Adrián Larumbe 12cf826bf1 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>
2026-06-05 10:59:07 +01:00
2026-01-26 19:07:09 -08:00
2022-09-28 09:02:20 +02:00
2025-02-19 14:53:27 -07:00
2026-05-28 09:58:36 +02:00
2026-05-24 13:48:06 -07:00

Linux kernel
============

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