On 6/30/2026 10:26 PM, Matthew Brost wrote:
On Tue, Jun 30, 2026 at 06:21:22PM +0800, Honglei Huang wrote:
The intent of this series is to make drm_gpusvm more flexible and give
drivers more freedom over how they assemble the MM related and device
side operations. It implements the direction Matt suggested in [1]:
Mirror MR in gitlab: [4]
- Move struct drm_gpusvm_pages out of struct drm_gpusvm_range.
- Embed a struct drm_device in struct drm_gpusvm_pages and drive all
DMA through it.
- Drop struct drm_device from struct drm_gpusvm.
- Have the driver's range structure embed one or more struct
drm_gpusvm_pages in addition to struct drm_gpusvm_range.
- Drop the range-based helpers (drm_gpusvm_range_pages_valid,
drm_gpusvm_range_get_pages, drm_gpusvm_range_unmap_pages) and update
drivers to use the drm_gpusvm_pages helpers instead.
In essence the series does only two abstractions, plus the xe
adaptation that follows from them:
- range vs pages: split drm_gpusvm_range (MM / VA range state) from
drm_gpusvm_pages (device physical related), so the two sides can
have independent lifetimes and ownership.
- drm_gpusvm vs drm_device: make drm_gpusvm pure MM level and push
the device side down onto drm_gpusvm_pages, which is where DMA
actually happens.
- xe is updated to fit the modifications, no functional change
intended.
V10:
Fix two issues found by the AI review:
- patch 1: fix a KCSAN data race in xe_svm_alloc_vram(): read
range->base.flags.__flags with READ_ONCE() and assert on a local
copy, pairing with the WRITE_ONCE() in
drm_gpusvm_range_set_unmapped().
- patch 3: remove the DMA unmap in xe_svm_fini(): since
drm_gpusvm_range_remove() no longer unmaps synchronously, explicitly
drm_gpusvm_unmap_pages() all remaining ranges before
drm_gpusvm_fini().
V9:
- patch 3: fix the build with CONFIG_DRM_XE_GPUSVM disabled: move
pages out of the nested base struct in the stub xe_svm_range and
route has_dma_mapping through range->pages. No functional change.
V8:
- patch 4: add reviewed-by for Matt's review.
V7:
- patch 1: split MM state flags: the AI review found a KCSAN / memory
model cleanliness issue. Address it for consistency with
drm_gpusvm_pages_flags, set the range flags with WRITE_ONCE() on
__flags and read them with READ_ONCE().
V6:
- The AI review flagged a potential DMA free issue: the DMA unmap
step was moved into the range_free callback, but on the invalidate
path a range can be removed from the MMU interval tree while its DMA
mappings are still live, so a concurrent unmap event can miss it.
- patch 3: have xe_svm_range embed one drm_gpusvm_pages: explicitly
call drm_gpusvm_unmap_pages() before drm_gpusvm_range_remove() in the
garbage collector, so a range is never off the tree while still DMA
mapped, and document this caller contract in drm_gpusvm_range_remove()
kernel-doc.
- patch 4: move struct drm_gpusvm_pages out: document the
unmap before remove contract in the garbage collector example and
note that range_free()'s drm_gpusvm_free_pages() as a final fallback.
- patch 1: split MM state flags: return -EACCES directly.
- Fold in the pre existing IOVA/DMA unmap fixes the AI review found
previously sent separately: the uninitialized dma_addr[0].dir on
the get_pages() error path, the whole reservation IOVA free for
mixed ranges, and the device mapping leak on the get_pages() error
path. [6]
V5:
- add reviewed-by in patches 1, 2, 3, 5 for Matt's review.
V4:
- drm_gpusvm_init_pages(): memset() the pages to zero before recording
the owning drm_device.
- DOC: overview: recommend a zeroing allocator: kcalloc() for the
N:1 pages array.
- Rebased onto the latest drm-xe.
- The AI review of this series flagged two preexisting issues in the
IOVA unmap path that are not introduced by this series; they are
fixed in a separate series [5].
V3:
- Fix a kernel-doc/Sphinx warning from the kernel test robot: use
".. code-block:: c" for the drm_gpusvm_pages example in DOC: overview.
- drm_gpusvm_range_set_unmapped(): use WRITE_ONCE() on the whole
pages[i].flags.__flags word to pair with the lockless READ_ONCE()
readers and avoid a data race.
- xe_userptr_setup(): call drm_gpusvm_init_pages() before
mmu_interval_notifier_insert() to avoid exposing uninitialized
pages.drm to invalidation callbacks.
- Fix per commit build of the set_unmapped() pages.
V2:
- Followed in Matt's v0 review fixups [2]:
- keep unmapped flag in pages structures.
- add pages_count to drm_gpusvm_range_set_unmapped() to set the pages
unmapped flag, so the framework can check unmapped status in
drm_gpusvm_get_pages().
- Add drm_gpusvm_init_pages to init the drm_device and sequence number.
- Remove drm_device from drm_gpusvm_get_pages() parameters.
- Reworked the DOC: overview and usage examples to describe the new
model: struct drm_gpusvm_pages, the 1:1 / N:1 driver layouts, and
examples that operate on a driver embedded pages object by the
drm_gpusvm_pages helpers and etc.
- remove WARN_ON_ONCE in __drm_gpusvm_unmap_pages.
- Dropped RFC.
Follow-up (not in this series):
- modify drm_gpusvm_get_pages() to support one time hmm range fault
and multi drm device dma mapping.
- Add no dma device support for drm_gpusvm_get_pages().
tests:
AMDGPU:
based on amdgpu adaptation patch in [3], but still SVM:DRM = 1:1,
1:n is on going needs many modifications and testings.
Tested on gfx943 (MI300X) and gfx906 (MI60) with XNACK on/off:
- KFD test: 95%+ passed.
- ROCR test: all passed.
- HIP catch test: gfx943 (MI300X): 99% passed.
gfx906 (MI60): 99% passed.
INTEL XE:
CI tests passed in rev5 tests.[7]
CI full is in flight, but it seems likely to pass. Once it completes, we
can merge this; we just need to decide which branch to use.
The series does not apply cleanly to drm-misc-next because it depends on
changes in drm-xe-next that have not yet been merged into drm-misc-next.
It does apply cleanly to drm-xe-next, though.
If we merge the patches in drm-xe-next and pick them up via a rebase in
the AMD trees, that works. Alternatively, we can ask the drm-misc-next
maintainers to rebase and apply them there. Either option works for me.
Thanks a lot, Matt, for the guidance and the reviews in this series.
For the merge, happy to rebase onto whatever base/tag decided, just
let me know.
And will work on the follow up works.
Regards,
Honglei
Matt
links:
[1]
https://lore.kernel.org/amd-gfx/acRgr7QwdULsn6G2@gsse-cloud1/#:~:text=I%20think%20roughly,drm_gpusvm_pages%0A%20%20helpers%20instead.
[2]
https://gitlab.freedesktop.org/mbrost/xe-kernel-driver-svn-perf-6-15-2025/-/commit/623f6a50c037d9e44f6c9fbe6859a0ba7ad50177
[3]
https://lore.kernel.org/amd-gfx/[email protected]/
[4] https://gitlab.freedesktop.org/drm/xe/kernel/-/merge_requests/360
[5] https://lore.kernel.org/all/[email protected]/
[6] https://lore.kernel.org/all/[email protected]/
[7] https://patchwork.freedesktop.org/series/169384/#rev5
Honglei Huang (5):
drm/gpusvm: split MM state flags out of drm_gpusvm_pages_flags
drm/gpusvm: embed struct drm_device into drm_gpusvm_pages
drm/xe: have xe_svm_range embed one drm_gpusvm_pages
drm/gpusvm: move struct drm_gpusvm_pages out of struct
drm_gpusvm_range
drm/gpusvm: let the drm_gpusvm core context purely MM level
drivers/gpu/drm/drm_gpusvm.c | 243 +++++++++++++++++++-------------
drivers/gpu/drm/xe/xe_pt.c | 2 +-
drivers/gpu/drm/xe/xe_svm.c | 66 +++++++--
drivers/gpu/drm/xe/xe_svm.h | 14 +-
drivers/gpu/drm/xe/xe_userptr.c | 5 +-
include/drm/drm_gpusvm.h | 67 ++++++---
6 files changed, 255 insertions(+), 142 deletions(-)
--
2.34.1
