[PATCH 2/2] amd/amdkfd: Trigger segfault for early userptr unmmapping

[Shane Xiao]

If applications unmap the memory before destroying the userptr, it needs
trigger a segfault to notify user space to correct the free sequence in
VM debug mode.

v2: Send GPU access fault to user space

Signed-off-by: Shane Xiao <shane.xiao at amd.com>
---
 .../gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c  | 14 +++++++++++++
 drivers/gpu/drm/amd/amdkfd/kfd_events.c       | 20 +++++++++++++++++++
 drivers/gpu/drm/amd/amdkfd/kfd_priv.h         |  3 +++
 3 files changed, 37 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
index d2ec4130a316..876e9df34adf 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
@@ -2496,6 +2496,7 @@ static int update_invalid_user_pages(struct amdkfd_process_info *process_info,
 	struct ttm_operation_ctx ctx = { false, false };
 	uint32_t invalid;
 	int ret = 0;
+	uint64_t userptr = 0;
 
 	mutex_lock(&process_info->notifier_lock);
 
@@ -2559,6 +2560,19 @@ static int update_invalid_user_pages(struct amdkfd_process_info *process_info,
 			if (ret != -EFAULT)
 				return ret;
 
+			/* If applications unmap memory before destroying the userptr
+			 * from the KFD, trigger a segmentation fault in VM debug mode.
+			 */
+			if (amdgpu_ttm_adev(bo->tbo.bdev)->debug_vm_userptr) {
+				amdgpu_ttm_tt_get_userptr(&bo->tbo, userptr);
+				pr_err("User space unmap memory before destroying a userptr that refers to it\n");
+				pr_err("The unmap userptr address is 0x%llx\n", userptr);
+
+				// Send GPU VM fault to user space
+				kfd_signal_vm_fault_event_with_userptr(kfd_lookup_process_by_pid(process_info->pid),
+						amdgpu_ttm_adev(bo->tbo.bdev)->kfd.dev, userptr);
+			}
+
 			ret = 0;
 		}
 
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_events.c b/drivers/gpu/drm/amd/amdkfd/kfd_events.c
index fecdb6794075..89943d2146a4 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_events.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_events.c
@@ -1177,6 +1177,26 @@ void kfd_signal_hw_exception_event(u32 pasid)
 	kfd_unref_process(p);
 }
 
+void kfd_signal_vm_fault_event_with_userptr(struct kfd_process *p,
+		struct kfd_dev *dev , uint64_t userptr)
+{
+	struct kfd_process_device *pdd;
+	struct kfd_hsa_memory_exception_data exception_data;
+	int i;
+
+	memset(&exception_data, 0, sizeof(exception_data));
+	exception_data.va = userptr;
+	exception_data.failure.NotPresent = 1;
+
+	// Send VM seg fault to all kfd process device
+	for (i = 0; i < p->n_pdds; i++) {
+		pdd = p->pdds[i];
+		exception_data.gpu_id = pdd->user_gpu_id;
+		kfd_evict_process_device(pdd);
+		kfd_signal_vm_fault_event(pdd, NULL, &exception_data);
+	}
+}
+
 void kfd_signal_vm_fault_event(struct kfd_process_device *pdd,
 				struct kfd_vm_fault_info *info,
 				struct kfd_hsa_memory_exception_data *data)
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
index f6aedf69c644..34f47dc1cbbd 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
@@ -1507,6 +1507,9 @@ int kfd_event_create(struct file *devkfd, struct kfd_process *p,
 int kfd_get_num_events(struct kfd_process *p);
 int kfd_event_destroy(struct kfd_process *p, uint32_t event_id);
 
+void kfd_signal_vm_fault_event_with_userptr(struct kfd_process *p,
+				struct kfd_dev *dev , uint64_t userptr);
+
 void kfd_signal_vm_fault_event(struct kfd_process_device *pdd,
 				struct kfd_vm_fault_info *info,
 				struct kfd_hsa_memory_exception_data *data);
-- 
2.25.1