Re: [PATCH v2 2/6] drm/i915/ttm: audit remaining bo->resource

["Das, Nirmoy" <nirmoy.das@xxxxxxxxxxxxxxx>]

On 1/30/2023 1:06 PM, Matthew Auld wrote:
> In the near future TTM will have NULL bo->resource when the object is
> initially created, plus after calling into pipeline-gutting. Try to
> handle the remaining cases. In practice NULL bo->resource should be
> taken to mean swapped-out or purged object.
>
> v2 (Andrzej):
>    - Rather make i915_ttm_cpu_maps_iomem() return false with NULL
>      resource.
>
> References: 516198d317d8 ("drm/i915: audit bo->resource usage v3")
> Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
> Cc: Christian König <ckoenig.leichtzumerken@xxxxxxxxx>
> Cc: Nirmoy Das <nirmoy.das@xxxxxxxxx>
> Reviewed-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>


Reviewed-by: Nirmoy Das <nirmoy.das@xxxxxxxxx>

> ---
>   drivers/gpu/drm/i915/gem/i915_gem_ttm.c      | 10 ++++++++--
>   drivers/gpu/drm/i915/gem/i915_gem_ttm.h      |  2 +-
>   drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c |  4 ++++
>   drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c   |  7 +++++--
>   4 files changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> index 4758f21c91e1..341b94672abc 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> @@ -472,7 +472,7 @@ static int i915_ttm_shrink(struct drm_i915_gem_object *obj, unsigned int flags)
>   	struct ttm_placement place = {};
>   	int ret;
>   
> -	if (!bo->ttm || bo->resource->mem_type != TTM_PL_SYSTEM)
> +	if (!bo->ttm || i915_ttm_cpu_maps_iomem(bo->resource))
>   		return 0;
>   
>   	GEM_BUG_ON(!i915_tt->is_shmem);
> @@ -511,7 +511,13 @@ static void i915_ttm_delete_mem_notify(struct ttm_buffer_object *bo)
>   {
>   	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
>   
> -	if (bo->resource && !i915_ttm_is_ghost_object(bo)) {
> +	/*
> +	 * This gets called twice by ttm, so long as we have a ttm resource or
> +	 * ttm_tt then we can still safely call this. Due to pipeline-gutting,
> +	 * we maybe have NULL bo->resource, but in that case we should always
> +	 * have a ttm alive (like if the pages are swapped out).
> +	 */
> +	if ((bo->resource || bo->ttm) && !i915_ttm_is_ghost_object(bo)) {
>   		__i915_gem_object_pages_fini(obj);
>   		i915_ttm_free_cached_io_rsgt(obj);
>   	}
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.h b/drivers/gpu/drm/i915/gem/i915_gem_ttm.h
> index 2a94a99ef76b..f8f6bed1b297 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.h
> @@ -98,7 +98,7 @@ static inline bool i915_ttm_gtt_binds_lmem(struct ttm_resource *mem)
>   static inline bool i915_ttm_cpu_maps_iomem(struct ttm_resource *mem)
>   {
>   	/* Once / if we support GGTT, this is also false for cached ttm_tts */
> -	return mem->mem_type != I915_PL_SYSTEM;
> +	return mem && mem->mem_type != I915_PL_SYSTEM;
>   }
>   
>   bool i915_ttm_resource_mappable(struct ttm_resource *res);
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
> index 76dd9e5e1a8b..d030182ca176 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
> @@ -711,6 +711,10 @@ int i915_gem_obj_copy_ttm(struct drm_i915_gem_object *dst,
>   
>   	assert_object_held(dst);
>   	assert_object_held(src);
> +
> +	if (GEM_WARN_ON(!src_bo->resource || !dst_bo->resource))
> +		return -EINVAL;
> +
>   	i915_deps_init(&deps, GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
>   
>   	ret = dma_resv_reserve_fences(src_bo->base.resv, 1);
> 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 7e67742bc65e..dfe39c8e74d8 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c
> @@ -53,7 +53,7 @@ static int i915_ttm_backup(struct i915_gem_apply_to_region *apply,
>   	unsigned int flags;
>   	int err = 0;
>   
> -	if (bo->resource->mem_type == I915_PL_SYSTEM || obj->ttm.backup)
> +	if (!i915_ttm_cpu_maps_iomem(bo->resource) || obj->ttm.backup)
>   		return 0;
>   
>   	if (pm_apply->allow_gpu && i915_gem_object_evictable(obj))
> @@ -187,7 +187,10 @@ static int i915_ttm_restore(struct i915_gem_apply_to_region *apply,
>   		return err;
>   
>   	/* Content may have been swapped. */
> -	err = ttm_tt_populate(backup_bo->bdev, backup_bo->ttm, &ctx);
> +	if (!backup_bo->resource)
> +		err = ttm_bo_validate(backup_bo, i915_ttm_sys_placement(), &ctx);
> +	if (!err)
> +		err = ttm_tt_populate(backup_bo->bdev, backup_bo->ttm, &ctx);
>   	if (!err) {
>   		err = i915_gem_obj_copy_ttm(obj, backup, pm_apply->allow_gpu,
>   					    false);