[webkit-dev] Feature announcement: WebCL

Oliver Hunt oliver at apple.com
Wed May 1 17:41:19 PDT 2013

On May 1, 2013, at 5:29 PM, Antonio Gomes <tonikitoo at webkit.org> wrote:
> - 4.2 Cross-Origin Information Leakage
> WebCL's position is that this be handled by the same mechanism as used for WebGL, ie https://www.khronos.org/registry/webgl/specs/latest/#4.2 . A bug will be filed to request update of wording in the working draft.

> - 4.3 Out-of-Range Memory Access
> The validator will perform static analysis on WebCL kernels to determine violations of WebCL kernel behavior and language restrictions. The results from the analysis will also be used to determine any necessary instrumentation to bring the WebCL kernels in compliance with security and syntactic requirements of the WebCL API.  The RFQ for the WebCL Validator located at https://cvs.khronos.org/wiki/index.php/WebCL_Validator provides information on the approach recommended by the WebCL working group. 

How do you statically verify the all memory accesses are within bounds without limiting a WebCL kernel to the functionality already offered by shaders in WebGL?
> - 4.6 Prevention of potential denial of service (DoS) from long running kernels:
> This is addressed by the OpenCL CL_CONTEXT_TERMINATE extension. In http://www.khronos.org/registry/cl/specs/opencl-1.2-extensions.pdf , please refer to section "9.16 Terminating OpenCL contexts".
I haven't seen any real evidence of widespread support for responsive termination in WebGL shaders yet, and given that the same hardware is involved when you want GPU backed WebCL I don't see how much this will help.

> It is chicken-egg problem: without Browser vendors commitment to WebCL, the  motivation for hardware vendors to implement, for example, OpenCL 1.2 "Memory Initialization" and "Context termination" extensions, required by WebCL, is not as strong.

The extensions mentioned above are required by WebGL shaders, and WebGL has been around for a lot longer (and has even more stringent requirements than WebCL) - are there any GPUs that support the WebGL restrictions natively?


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