f51eea4b32
this patch changes the way pagefaults are delivered to VM. It adopts the same model as the out-of-quantum messages sent by kernel to a scheduler. - everytime a userspace pagefault occurs, kernel creates a message which is sent to VM on behalf of the faulting process - the process is blocked on delivery to VM in the standard IPC code instead of waiting in a spacial in-kernel queue (stack) and is not runnable until VM tell kernel that the pagefault is resolved and is free to clear the RTS_PAGEFAULT flag. - VM does not need call kernel and poll the pagefault information which saves many (1/2?) calls and kernel calls that return "no more data" - VM notification by kernel does not need to use signals - each entry in proc table is by 12 bytes smaller (~3k save)