Merge remote-tracking branch 'remotes/pmaydell/tags/pull-target-arm-20210330' into...
[qemu/ar7.git] / util / vhost-user-server.c
blob783d847a6db3021d16fb1048e751167818119b24
1 /*
2 * Sharing QEMU devices via vhost-user protocol
4 * Copyright (c) Coiby Xu <coiby.xu@gmail.com>.
5 * Copyright (c) 2020 Red Hat, Inc.
7 * This work is licensed under the terms of the GNU GPL, version 2 or
8 * later. See the COPYING file in the top-level directory.
9 */
10 #include "qemu/osdep.h"
11 #include "qemu/main-loop.h"
12 #include "qemu/vhost-user-server.h"
13 #include "block/aio-wait.h"
16 * Theory of operation:
18 * VuServer is started and stopped by vhost_user_server_start() and
19 * vhost_user_server_stop() from the main loop thread. Starting the server
20 * opens a vhost-user UNIX domain socket and listens for incoming connections.
21 * Only one connection is allowed at a time.
23 * The connection is handled by the vu_client_trip() coroutine in the
24 * VuServer->ctx AioContext. The coroutine consists of a vu_dispatch() loop
25 * where libvhost-user calls vu_message_read() to receive the next vhost-user
26 * protocol messages over the UNIX domain socket.
28 * When virtqueues are set up libvhost-user calls set_watch() to monitor kick
29 * fds. These fds are also handled in the VuServer->ctx AioContext.
31 * Both vu_client_trip() and kick fd monitoring can be stopped by shutting down
32 * the socket connection. Shutting down the socket connection causes
33 * vu_message_read() to fail since no more data can be received from the socket.
34 * After vu_dispatch() fails, vu_client_trip() calls vu_deinit() to stop
35 * libvhost-user before terminating the coroutine. vu_deinit() calls
36 * remove_watch() to stop monitoring kick fds and this stops virtqueue
37 * processing.
39 * When vu_client_trip() has finished cleaning up it schedules a BH in the main
40 * loop thread to accept the next client connection.
42 * When libvhost-user detects an error it calls panic_cb() and sets the
43 * dev->broken flag. Both vu_client_trip() and kick fd processing stop when
44 * the dev->broken flag is set.
46 * It is possible to switch AioContexts using
47 * vhost_user_server_detach_aio_context() and
48 * vhost_user_server_attach_aio_context(). They stop monitoring fds in the old
49 * AioContext and resume monitoring in the new AioContext. The vu_client_trip()
50 * coroutine remains in a yielded state during the switch. This is made
51 * possible by QIOChannel's support for spurious coroutine re-entry in
52 * qio_channel_yield(). The coroutine will restart I/O when re-entered from the
53 * new AioContext.
56 static void vmsg_close_fds(VhostUserMsg *vmsg)
58 int i;
59 for (i = 0; i < vmsg->fd_num; i++) {
60 close(vmsg->fds[i]);
64 static void vmsg_unblock_fds(VhostUserMsg *vmsg)
66 int i;
67 for (i = 0; i < vmsg->fd_num; i++) {
68 qemu_set_nonblock(vmsg->fds[i]);
72 static void panic_cb(VuDev *vu_dev, const char *buf)
74 error_report("vu_panic: %s", buf);
77 static bool coroutine_fn
78 vu_message_read(VuDev *vu_dev, int conn_fd, VhostUserMsg *vmsg)
80 struct iovec iov = {
81 .iov_base = (char *)vmsg,
82 .iov_len = VHOST_USER_HDR_SIZE,
84 int rc, read_bytes = 0;
85 Error *local_err = NULL;
86 const size_t max_fds = G_N_ELEMENTS(vmsg->fds);
87 VuServer *server = container_of(vu_dev, VuServer, vu_dev);
88 QIOChannel *ioc = server->ioc;
90 vmsg->fd_num = 0;
91 if (!ioc) {
92 error_report_err(local_err);
93 goto fail;
96 assert(qemu_in_coroutine());
97 do {
98 size_t nfds = 0;
99 int *fds = NULL;
102 * qio_channel_readv_full may have short reads, keeping calling it
103 * until getting VHOST_USER_HDR_SIZE or 0 bytes in total
105 rc = qio_channel_readv_full(ioc, &iov, 1, &fds, &nfds, &local_err);
106 if (rc < 0) {
107 if (rc == QIO_CHANNEL_ERR_BLOCK) {
108 assert(local_err == NULL);
109 qio_channel_yield(ioc, G_IO_IN);
110 continue;
111 } else {
112 error_report_err(local_err);
113 goto fail;
117 if (nfds > 0) {
118 if (vmsg->fd_num + nfds > max_fds) {
