/* SPDX-License-Identifier: MIT */ /** * @file * @section AUTHORS * * Copyright (C) 2010 Rafal Wojtczuk <rafal@invisiblethingslab.com> * * Authors: * Rafal Wojtczuk <rafal@invisiblethingslab.com> * Daniel De Graaf <dgdegra@tycho.nsa.gov> * * @section LICENSE * * @section DESCRIPTION * * Originally borrowed from the Qubes OS Project, http://www.qubes-os.org, * this code has been substantially rewritten to use the gntdev and gntalloc * devices instead of raw MFNs and map_foreign_range. * * This is a library for inter-domain communication. A standard Xen ring * buffer is used, with a datagram-based interface built on top. The grant * reference and event channels are shared in XenStore under a user-specified * path. * * The ring.h macros define an asymmetric interface to a shared data structure * that assumes all rings reside in a single contiguous memory space. This is * not suitable for vchan because the interface to the ring is symmetric except * for the setup. Unlike the producer-consumer rings defined in ring.h, the * size of the rings used in vchan are determined at execution time instead of * compile time, so the macros in ring.h cannot be used to access the rings. */ #include <stdint.h> #include <sys/types.h> struct ring_shared { uint32_t cons, prod; }; #define VCHAN_NOTIFY_WRITE 0x1 #define VCHAN_NOTIFY_READ 0x2 /** * vchan_interface: primary shared data structure */ struct vchan_interface { /** * Standard consumer/producer interface, one pair per buffer * left is client write, server read * right is client read, server write */ struct ring_shared left, right; /** * size of the rings, which determines their location * 10 - at offset 1024 in ring's page * 11 - at offset 2048 in ring's page * 12+ - uses 2^(N-12) grants to describe the multi-page ring * These should remain constant once the page is shared. * Only one of the two orders can be 10 (or 11). */ uint16_t left_order, right_order; /** * Shutdown detection: * 0: client (or server) has exited * 1: client (or server) is connected * 2: client has not yet connected */ uint8_t cli_live, srv_live; /** * Notification bits: * VCHAN_NOTIFY_WRITE: send notify when data is written * VCHAN_NOTIFY_READ: send notify when data is read (consumed) * cli_notify is used for the client to inform the server of its action */ uint8_t cli_notify, srv_notify; /** * Grant list: ordering is left, right. Must not extend into actual ring * or grow beyond the end of the initial shared page. * These should remain constant once the page is shared, to allow * for possible remapping by a client that restarts. */ uint32_t grants[0]; };