drm/amdkfd: Prevent user space using both svm and kfd api to register same user buffer

When xnack is on user space can use svm page restore to set a vm range without
setup it first, then use regular api to register. Currently kfd api and svm are
not interoperable. We already have check on that, but for user buffer the mapping
address is not same as buffer cpu virtual address. Add checking on that to
avoid error propagate to hmm.

Signed-off-by: Xiaogang Chen <xiaogang.chen@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_chardev.c

@@ -1065,6 +1065,20 @@ static int kfd_ioctl_alloc_memory_of_gpu(struct file *filep,
 		mutex_unlock(&p->svms.lock);
 		return -EADDRINUSE;
 	}
+
+	/* When register user buffer check if it has been registered by svm by
+	 * buffer cpu virtual address.
+	 */
+	if ((flags & KFD_IOC_ALLOC_MEM_FLAGS_USERPTR) &&
+	    interval_tree_iter_first(&p->svms.objects,
+				     args->mmap_offset >> PAGE_SHIFT,
+				     (args->mmap_offset  + args->size - 1) >> PAGE_SHIFT)) {
+		pr_err("User Buffer Address: 0x%llx already allocated by SVM\n",
+			args->mmap_offset);
+		mutex_unlock(&p->svms.lock);
+		return -EADDRINUSE;
+	}
+
 	mutex_unlock(&p->svms.lock);
 #endif
 	mutex_lock(&p->mutex);