-Lguest I/O model:
-
-Lguest uses a simplified DMA model plus shared memory for I/O. Guests
-can communicate with each other if they share underlying memory
-(usually by the lguest program mmaping the same file), but they can
-use any non-shared memory to communicate with the lguest process.
-
-Guests can register DMA buffers at any key (must be a valid physical
-address) using the LHCALL_BIND_DMA(key, dmabufs, num<<8|irq)
-hypercall. "dmabufs" is the physical address of an array of "num"
-"struct lguest_dma": each contains a used_len, and an array of
-physical addresses and lengths. When a transfer occurs, the
-"used_len" field of one of the buffers which has used_len 0 will be
-set to the length transferred and the irq will fire.