[PATCH v6 00/22] Add generic memory shrinker to VirtIO-GPU and Panfrost DRM drivers

Dmitry Osipenko
2022-05-26T23:54:14Z

Hello,

This patchset introduces memory shrinker for the VirtIO-GPU DRM driver
and adds memory purging and eviction support to VirtIO-GPU driver.

The new dma-buf locking convention is introduced here as well.

During OOM, the shrinker will release BOs that are marked as "not needed"
by userspace using the new madvise IOCTL, it will also evict idling BOs
to SWAP. 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.

The Panfrost driver is switched to use generic memory shrinker.

This patchset includes improvements and fixes for various things that
I found while was working on the shrinker.

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

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

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

Changelog:

v6: - Added new VirtIO-related fix patch that previously was sent separately
and didn't get much attention:

drm/gem: Properly annotate WW context on drm_gem_lock_reservations() error

- Added new patch that fixes mapping of imported dma-bufs for
Tegra DRM and other affected drivers. It's also handy to have it
for switching to the new dma-buf locking convention scheme:

drm/gem: Move mapping of imported dma-bufs to drm_gem_mmap_obj()

- Added new patch that fixes shrinker list corruption for stable Panfrost
driver:

drm/panfrost: Fix shrinker list corruption by madvise IOCTL

- Added new minor patch-fix for drm-shmem:

drm/shmem-helper: Add missing vunmap on error

- Added fixes tag to the "Put mapping ..." patch like was suggested by
Steven Price.

- Added new VirtIO-GPU driver improvement patch:

drm/virtio: Return proper error codes instead of -1

- Reworked shrinker patches like was suggested by Daniel Vetter:

- Introduced the new locking convention for dma-bufs. Tested on
VirtIO-GPU, Panfrost, Lima, Tegra and Intel selftests.

- Dropped separate purge() callback. Now single evict() does
everything.

- Dropped swap_in() callback from drm-shmem objects. DRM drivers
now could and should restore only the required mappings.

- Dropped dynamic counting of evictable pages. This simplifies
code in exchange to *potentially* burning more CPU time on OOM.

v5: - Added new for-stable patch "drm/panfrost: Put mapping instead of
shmem obj on panfrost_mmu_map_fault_addr() error" that corrects GEM's
refcounting in case of error.

- The drm_gem_shmem_v[un]map() now takes a separate vmap_lock for
imported GEMs to avoid recursive locking of DMA reservations.
This addresses v4 comment from Thomas Zimmermann about the potential
deadlocking of vmapping.

- Added ack from Thomas Zimmermann to "drm/shmem-helper: Correct
doc-comment of drm_gem_shmem_get_sg_table()" patch.

- Dropped explicit shmem states from the generic shrinker patch as
was requested by Thomas Zimmermann.

- Improved variable names and comments of the generic shrinker code.

- Extended drm_gem_shmem_print_info() with the shrinker-state info in
the "drm/virtio: Support memory shrinking" patch.

- Moved evict()/swap_in()/purge() callbacks from drm_gem_object_funcs
to drm_gem_shmem_object in the generic shrinker patch, for more
consistency.

- Corrected bisectability of the patches that was broken in v4
by accident.

- The virtio_gpu_plane_prepare_fb() now uses drm_gem_shmem_pin() instead
of drm_gem_shmem_set_unpurgeable_and_unevictable() and does it only for
shmem BOs in the "drm/virtio: Support memory shrinking" patch.

- Made more functions private to drm_gem_shmem_helper.c as was requested
by Thomas Zimmermann. This minimizes number of the public shmem helpers.

v4: - Corrected minor W=1 warnings reported by kernel test robot for v3.

- Renamed DRM_GEM_SHMEM_PAGES_STATE_ACTIVE/INACTIVE to PINNED/UNPINNED,
for more clarity.

v3: - Hardened shrinker's count() with usage of READ_ONCE() since we don't
use atomic type for counting and technically compiler is free to
re-fetch counter's variable.

- "Correct drm_gem_shmem_get_sg_table() error handling" now uses
PTR_ERR_OR_ZERO(), fixing typo that was made in v2.

- Removed obsoleted shrinker from the Panfrost driver, which I missed to
do in v2 by accident and Alyssa Rosenzweig managed to notice it.

- CCed stable kernels in all patches that make fixes, even the minor ones,
like was suggested by Emil Velikov and added his r-b to the patches.

- Added t-b from Steven Price to the Panfrost's shrinker patch.

- Corrected doc-comment of drm_gem_shmem_object.madv, like was suggested
by Steven Price. Comment now says that madv=1 means "object is purged"
instead of saying that value is unused.

- Added more doc-comments to the new shmem shrinker API.

- The "Improve DMA API usage for shmem BOs" patch got more improvements
by removing the obsoleted drm_dev_set_unique() quirk and its comment.

- Added patch that makes Virtio-GPU driver to use common dev_is_pci()
helper, which was suggested by Robin Murphy.

- Added new "drm/shmem-helper: Take GEM reservation lock instead of
drm_gem_shmem locks" patch, which was suggested by Daniel Vetter.

- Added new "drm/virtio: Simplify error handling of
virtio_gpu_object_create()" patch.

