[PATCH v5 0/4] Support for creating/using Stolen memory backed objects

[ankitprasad.r.sharma@intel.com]

From: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>

This patch series adds support for creating/using Stolen memory backed
objects.

Despite being a unified memory architecture (UMA) some bits of memory
are more equal than others. In particular we have the thorny issue of
stolen memory, memory stolen from the system by the BIOS and reserved
for igfx use. Stolen memory is required for some functions of the GPU
and display engine, but in general it goes wasted. Whilst we cannot
return it back to the system, we need to find some other method for
utilising it. As we do not support direct access to the physical address
in the stolen region, it behaves like a different class of memory,
closer in kin to local GPU memory. This strongly suggests that we need a
placement model like TTM if we are to fully utilize these discrete
chunks of differing memory.

To add support for creating Stolen memory backed objects, we extend the
drm_i915_gem_create structure, by adding a new flag through which user
can specify the preference to allocate the object from stolen memory,
which if set, an attempt will be made to allocate the object from stolen
memory subject to the availability of free space in the stolen region.

This patch series adds support for clearing buffer objects via CPU/GTT.
This is particularly useful for clearing out the memory from stolen
region, but can also be used for other shmem allocated objects. Currently
being used for buffers allocated in the stolen region. Also adding support
for stealing purgable stolen pages, if we run out of stolen memory when
trying to allocate an object.

v2: Added support for read/write from/to objects not backed by
shmem using the pread/pwrite interface.
Also extended the current get_aperture ioctl to retrieve the
total and available size of the stolen region

v3: Removed the extended get_aperture ioctl patch 5 (to be submitted as
part of other patch series), addressed comments by Chris about pread/pwrite
for non shmem backed objects

v4: Rebased to the latest drm-intel-nightly

v5: Addressed comments, replaced patch 1/4 "Clearing buffers via blitter
engine" by "Clearing buffers via CPU/GTT"

This can be verified using IGT tests: igt/gem_stolen, igt/gem_create

Ankitprasad Sharma (3):
  drm/i915: Clearing buffer objects via CPU/GTT
  drm/i915: Support for creating Stolen memory backed objects
  drm/i915: Support for pread/pwrite from/to non shmem backed objects

Chris Wilson (1):
  drm/i915: Add support for stealing purgable stolen pages

 drivers/gpu/drm/i915/i915_dma.c        |   3 +
 drivers/gpu/drm/i915/i915_drv.h        |   1 +
 drivers/gpu/drm/i915/i915_gem.c        | 205 +++++++++++++++++++++++++++++----
 drivers/gpu/drm/i915/i915_gem_stolen.c | 122 ++++++++++++++++++--
 include/uapi/drm/i915_drm.h            |  15 +++
 5 files changed, 314 insertions(+), 32 deletions(-)

-- 
1.9.1

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