On 03/25/2015 01:29 PM, Chris Wilson wrote:
Our GPUs impose certain requirements upon buffers that depend upon how
exactly they are used. Typically this is expressed as that they require
a larger surface than would be naively computed by pitch * height.
Normally such requirements are hidden away in the userspace driver, but
when we accept pointers from strangers and later impose extra conditions
on them, the original client allocator has no idea about the
monstrosities in the GPU and we require the userspace driver to inform
the kernel how many padding pages are required beyond the client
allocation.
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
---
Tvrtko is working on an igt to exercise this feature. The original
request basically stems from trying to mix client allocations (userptr)
and tiling. But I see it as a nice extension of our lazy_fencing code to
reduce buffer sizes for tiled allocations (as we then do not need to
allocate the entire last tilerow) and for relaxing restrictions on
foriegn buffers like DRI3.
---
(Original request was actually about sampler overfetch in various
texture modes.)
We talked about per-process (or so) scratch pages before. I looked now
but I see at the moment even PPGTT shares the same scratch page so
presumably that means someone has thought about security and decided
that is fine?
Otherwise looks good to me.
Regards,
Tvrtko
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