Background
==========
When a GPU shader hits a hardware exception (s_trap 1), the first-level
CWSR trap handler reads TMA slots 0 and 1. If slot 0 contains a non-zero
address, the handler chains to the user-installed second-level TBA and
TMA. This is the mechanism used by RADV/Valve for GPU shader debugging.
KFD already provides this for compute workloads via kfd_process. Render-
node file descriptors had no equivalent.
Design
======
- One global TBA BO (adev->trap_info->isa_bo) holds the shared ISA
binary and is mapped into every GPUVM at AMDGPU_VA_RESERVED_TRAP_START.
The ISA binary is identical across VMs for the same hardware generation,
so one device-level allocation is sufficient.
- One per-VM TMA BO is allocated at vm_init and mapped at
AMDGPU_VA_RESERVED_TRAP_START + 0x1800. The 0x1800 offset matches
KFD_CWSR_TMA_OFFSET so both KFD and render-node VMs share the same
per-VM buffer layout.
- SQ_SHADER_TBA/TMA registers are programmed for kernel-managed VMIDs
from each gfxhub's setup_vmid_config() path. User-queue VMIDs receive
their register state from MES/KIQ at queue creation.
- SET_L2_TRAP is a per-VM operation exposed via the existing VM ioctl.
All shader waves executing under that VMID — whether submitted through
user queues or kernel queues — see the same second-level handler.
- For user queues, SET/CLEAR evicts all queues and flushes the GPU TLB
before writing the descriptor. For kernel queues, the VM is drained
via amdgpu_vm_wait_idle() before eviction and the write.
- Both TBA and TMA BOs must be allocated with VM_ALWAYS_VALID. The GPU
jumps to TBA automatically on exception without any software job
submission, so the kernel cannot add them to a job's used-buffer list.
Only compilation tested.
Srinivasan Shanmugam (4):
drm/amdgpu: Add second-level trap handler infrastructure
drm/amdgpu: Make first-level trap state GPUVM-owned
drm/amdgpu: Program trap TBA/TMA for kernel-managed VMIDs
drm/amdgpu/uapi: Add SET/CLEAR L2 TRAP to VM ioctl
drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 1 -
drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c | 8 +-
drivers/gpu/drm/amd/amdgpu/amdgpu_trap.c | 288 ++++++++++++++------
drivers/gpu/drm/amd/amdgpu/amdgpu_trap.h | 73 ++++-
drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c | 22 +-
drivers/gpu/drm/amd/amdgpu/amdgpu_userq.h | 1 +
drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 44 +++
drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h | 3 +
drivers/gpu/drm/amd/amdgpu/gfxhub_v11_5_0.c | 35 +++
drivers/gpu/drm/amd/amdgpu/gfxhub_v12_0.c | 35 +++
drivers/gpu/drm/amd/amdgpu/gfxhub_v12_1.c | 39 +++
drivers/gpu/drm/amd/amdgpu/gfxhub_v2_0.c | 35 +++
drivers/gpu/drm/amd/amdgpu/gfxhub_v3_0.c | 35 +++
include/uapi/drm/amdgpu_drm.h | 114 ++++++--
14 files changed, 613 insertions(+), 120 deletions(-)
--
2.34.1
