[Mesa-dev] [PATCH 1/6] radeonsi: allow DMABUF exports for local buffers

[Nicolai Hähnle]

On 05.12.2017 20:05, Marek Olšák wrote:
> From: Marek Olšák <marek.olsak at amd.com>
> 
> Cc: 17.3 <mesa-stable at lists.freedesktop.org>
> ---
>   src/gallium/drivers/radeon/r600_texture.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/src/gallium/drivers/radeon/r600_texture.c b/src/gallium/drivers/radeon/r600_texture.c
> index 2aa47b5..07f7c33 100644
> --- a/src/gallium/drivers/radeon/r600_texture.c
> +++ b/src/gallium/drivers/radeon/r600_texture.c
> @@ -739,22 +739,26 @@ static boolean r600_texture_get_handle(struct pipe_screen* screen,
>   			stride = rtex->surface.u.gfx9.surf_pitch *
>   				 rtex->surface.bpe;
>   			slice_size = rtex->surface.u.gfx9.surf_slice_size;
>   		} else {
>   			offset = rtex->surface.u.legacy.level[0].offset;
>   			stride = rtex->surface.u.legacy.level[0].nblk_x *
>   				 rtex->surface.bpe;
>   			slice_size = (uint64_t)rtex->surface.u.legacy.level[0].slice_size_dw * 4;
>   		}
>   	} else {
> +		/* Buffer exports are for the OpenCL interop. */
>   		/* Move a suballocated buffer into a non-suballocated allocation. */
> -		if (sscreen->ws->buffer_is_suballocated(res->buf)) {
> +		if (sscreen->ws->buffer_is_suballocated(res->buf) ||
> +		    /* A DMABUF export always fails if the BO is local. */
> +		    (rtex->resource.flags & RADEON_FLAG_NO_INTERPROCESS_SHARING &&
> +		     whandle->type != DRM_API_HANDLE_TYPE_KMS)) {

I still don't think this is right. Or at least, it's bound to blow up in 
our faces at some point. Though I think we may have talked past each 
other, apologies that I haven't made myself clear.

The issues I have in mind are scenarios like this:

1. Buffer allocated in OpenGL.
2. Buffer exported as KMS handle for importing to OpenCL in the same 
process.
3. Buffer exported as an FD <-- at this point, the OpenGL and OpenCL 
buffers go out of sync because OpenGL re-allocates the buffer but OpenCL 
isn't informed.

Or:

1. Buffer allocated in OpenGL.
2. Buffer exported as KMS handle for importing to OpenCL in the same 
process.
3. Buffer attempted to be exported as an FD from OpenCL <-- fails 
because the buffer is local (has NO_INTERPROCESS_SHARING), and people 
will be utterly clueless as to what's going on.

FWIW, I think the patch is good if you drop the whandle->type check so 
that we re-allocate unconditionally.

Cheers,
Nicolai


>   			assert(!res->b.is_shared);
>   
>   			/* Allocate a new buffer with PIPE_BIND_SHARED. */
>   			struct pipe_resource templ = res->b.b;
>   			templ.bind |= PIPE_BIND_SHARED;
>   
>   			struct pipe_resource *newb =
>   				screen->resource_create(screen, &templ);
>   			if (!newb)
>   				return false;
> 


-- 
Lerne, wie die Welt wirklich ist,
Aber vergiss niemals, wie sie sein sollte.