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998d678141
For gfxV9, due to a hardware bug ("based on the comments in the code
here [1]"), the control stack of a user-mode compute queue must be
allocated immediately after the page boundary of its regular MQD buffer.
To handle this, we allocate an enlarged MQD buffer where the first page
is used as the MQD and the remaining pages store the control stack.
Although these regions share the same BO, they require different memory
types: the MQD must be UC (uncached), while the control stack must be
NC (non-coherent), matching the behavior when the control stack is
allocated in user space.
This logic works correctly on systems where the CPU page size matches
the GPU page size (4K). However, the current implementation aligns both
the MQD and the control stack to the CPU PAGE_SIZE. On systems with a
larger CPU page size, the entire first CPU page is marked UC—even though
that page may contain multiple GPU pages. The GPU treats the second 4K
GPU page inside that CPU page as part of the control stack, but it is
incorrectly mapped as UC.
This patch fixes the issue by aligning both the MQD and control stack
sizes to the GPU page size (4K). The first 4K page is correctly marked
as UC for the MQD, and the remaining GPU pages are marked NC for the
control stack. This ensures proper memory type assignment on systems
with larger CPU page sizes.
[1]: https://elixir.bootlin.com/linux/v6.18/source/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c#L118
Acked-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Donet Tom <donettom@linux.ibm.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
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