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H A D | kfd_flat_memory.c | 96c211f1 Wed Jul 12 15:53:44 CDT 2023 Jay Cornwall <jay.cornwall@amd.com> drm/amdkfd: Relocate TBA/TMA to opposite side of VM hole
The TBA and TMA, along with an unused IB allocation, reside at low addresses in the VM address space. A stray VM fault which hits these pages must be serviced by making their page table entries invalid. The scheduler depends upon these pages being resident and fails, preventing a debugger from inspecting the failure state.
By relocating these pages above 47 bits in the VM address space they can only be reached when bits [63:48] are set to 1. This makes it much less likely for a misbehaving program to generate accesses to them. The current placement at VA (PAGE_SIZE*2) is readily hit by a NULL access with a small offset.
Signed-off-by: Jay Cornwall <jay.cornwall@amd.com> Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
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