[PATCH 1/2] drm/i915: Don't allow setting I915_CONTEXT_PARAM_VM twice

[Daniel Vetter]

On Sat, Jul 10, 2021 at 04:24:46PM -0500, Jason Ekstrand wrote:
> Allowing setting it multiple times brings no real utility to the API, no
> userspace relies on it, and it does make i915 a tiny bit more
> complicated.  Let's disallow it for now unless someone comes up with a
> compelling reason to support it.

Maybe mention this is for symmetry with other proto ctx set_param
operations, like set_engines.

> 
> Signed-off-by: Jason Ekstrand <jason at jlekstrand.net>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>

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

> ---
>  drivers/gpu/drm/i915/gem/i915_gem_context.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> index 7d6f52d8a8012..5853737cc79f3 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -319,7 +319,6 @@ static int set_proto_ctx_vm(struct drm_i915_file_private *fpriv,
>  			    const struct drm_i915_gem_context_param *args)
>  {
>  	struct drm_i915_private *i915 = fpriv->dev_priv;
> -	struct i915_address_space *vm;
>  
>  	if (args->size)
>  		return -EINVAL;
> @@ -327,17 +326,16 @@ static int set_proto_ctx_vm(struct drm_i915_file_private *fpriv,
>  	if (!HAS_FULL_PPGTT(i915))
>  		return -ENODEV;
>  
> +	if (pc->vm)
> +		return -EINVAL;
> +
>  	if (upper_32_bits(args->value))
>  		return -ENOENT;
>  
> -	vm = i915_gem_vm_lookup(fpriv, args->value);
> -	if (!vm)
> +	pc->vm = i915_gem_vm_lookup(fpriv, args->value);
> +	if (!pc->vm)
>  		return -ENOENT;
>  
> -	if (pc->vm)
> -		i915_vm_put(pc->vm);
> -	pc->vm = vm;
> -
>  	return 0;
>  }
>  
> -- 
> 2.31.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch