[Intel-gfx] [PATCH] drm/i915/gtt: Relax assertion for pt_used

[Mika Kuoppala]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> When inserting the final level PTE, we check that we are not overflowing
> the page table (checking that pt_used does not exceed the size of the
> table). However, we have to allow for every other PTE to be pinned by a
> simultaneous removal thread (as on remove we bump the pt_used counter
> before adjusting the table).
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>

Reviewed-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>

> ---
>  drivers/gpu/drm/i915/i915_gem_gtt.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index 081c8b79c047..94712d3eb882 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -1112,7 +1112,8 @@ static int __gen8_ppgtt_alloc(struct i915_address_space * const vm,
>  			    atomic_read(&pt->used));
>  
>  			atomic_add(count, &pt->used);
> -			GEM_BUG_ON(atomic_read(&pt->used) > I915_PDES);
> +			/* All other pdes may be simultaneously removed */
> +			GEM_BUG_ON(atomic_read(&pt->used) > 2 * I915_PDES);
>  			*start += count;
>  		}
>  	} while (idx++, --len);
> -- 
> 2.23.0.rc1