DIRTY_BITMAP_BYTES
DIRTY_BITMAP_BYTES(nbits + shift)))
(bitmap_size < DIRTY_BITMAP_BYTES(npages)))
#define DIRTY_BITMAP_SIZE_MAX DIRTY_BITMAP_BYTES(DIRTY_BITMAP_PAGES_MAX)
dma->bitmap = kvzalloc(DIRTY_BITMAP_BYTES(npages) + sizeof(u64),