119 error_report("A maximum of %zu fds are allowed, "
120 "however got %zu fds now",
121 max_fds, vmsg->fd_num + nfds);
122 g_free(fds);
123 goto fail;
125 memcpy(vmsg->fds + vmsg->fd_num, fds, nfds * sizeof(vmsg->fds[0]));
126 vmsg->fd_num += nfds;
127 g_free(fds);
130 if (rc == 0) { /* socket closed */
131 goto fail;
134 iov.iov_base += rc;
135 iov.iov_len -= rc;
136 read_bytes += rc;
137 } while (read_bytes != VHOST_USER_HDR_SIZE);
139 /* qio_channel_readv_full will make socket fds blocking, unblock them */
140 vmsg_unblock_fds(vmsg);
141 if (vmsg->size > sizeof(vmsg->payload)) {
142 error_report("Error: too big message request: %d, "
143 "size: vmsg->size: %u, "
144 "while sizeof(vmsg->payload) = %zu",
145 vmsg->request, vmsg->size, sizeof(vmsg->payload));
146 goto fail;
149 struct iovec iov_payload = {
150 .iov_base = (char *)&vmsg->payload,
151 .iov_len = vmsg->size,
153 if (vmsg->size) {
154 rc = qio_channel_readv_all_eof(ioc, &iov_payload, 1, &local_err);
155 if (rc != 1) {
156 if (local_err) {
157 error_report_err(local_err);
159 goto fail;
163 return true;
165 fail:
166 vmsg_close_fds(vmsg);
168 return false;
171 static coroutine_fn void vu_client_trip(void *opaque)
173 VuServer *server = opaque;
174 VuDev *vu_dev = &server->vu_dev;
176 while (!vu_dev->broken && vu_dispatch(vu_dev)) {
177 /* Keep running */
180 vu_deinit(vu_dev);
182 /* vu_deinit() should have called remove_watch() */
183 assert(QTAILQ_EMPTY(&server->vu_fd_watches));
185 object_unref(OBJECT(server->sioc));
186 server->sioc = NULL;
188 object_unref(OBJECT(server->ioc));
189 server->ioc = NULL;
191 server->co_trip = NULL;
192 if (server->restart_listener_bh) {
193 qemu_bh_schedule(server->restart_listener_bh);
195 aio_wait_kick();
199 * a wrapper for vu_kick_cb
201 * since aio_dispatch can only pass one user data pointer to the
202 * callback function, pack VuDev and pvt into a struct. Then unpack it
203 * and pass them to vu_kick_cb
205 static void kick_handler(void *opaque)
207 VuFdWatch *vu_fd_watch = opaque;
208 VuDev *vu_dev = vu_fd_watch->vu_dev;
210 vu_fd_watch->cb(vu_dev, 0, vu_fd_watch->pvt);
212 /* Stop vu_client_trip() if an error occurred in vu_fd_watch->cb() */
213 if (vu_dev->broken) {
214 VuServer *server = container_of(vu_dev, VuServer, vu_dev);
216 qio_channel_shutdown(server->ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
220 static VuFdWatch *find_vu_fd_watch(VuServer *server, int fd)
223 VuFdWatch *vu_fd_watch, *next;
224 QTAILQ_FOREACH_SAFE(vu_fd_watch, &server->vu_fd_watches, next, next) {
225 if (vu_fd_watch->fd == fd) {
226 return vu_fd_watch;
229 return NULL;
232 static void
233 set_watch(VuDev *vu_dev, int fd, int vu_evt,
234 vu_watch_cb cb, void *pvt)
237 VuServer *server = container_of(vu_dev, VuServer, vu_dev);
238 g_assert(vu_dev);
239 g_assert(fd >= 0);
240 g_assert(cb);
242 VuFdWatch *vu_fd_watch = find_vu_fd_watch(server, fd);
244 if (!vu_fd_watch) {
245 VuFdWatch *vu_fd_watch = g_new0(VuFdWatch, 1);
247 QTAILQ_INSERT_TAIL(&server->vu_fd_watches, vu_fd_watch, next);
249 vu_fd_watch->fd = fd;
250 vu_fd_watch->cb = cb;
251 qemu_set_nonblock(fd);
252 aio_set_fd_handler(server->ioc->ctx, fd, true, kick_handler,
253 NULL, NULL, vu_fd_watch);
254 vu_fd_watch->vu_dev = vu_dev;
255 vu_fd_watch->pvt = pvt;
260 static void remove_watch(VuDev *vu_dev, int fd)
262 VuServer *server;
263 g_assert(vu_dev);
264 g_assert(fd >= 0);
266 server = container_of(vu_dev, VuServer, vu_dev);
268 VuFdWatch *vu_fd_watch = find_vu_fd_watch(server, fd);
270 if (!vu_fd_watch) {
271 return;
273 aio_set_fd_handler(server->ioc->ctx, fd, true, NULL, NULL, NULL, NULL);
275 QTAILQ_REMOVE(&server->vu_fd_watches, vu_fd_watch, next);
276 g_free(vu_fd_watch);
280 static void vu_accept(QIONetListener *listener, QIOChannelSocket *sioc,
281 gpointer opaque)
283 VuServer *server = opaque;
285 if (server->sioc) {
286 warn_report("Only one vhost-user client is allowed to "
287 "connect the server one time");
288 return;
