[PATCH v2 0/8] Add memory shrinker to VirtIO-GPU DRM driver

[Dmitry Osipenko]

Hello,

This patchset introduces memory shrinker for the VirtIO-GPU DRM driver.
During OOM, the shrinker will release BOs that are marked as "not needed"
by userspace using the new madvise IOCTL. The userspace in this case is
the Mesa VirGL driver, it will mark the cached BOs as "not needed",
allowing kernel driver to release memory of the cached shmem BOs on lowmem
situations, preventing OOM kills.

This patchset includes couple fixes for problems of VirtIO-GPU driver that
I found while was working on the shrinker, it also includes prerequisite
DMA API usage improvement needed by the shrinker.

The Mesa and IGT patches will be kept on hold until this kernel series
will be approved and applied.

This patchset was tested using Qemu and crosvm, including both cases of
IOMMU off/on.

Note that this patchset only enables initial shrinking of the guest memory,
shrinking of the host memory is unsupported yet.

Mesa: https://gitlab.freedesktop.org/digetx/mesa/-/commits/virgl-madvise
IGT:  https://gitlab.freedesktop.org/digetx/igt-gpu-tools/-/tree/virtio-madvise

Changelog:

v2: - Improved shrinker by using a more fine-grained locking to reduce
      contention during scan of objects and dropped locking from the
      'counting' callback by tracking count of shrinkable pages. This
      was suggested by Rob Clark in the comment to v1.

    - Factored out common shrinker code into drm_gem_shmem_helper.c
      and switched Panfrost driver to use the new common memory shrinker.
      This was proposed by Thomas Zimmermann in his prototype series that
      he shared with us in the comment to v1. Note that I only compile-tested
      the Panfrost driver.

    - Shrinker now takes object_name_lock during scan to prevent racing
      with dma-buf exporting.

    - Shrinker now takes vmap_lock during scan to prevent racing with shmem
      vmap/unmap code.

    - Added "Correct doc-comment of drm_gem_shmem_get_sg_table()" patch,
      which I sent out previously as a standalone change, since the
      drm_gem_shmem_helper.c is now touched by this patchset anyways and
      it doesn't hurt to group all the patches together.

Dmitry Osipenko (8):
  drm/virtio: Correct drm_gem_shmem_get_sg_table() error handling
  drm/virtio: Check whether transferred 2D BO is shmem
  drm/virtio: Unlock GEM reservations in error code path
  drm/virtio: Improve DMA API usage for shmem BOs
  drm/shmem-helper: Correct doc-comment of drm_gem_shmem_get_sg_table()
  drm/shmem-helper: Add generic memory shrinker
  drm/virtio: Support memory shrinking
  drm/panfrost: Switch to generic memory shrinker

 drivers/gpu/drm/drm_gem_shmem_helper.c     | 196 ++++++++++++++++++++-
 drivers/gpu/drm/panfrost/Makefile          |   1 -
 drivers/gpu/drm/panfrost/panfrost_device.h |   4 -
 drivers/gpu/drm/panfrost/panfrost_drv.c    |  19 +-
 drivers/gpu/drm/panfrost/panfrost_gem.c    |  27 +--
 drivers/gpu/drm/panfrost/panfrost_gem.h    |   9 -
 drivers/gpu/drm/panfrost/panfrost_job.c    |  22 ++-
 drivers/gpu/drm/virtio/virtgpu_drv.c       |  22 ++-
 drivers/gpu/drm/virtio/virtgpu_drv.h       |  26 ++-
 drivers/gpu/drm/virtio/virtgpu_gem.c       |  96 ++++++++++
 drivers/gpu/drm/virtio/virtgpu_ioctl.c     |  37 ++++
 drivers/gpu/drm/virtio/virtgpu_kms.c       |  17 +-
 drivers/gpu/drm/virtio/virtgpu_object.c    |  78 ++++----
 drivers/gpu/drm/virtio/virtgpu_plane.c     |  17 +-
 drivers/gpu/drm/virtio/virtgpu_vq.c        |  30 +++-
 include/drm/drm_device.h                   |   4 +
 include/drm/drm_gem.h                      |  11 ++
 include/drm/drm_gem_shmem_helper.h         |  25 +++
 include/uapi/drm/virtgpu_drm.h             |  14 ++
 19 files changed, 544 insertions(+), 111 deletions(-)

-- 
2.35.1