[Intel-gfx] [PATCH 0/6] Page faults to help user space debug

[Chris Wilson]

On Fri, Jun 28, 2013 at 03:23:31PM -0700, Ben Widawsky wrote:
> This series originated from the request from Paul, "can you enable page
> faults"?  After some though and discussion, we came up with 3 debug features to
> implement:

The issue lies in that the CS and EU units like to prefetch 128 bytes
and will cross page boundaries. Userspace is rather lax in providing the
extra page (or preventing the read past the end of its bo) and so
without adding a sentinel page behind every bo you quickly generate
false positives. (Unless you also run a fixed userspace).

If you are prepared to fix userspace, tweaking the kernel not to install
scratch pages everywhere is trivial.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre