1 /* SPDX-License-Identifier: MIT */ 2 /** 3 * @file 4 * @section AUTHORS 5 * 6 * Copyright (C) 2010 Rafal Wojtczuk <rafal@invisiblethingslab.com> 7 * 8 * Authors: 9 * Rafal Wojtczuk <rafal@invisiblethingslab.com> 10 * Daniel De Graaf <dgdegra@tycho.nsa.gov> 11 * 12 * @section LICENSE 13 * 14 * @section DESCRIPTION 15 * 16 * Originally borrowed from the Qubes OS Project, http://www.qubes-os.org, 17 * this code has been substantially rewritten to use the gntdev and gntalloc 18 * devices instead of raw MFNs and map_foreign_range. 19 * 20 * This is a library for inter-domain communication. A standard Xen ring 21 * buffer is used, with a datagram-based interface built on top. The grant 22 * reference and event channels are shared in XenStore under a user-specified 23 * path. 24 * 25 * The ring.h macros define an asymmetric interface to a shared data structure 26 * that assumes all rings reside in a single contiguous memory space. This is 27 * not suitable for vchan because the interface to the ring is symmetric except 28 * for the setup. Unlike the producer-consumer rings defined in ring.h, the 29 * size of the rings used in vchan are determined at execution time instead of 30 * compile time, so the macros in ring.h cannot be used to access the rings. 31 */ 32 33 #include <stdint.h> 34 #include <sys/types.h> 35 36 struct ring_shared { 37 uint32_t cons, prod; 38 }; 39 40 #define VCHAN_NOTIFY_WRITE 0x1 41 #define VCHAN_NOTIFY_READ 0x2 42 43 /** 44 * vchan_interface: primary shared data structure 45 */ 46 struct vchan_interface { 47 /** 48 * Standard consumer/producer interface, one pair per buffer 49 * left is client write, server read 50 * right is client read, server write 51 */ 52 struct ring_shared left, right; 53 /** 54 * size of the rings, which determines their location 55 * 10 - at offset 1024 in ring's page 56 * 11 - at offset 2048 in ring's page 57 * 12+ - uses 2^(N-12) grants to describe the multi-page ring 58 * These should remain constant once the page is shared. 59 * Only one of the two orders can be 10 (or 11). 60 */ 61 uint16_t left_order, right_order; 62 /** 63 * Shutdown detection: 64 * 0: client (or server) has exited 65 * 1: client (or server) is connected 66 * 2: client has not yet connected 67 */ 68 uint8_t cli_live, srv_live; 69 /** 70 * Notification bits: 71 * VCHAN_NOTIFY_WRITE: send notify when data is written 72 * VCHAN_NOTIFY_READ: send notify when data is read (consumed) 73 * cli_notify is used for the client to inform the server of its action 74 */ 75 uint8_t cli_notify, srv_notify; 76 /** 77 * Grant list: ordering is left, right. Must not extend into actual ring 78 * or grow beyond the end of the initial shared page. 79 * These should remain constant once the page is shared, to allow 80 * for possible remapping by a client that restarts. 81 */ 82 uint32_t grants[0]; 83 }; 84 85