[Intel-gfx] [PATCH 9/9] drm/i915: Mark imported dma-buf objects as being coherent

[Mika Kuoppala]

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

> A foreign dma-buf does not share our cache domain tracking, and we rely
> on the producer ensuring cache coherency. Marking them as being in the
> CPU domain is incorrect.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_gem_dmabuf.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> index 80bbe43a2e92..c7d734248ed0 100644
> --- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> +++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> @@ -299,6 +299,8 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
>  	drm_gem_private_object_init(dev, &obj->base, dma_buf->size);
>  	i915_gem_object_init(obj, &i915_gem_object_dmabuf_ops);
>  	obj->base.import_attach = attach;
> +	obj->base.read_domains = I915_GEM_DOMAIN_GTT;

I was a confused about the coherency guarantees of this _GTT.

But after chatting with Chris I am convinced that what comes to
coherency for other guests and sharing, this is it.

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

-Mika

> +	obj->base.write_domain = 0;
>  
>  	return &obj->base;
>  
> -- 
> 2.8.1
>
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