[Intel-gfx] [PATCH] drm/i915: Fix pages pin counting around swizzle quirk

[Chris Wilson]

On Wed, Nov 02, 2016 at 09:43:54AM +0000, Chris Wilson wrote:
> commit bc0629a76726 ("drm/i915: Track pages pinned due to swizzling
> quirk") fixed one problem, but revealed a whole lot more. The root cause
> of the pin count mismatch for the swizzle quirk (for L-shaped memory on
> gen3/4) was that we were incrementing the pages_pin_count upon getting
> the backing pages but then overwriting the pages_pin_count to set it to
> 1 afterwards. With a little bit of adjustment to satisfy the GEM_BUG_ON
> sanitychecks, the fix is to replace the explicit atomic_set with an
> atomic_inc.
> 
> Fixes: 1233e2db199d ("drm/i915: Move object backing storage manipulation")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Ping?

> ---
>  drivers/gpu/drm/i915/i915_gem.c        | 40 ++++++++++++++++++----------------
>  drivers/gpu/drm/i915/i915_gem_gtt.c    |  1 +
>  drivers/gpu/drm/i915/i915_gem_tiling.c |  1 +
>  3 files changed, 23 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 993fb90da104..5fe7562aefbd 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2386,12 +2386,6 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
>  	if (i915_gem_object_needs_bit17_swizzle(obj))
>  		i915_gem_object_do_bit_17_swizzle(obj, st);
>  
> -	if (i915_gem_object_is_tiled(obj) &&
> -	    dev_priv->quirks & QUIRK_PIN_SWIZZLED_PAGES) {
> -		__i915_gem_object_pin_pages(obj);
> -		obj->mm.quirked = true;
> -	}
> -
>  	return st;
>  
>  err_pages:
> @@ -2424,6 +2418,13 @@ void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
>  	obj->mm.get_page.sg_idx = 0;
>  
>  	obj->mm.pages = pages;
> +
> +	if (i915_gem_object_is_tiled(obj) &&
> +	    to_i915(obj->base.dev)->quirks & QUIRK_PIN_SWIZZLED_PAGES) {
> +		GEM_BUG_ON(obj->mm.quirked);
> +		__i915_gem_object_pin_pages(obj);
> +		obj->mm.quirked = true;
> +	}
>  }
>  
>  static int ____i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
> @@ -2458,17 +2459,16 @@ int __i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
>  	if (err)
>  		return err;
>  
> -	if (likely(obj->mm.pages)) {
> -		__i915_gem_object_pin_pages(obj);
> -		goto unlock;
> -	}
> -
> -	GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
> +	if (unlikely(!obj->mm.pages)) {
> +		GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
> +		err = ____i915_gem_object_get_pages(obj);
> +		if (err)
> +			goto unlock;
>  
> -	err = ____i915_gem_object_get_pages(obj);
> -	if (!err)
> -		atomic_set_release(&obj->mm.pages_pin_count, 1);
> +		smp_mb__before_atomic();
> +	}
>  
> +	__i915_gem_object_pin_pages(obj);
>  unlock:
>  	mutex_unlock(&obj->mm.lock);
>  	return err;
> @@ -2542,8 +2542,8 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
>  		if (ret)
>  			goto err_unlock;
>  
> -		GEM_BUG_ON(atomic_read(&obj->mm.pages_pin_count));
> -		atomic_set_release(&obj->mm.pages_pin_count, 1);
> +		smp_mb__before_atomic();
> +		__i915_gem_object_pin_pages(obj);
>  		pinned = false;
>  	}
>  	GEM_BUG_ON(!obj->mm.pages);
> @@ -2578,7 +2578,7 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
>  	return ptr;
>  
>  err_unpin:
> -	atomic_dec(&obj->mm.pages_pin_count);
> +	__i915_gem_object_unpin_pages(obj);
>  err_unlock:
>  	ptr = ERR_PTR(ret);
>  	goto out_unlock;
> @@ -2996,7 +2996,7 @@ int i915_vma_unbind(struct i915_vma *vma)
>  		goto destroy;
>  
>  	GEM_BUG_ON(obj->bind_count == 0);
> -	GEM_BUG_ON(!obj->mm.pages);
> +	GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
>  
>  	if (i915_vma_is_map_and_fenceable(vma)) {
>  		/* release the fence reg _after_ flushing */
> @@ -3230,6 +3230,7 @@ i915_vma_insert(struct i915_vma *vma, u64 size, u64 alignment, u64 flags)
>  	list_move_tail(&obj->global_list, &dev_priv->mm.bound_list);
>  	list_move_tail(&vma->vm_link, &vma->vm->inactive_list);
>  	obj->bind_count++;
> +	GEM_BUG_ON(atomic_read(&obj->mm.pages_pin_count) < obj->bind_count);
>  
>  	return 0;
>  
> @@ -4282,6 +4283,7 @@ i915_gem_madvise_ioctl(struct drm_device *dev, void *data,
>  			obj->mm.quirked = false;
>  		}
>  		if (args->madv == I915_MADV_WILLNEED) {
> +			GEM_BUG_ON(obj->mm.quirked);
>  			__i915_gem_object_pin_pages(obj);
>  			obj->mm.quirked = true;
>  		}
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index dfc40f16f149..4dc1a463ef4c 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -3707,6 +3707,7 @@ i915_get_ggtt_vma_pages(struct i915_vma *vma)
>  {
>  	int ret = 0;
>  
> +	GEM_BUG_ON(!i915_gem_object_has_pinned_pages(vma->obj));
>  	if (vma->pages)
>  		return 0;
>  
> diff --git a/drivers/gpu/drm/i915/i915_gem_tiling.c b/drivers/gpu/drm/i915/i915_gem_tiling.c
> index 1577e7810cd6..251d51b01174 100644
> --- a/drivers/gpu/drm/i915/i915_gem_tiling.c
> +++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
> @@ -269,6 +269,7 @@ i915_gem_set_tiling(struct drm_device *dev, void *data,
>  					obj->mm.quirked = false;
>  				}
>  				if (!i915_gem_object_is_tiled(obj)) {
> +					GEM_BUG_ON(!obj->mm.quirked);
>  					__i915_gem_object_pin_pages(obj);
>  					obj->mm.quirked = true;
>  				}
> -- 
> 2.10.2
> 

-- 
Chris Wilson, Intel Open Source Technology Centre