- Improved "Correct doc-comment of drm_gem_shmem_get_sg_table()" patch,
like was suggested by Daniel Vetter, by saying that function returns
ERR_PTR() and not errno.

- virtio_gpu_purge_object() is fenced properly now, turned out
virtio_gpu_notify() doesn't do fencing as I was supposing before.
Stress testing of memory eviction revealed that.

- Added new patch that corrects virtio_gpu_plane_cleanup_fb() to use
appropriate atomic plane state.

- SHMEM shrinker got eviction support.

- VirtIO-GPU driver now supports memory eviction. It's enabled for a
non-blob GEMs only, i.e. for VirGL. The blobs don't support dynamic
attaching/detaching of guest's memory, so it's not trivial to enable
them.

- Added patch that removes obsoleted drm_gem_shmem_purge()

- Added patch that makes drm_gem_shmem_get_pages() private.

- Added patch that fixes lockup on dma_resv_reserve_fences() error.

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 (22):
drm/gem: Properly annotate WW context on drm_gem_lock_reservations()
error
drm/gem: Move mapping of imported dma-bufs to drm_gem_mmap_obj()
drm/panfrost: Put mapping instead of shmem obj on
panfrost_mmu_map_fault_addr() error
drm/panfrost: Fix shrinker list corruption by madvise IOCTL
drm/virtio: Correct drm_gem_shmem_get_sg_table() error handling
drm/virtio: Check whether transferred 2D BO is shmem
drm/virtio: Unlock reservations on virtio_gpu_object_shmem_init()
error
drm/virtio: Unlock reservations on dma_resv_reserve_fences() error
drm/virtio: Use appropriate atomic state in
virtio_gpu_plane_cleanup_fb()
drm/shmem-helper: Add missing vunmap on error
drm/shmem-helper: Correct doc-comment of drm_gem_shmem_get_sg_table()
drm/virtio: Simplify error handling of virtio_gpu_object_create()
drm/virtio: Improve DMA API usage for shmem BOs
dma-buf: Introduce new locking convention
drm/shmem-helper: Don't use vmap_use_count for dma-bufs
drm/shmem-helper: Use reservation lock
drm/shmem-helper: Add generic memory shrinker
drm/gem: Add drm_gem_pin_unlocked()
drm/virtio: Support memory shrinking
drm/virtio: Use dev_is_pci()
drm/virtio: Return proper error codes instead of -1
drm/panfrost: Switch to generic memory shrinker

drivers/dma-buf/dma-buf.c | 270 ++++---
drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 6 +-
drivers/gpu/drm/drm_client.c | 4 +-
drivers/gpu/drm/drm_gem.c | 69 +-
drivers/gpu/drm/drm_gem_framebuffer_helper.c | 6 +-
drivers/gpu/drm/drm_gem_shmem_helper.c | 718 ++++++++++++++----
drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 10 +-
drivers/gpu/drm/lima/lima_gem.c | 8 +-
drivers/gpu/drm/lima/lima_sched.c | 4 +-
drivers/gpu/drm/panfrost/Makefile | 1 -
drivers/gpu/drm/panfrost/panfrost_device.h | 4 -
drivers/gpu/drm/panfrost/panfrost_drv.c | 26 +-
drivers/gpu/drm/panfrost/panfrost_gem.c | 33 +-
drivers/gpu/drm/panfrost/panfrost_gem.h | 9 -
.../gpu/drm/panfrost/panfrost_gem_shrinker.c | 122 ---
drivers/gpu/drm/panfrost/panfrost_job.c | 18 +-
drivers/gpu/drm/panfrost/panfrost_mmu.c | 21 +-
drivers/gpu/drm/panfrost/panfrost_perfcnt.c | 6 +-
drivers/gpu/drm/qxl/qxl_object.c | 17 +-
drivers/gpu/drm/qxl/qxl_prime.c | 4 +-
drivers/gpu/drm/tegra/gem.c | 4 +
drivers/gpu/drm/virtio/virtgpu_drv.c | 53 +-
drivers/gpu/drm/virtio/virtgpu_drv.h | 23 +-
drivers/gpu/drm/virtio/virtgpu_gem.c | 59 +-
drivers/gpu/drm/virtio/virtgpu_ioctl.c | 37 +
drivers/gpu/drm/virtio/virtgpu_kms.c | 16 +-
drivers/gpu/drm/virtio/virtgpu_object.c | 203 +++--
drivers/gpu/drm/virtio/virtgpu_plane.c | 28 +-
drivers/gpu/drm/virtio/virtgpu_vq.c | 61 +-
.../common/videobuf2/videobuf2-dma-contig.c | 11 +-
.../media/common/videobuf2/videobuf2-dma-sg.c | 11 +-
.../common/videobuf2/videobuf2-vmalloc.c | 11 +-
include/drm/drm_device.h | 4 +
include/drm/drm_gem.h | 6 +
include/drm/drm_gem_shmem_helper.h | 99 ++-
include/linux/dma-buf.h | 14 +-
include/uapi/drm/virtgpu_drm.h | 14 +
37 files changed, 1349 insertions(+), 661 deletions(-)
delete mode 100644 drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c

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2.35.3