VirtioUsedItem
VirtioUsedItem ring[0];
queueMemSize += ROUNDUP(sizeof(VirtioUsed) + sizeof(VirtioUsedItem) * fQueueLen, B_PAGE_SIZE);
+ sizeof(VirtioUsedItem) * fQueueLen, 4096);
memset(fUsed, 0, sizeof(VirtioUsed) + sizeof(VirtioUsedItem) * fQueueLen);