drm/amdgpu: Add debug bit for userptr usage

In VM debug mode, it is desirable to notify the application
to correct the freeing sequence by unmapping the memory before
destroying the userptr in the old userptr path. Add a bitmask
to decide whether to send gpu vm fault to the applition.

Signed-off-by: Shane Xiao <shane.xiao@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: AMD-ShaneXiao

drivers/gpu/drm/amd/amdgpu/amdgpu.h

@@ -1281,6 +1281,7 @@ struct amdgpu_device {
 	bool                            debug_enable_ras_aca;
 	bool                            debug_exp_resets;
 	bool                            debug_disable_gpu_ring_reset;
+	bool                            debug_vm_userptr;
 
 	/* Protection for the following isolation structure */
 	struct mutex                    enforce_isolation_mutex;

drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c

@@ -143,6 +143,7 @@ enum AMDGPU_DEBUG_MASK {
 	AMDGPU_DEBUG_ENABLE_EXP_RESETS = BIT(5),
 	AMDGPU_DEBUG_DISABLE_GPU_RING_RESET = BIT(6),
 	AMDGPU_DEBUG_SMU_POOL = BIT(7),
+	AMDGPU_DEBUG_VM_USERPTR = BIT(8),
 };
 
 unsigned int amdgpu_vram_limit = UINT_MAX;
@@ -2273,6 +2274,10 @@ static void amdgpu_init_debug_options(struct amdgpu_device *adev)
 		pr_info("debug: use vram for smu pool\n");
 		adev->pm.smu_debug_mask |= SMU_DEBUG_POOL_USE_VRAM;
 	}
+	if (amdgpu_debug_mask & AMDGPU_DEBUG_VM_USERPTR) {
+		pr_info("debug: VM mode debug for userptr is enabled\n");
+		adev->debug_vm_userptr = true;
+	}
 }
 
 static unsigned long amdgpu_fix_asic_type(struct pci_dev *pdev, unsigned long flags)