[Mesa-stable] [Mesa-dev] [PATCH] i965: Fix buffer overruns in MSAA MCS buffer clearing.

[Kenneth Graunke]

On 04/15/2014 05:16 PM, Ian Romanick wrote:
> On 04/15/2014 03:50 PM, Kenneth Graunke wrote:
>> On 04/15/2014 10:08 AM, Mike Stroyan wrote:
>>> I would go farther than requiring the returned bo->size to be covered by
>>> backing pages.
>>> There really should be backing pages for every page mapped by
>>> drm_intel_gem_bo_map.
>>> No mapped addresses should be affecting memory outside of an object's
>>> backing pages.
>>>
>>> If tiling can result in access to unallocated memory it might even lead
>>> to corruption of data in pages
>>> used by different processes.  That would break GL_ARB_robustness
>>> requirements.
>>
>> It shouldn't, now that proper PPGTT support has landed in the kernel -
>> only data belonging to a single process is mapped into its address
>> space.  So, a process can accidentally read or trash other portions of
>> its own memory, but never any other memory.  This seems acceptable, as
>> it's how things work with normal CPU programs.
> 
> It is fine... for now.  GL_ARB_robust_buffer_access makes stronger
> guarantees about out-of-buffer accesses.  Reads outside a buffer (e.g.,
> accessing too large an array element for an array contained in a UBO)
> can only return data from elsewhere in the buffer or zero.  WebGL
> implementers really want this.
> 
> I don't think that's relevant here because the fences only apply to CPU
> access, yeah?

Right.  This shouldn't affect that.


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