[Intel-gfx] [PATCH 09/21] drm/i915/gem: Disallow creating contexts with too many engines

[Daniel Vetter]

On Fri, Apr 23, 2021 at 05:31:19PM -0500, Jason Ekstrand wrote:
> There's no sense in allowing userspace to create more engines than it
> can possibly access via execbuf.
> 
> Signed-off-by: Jason Ekstrand <jason at jlekstrand.net>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_context.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> index 5f8d0faf783aa..ecb3bf5369857 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -1640,11 +1640,10 @@ set_engines(struct i915_gem_context *ctx,
>  		return -EINVAL;
>  	}
>  
> -	/*
> -	 * Note that I915_EXEC_RING_MASK limits execbuf to only using the
> -	 * first 64 engines defined here.
> -	 */
>  	num_engines = (args->size - sizeof(*user)) / sizeof(*user->engines);

Maybe add a comment like /* RING_MASK has not shift, so can be used
directly here */ since I had to check that :-)

Same story about igt testcases needed, just to be sure.

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

> +	if (num_engines > I915_EXEC_RING_MASK + 1)
> +		return -EINVAL;
> +
>  	set.engines = alloc_engines(num_engines);
>  	if (!set.engines)
>  		return -ENOMEM;
> -- 
> 2.31.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch