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| author | Adrián Larumbe <adrian.larumbe@collabora.com> | 2026-05-22 19:51:59 +0100 |
|---|---|---|
| committer | Steven Price <steven.price@arm.com> | 2026-06-05 10:59:07 +0100 |
| commit | 12cf826bf1dd9275773cbef02c81ec1c67def7c3 (patch) | |
| tree | f775613775e9f71cfde96d1610cec1098656d23e /include/uapi/drm | |
| parent | d074bf042083d1a14995b3305b95bf1b4c96ae69 (diff) | |
| download | linux-next-12cf826bf1dd9275773cbef02c81ec1c67def7c3.tar.gz linux-next-12cf826bf1dd9275773cbef02c81ec1c67def7c3.zip | |
drm/panthor: Support sparse mappings
Allow UM to bind sparsely populated memory regions by cyclically mapping
virtual ranges over a kernel-allocated dummy BO. This alternative is
preferable to the old method of handling sparseness in the UMD, because it
relied on the creation of a buffer object to the same end, despite the fact
Vulkan sparse resources don't need to be backed by a driver BO.
The choice of backing sparsely-bound regions with a Panthor BO was made so
as to profit from the existing shrinker reclaim code. That way no special
treatment must be given to the dummy sparse BOs when reclaiming memory, as
would be the case if we had chosen a raw kernel page implementation.
A new dummy BO is allocated per open file context, because even though the
Vulkan spec mandates that writes into sparsely bound regions must be
discarded, our implementation is still a workaround over the fact Mali CSF
GPUs cannot support this behaviour on the hardware level, so writes still
make it into the backing BO. If we had a global one, then it could be a
venue for information leaks between file contexts, which should never
happen in DRM.
As a side note, care was put to adjust dummy BO offsets for sparse mappings
so that all addresses in the new VA are mapped aligned against it.
Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patch.msgid.link/20260522185206.2798288-6-adrian.larumbe@collabora.com
Signed-off-by: Steven Price <steven.price@arm.com>
Diffstat (limited to 'include/uapi/drm')
| -rw-r--r-- | include/uapi/drm/panthor_drm.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/include/uapi/drm/panthor_drm.h b/include/uapi/drm/panthor_drm.h index 14a93a4ef6ff..a2ff0f4ec691 100644 --- a/include/uapi/drm/panthor_drm.h +++ b/include/uapi/drm/panthor_drm.h @@ -615,6 +615,18 @@ enum drm_panthor_vm_bind_op_flags { DRM_PANTHOR_VM_BIND_OP_MAP_UNCACHED = 1 << 2, /** + * @DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE: Sparsely map a virtual memory range + * + * Only valid with DRM_PANTHOR_VM_BIND_OP_TYPE_MAP. + * + * When this flag is set, the whole vm_bind range is mapped over a dummy object in a cyclic + * fashion, and all GPU reads from addresses in the range return undefined values. This flag + * being set means drm_panthor_vm_bind_op::bo_offset and drm_panthor_vm_bind_op::bo_handle + * must both be set to 0. DRM_PANTHOR_VM_BIND_OP_MAP_NOEXEC must also be set. + */ + DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE = 1 << 3, + + /** * @DRM_PANTHOR_VM_BIND_OP_TYPE_MASK: Mask used to determine the type of operation. */ DRM_PANTHOR_VM_BIND_OP_TYPE_MASK = (int)(0xfu << 28), |