Certain multi-GPU configurations (especially GFX12) may hit
data corruption when a DCC-compressed VRAM surface is shared across GPUs
using peer-to-peer (P2P) DMA transfers.
Such surfaces rely on device-local metadata and cannot be safely accessed
through a remote GPU’s page tables. Attempting to import a DCC-enabled
surface through P2P leads to incorrect rendering or GPU faults.
This change disables P2P for DCC-enabled VRAM buffers that are contiguous
and allocated on GFX12+ hardware. In these cases, the importer falls back
to the standard system-memory path, avoiding invalid access to compressed
surfaces.
Future work could consider optional migration (VRAM→System→VRAM) if a
performance regression is observed when `attach->peer2peer = false`.
Tested on:
- Dual RX 9700 XT (Navi4x) setup
- GNOME and Wayland compositor scenarios
- Confirmed no corruption after disabling P2P under these conditions
v2: Remove check TTM_PL_VRAM & TTM_PL_FLAG_CONTIGUOUS.
v3: simplify for upsteam and fix ip version check (Alex)
Suggested-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Vitaly Prosyak <vitaly.prosyak@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
9dff2bb709