Re: [PATCH 18/20] drm/i915/uapi: forbid ALLOC_TOPDOWN for error capture

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

On 1/26/22 16:21, Matthew Auld wrote:
> On platforms where there might be non-mappable LMEM, force userspace to
> mark the buffers with the correct hint. When dumping the BO contents
> during capture we need CPU access. Note this only applies to buffers
> that can be placed in LMEM, and also doesn't impact DG1.

Oddly enough this seems to break DG1. We probably need to understand why.

/Thomas



>
> Signed-off-by: Matthew Auld <matthew.auld@intel.com>
> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> ---
>   drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> index 498b458fd784..3c8083852620 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> @@ -1965,7 +1965,7 @@ eb_find_first_request_added(struct i915_execbuffer *eb)
>   #if IS_ENABLED(CONFIG_DRM_I915_CAPTURE_ERROR)
>   
>   /* Stage with GFP_KERNEL allocations before we enter the signaling critical path */
> -static void eb_capture_stage(struct i915_execbuffer *eb)
> +static int eb_capture_stage(struct i915_execbuffer *eb)
>   {
>   	const unsigned int count = eb->buffer_count;
>   	unsigned int i = count, j;
> @@ -1978,6 +1978,9 @@ static void eb_capture_stage(struct i915_execbuffer *eb)
>   		if (!(flags & EXEC_OBJECT_CAPTURE))
>   			continue;
>   
> +		if (vma->obj->flags & I915_BO_ALLOC_TOPDOWN)
> +			return -EINVAL;
> +
>   		for_each_batch_create_order(eb, j) {
>   			struct i915_capture_list *capture;
>   
> @@ -1990,6 +1993,8 @@ static void eb_capture_stage(struct i915_execbuffer *eb)
>   			eb->capture_lists[j] = capture;
>   		}
>   	}
> +
> +	return 0;
>   }
>   
>   /* Commit once we're in the critical path */
> @@ -3418,7 +3423,9 @@ i915_gem_do_execbuffer(struct drm_device *dev,
>   	}
>   
>   	ww_acquire_done(&eb.ww.ctx);
> -	eb_capture_stage(&eb);
> +	err = eb_capture_stage(&eb);
> +	if (err)
> +		goto err_vma;
>   
>   	out_fence = eb_requests_create(&eb, in_fence, out_fence_fd);
>   	if (IS_ERR(out_fence)) {