device_arena_alloc
void *device_arena_alloc(size_t size, int vm_flag);
cvaddr = device_arena_alloc(ptob(1), VM_NOSLEEP);
iommu->aiomt_va = (uintptr_t)device_arena_alloc(
extern void *device_arena_alloc(size_t size, int vm_flag);
cvaddr = device_arena_alloc(ptob(npages), VM_NOSLEEP);
extern void *device_arena_alloc(size_t size, int vm_flag);
cvaddr = device_arena_alloc(ptob(npages), VM_NOSLEEP);
extern void *device_arena_alloc(size_t size, int vm_flag);