291 if (!vu_init(&server->vu_dev, server->max_queues, sioc->fd, panic_cb,
292 vu_message_read, set_watch, remove_watch, server->vu_iface)) {
293 error_report("Failed to initialize libvhost-user");
294 return;
298 * Unset the callback function for network listener to make another
299 * vhost-user client keeping waiting until this client disconnects
301 qio_net_listener_set_client_func(server->listener,
302 NULL,
303 NULL,
304 NULL);
305 server->sioc = sioc;
307 * Increase the object reference, so sioc will not freed by
308 * qio_net_listener_channel_func which will call object_unref(OBJECT(sioc))
310 object_ref(OBJECT(server->sioc));
311 qio_channel_set_name(QIO_CHANNEL(sioc), "vhost-user client");
312 server->ioc = QIO_CHANNEL(sioc);
313 object_ref(OBJECT(server->ioc));
315 /* TODO vu_message_write() spins if non-blocking! */
316 qio_channel_set_blocking(server->ioc, false, NULL);
318 server->co_trip = qemu_coroutine_create(vu_client_trip, server);
320 aio_context_acquire(server->ctx);
321 vhost_user_server_attach_aio_context(server, server->ctx);
322 aio_context_release(server->ctx);
325 void vhost_user_server_stop(VuServer *server)
327 aio_context_acquire(server->ctx);
329 qemu_bh_delete(server->restart_listener_bh);
330 server->restart_listener_bh = NULL;
332 if (server->sioc) {
333 VuFdWatch *vu_fd_watch;
335 QTAILQ_FOREACH(vu_fd_watch, &server->vu_fd_watches, next) {
336 aio_set_fd_handler(server->ctx, vu_fd_watch->fd, true,
337 NULL, NULL, NULL, vu_fd_watch);
340 qio_channel_shutdown(server->ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
342 AIO_WAIT_WHILE(server->ctx, server->co_trip);
345 aio_context_release(server->ctx);
347 if (server->listener) {
348 qio_net_listener_disconnect(server->listener);
349 object_unref(OBJECT(server->listener));
354 * Allow the next client to connect to the server. Called from a BH in the main
355 * loop.
357 static void restart_listener_bh(void *opaque)
359 VuServer *server = opaque;
361 qio_net_listener_set_client_func(server->listener, vu_accept, server,
362 NULL);
365 /* Called with ctx acquired */
366 void vhost_user_server_attach_aio_context(VuServer *server, AioContext *ctx)
368 VuFdWatch *vu_fd_watch;
370 server->ctx = ctx;
372 if (!server->sioc) {
373 return;
376 qio_channel_attach_aio_context(server->ioc, ctx);
378 QTAILQ_FOREACH(vu_fd_watch, &server->vu_fd_watches, next) {
379 aio_set_fd_handler(ctx, vu_fd_watch->fd, true, kick_handler, NULL,
380 NULL, vu_fd_watch);
383 aio_co_schedule(ctx, server->co_trip);
386 /* Called with server->ctx acquired */
387 void vhost_user_server_detach_aio_context(VuServer *server)
389 if (server->sioc) {
390 VuFdWatch *vu_fd_watch;
392 QTAILQ_FOREACH(vu_fd_watch, &server->vu_fd_watches, next) {
393 aio_set_fd_handler(server->ctx, vu_fd_watch->fd, true,
394 NULL, NULL, NULL, vu_fd_watch);
397 qio_channel_detach_aio_context(server->ioc);
400 server->ctx = NULL;
403 bool vhost_user_server_start(VuServer *server,
404 SocketAddress *socket_addr,
405 AioContext *ctx,
406 uint16_t max_queues,
407 const VuDevIface *vu_iface,
408 Error **errp)
410 QEMUBH *bh;
411 QIONetListener *listener;
413 if (socket_addr->type != SOCKET_ADDRESS_TYPE_UNIX &&
414 socket_addr->type != SOCKET_ADDRESS_TYPE_FD) {
415 error_setg(errp, "Only socket address types 'unix' and 'fd' are supported");
416 return false;
419 listener = qio_net_listener_new();
420 if (qio_net_listener_open_sync(listener, socket_addr, 1,
421 errp) < 0) {
422 object_unref(OBJECT(listener));
423 return false;
426 bh = qemu_bh_new(restart_listener_bh, server);
428 /* zero out unspecified fields */
429 *server = (VuServer) {
430 .listener = listener,
431 .restart_listener_bh = bh,
432 .vu_iface = vu_iface,
433 .max_queues = max_queues,
434 .ctx = ctx,
437 qio_net_listener_set_name(server->listener, "vhost-user-backend-listener");
439 qio_net_listener_set_client_func(server->listener,
440 vu_accept,
441 server,
442 NULL);
444 QTAILQ_INIT(&server->vu_fd_watches);
445 return true;