe_ttm_vram_get_cpu_visible_size(struct ttm_resource_manager *man);
>  void xe_ttm_vram_get_used(struct ttm_resource_manager *man,
>  			  u64 *used, u64 *used_visible);
> -
> +int xe_ttm_tbo_handle_addr_fault(struct xe_tile *tile, unsigned long addr);
>  static inline struct xe_ttm_vram_mgr_resource *
>  to_xe_ttm_vram_mgr_resource(struct ttm_resource *res)
>  {
> -- 
> 2.52.0
>