diff options
Diffstat (limited to 'util/vhost-user-server.c')
| -rw-r--r-- | util/vhost-user-server.c | 446 |
1 files changed, 446 insertions, 0 deletions
diff --git a/util/vhost-user-server.c b/util/vhost-user-server.c new file mode 100644 index 0000000000..783d847a6d --- /dev/null +++ b/util/vhost-user-server.c @@ -0,0 +1,446 @@ +/* + * Sharing QEMU devices via vhost-user protocol + * + * Copyright (c) Coiby Xu <coiby.xu@gmail.com>. + * Copyright (c) 2020 Red Hat, Inc. + * + * This work is licensed under the terms of the GNU GPL, version 2 or + * later. See the COPYING file in the top-level directory. + */ +#include "qemu/osdep.h" +#include "qemu/main-loop.h" +#include "qemu/vhost-user-server.h" +#include "block/aio-wait.h" + +/* + * Theory of operation: + * + * VuServer is started and stopped by vhost_user_server_start() and + * vhost_user_server_stop() from the main loop thread. Starting the server + * opens a vhost-user UNIX domain socket and listens for incoming connections. + * Only one connection is allowed at a time. + * + * The connection is handled by the vu_client_trip() coroutine in the + * VuServer->ctx AioContext. The coroutine consists of a vu_dispatch() loop + * where libvhost-user calls vu_message_read() to receive the next vhost-user + * protocol messages over the UNIX domain socket. + * + * When virtqueues are set up libvhost-user calls set_watch() to monitor kick + * fds. These fds are also handled in the VuServer->ctx AioContext. + * + * Both vu_client_trip() and kick fd monitoring can be stopped by shutting down + * the socket connection. Shutting down the socket connection causes + * vu_message_read() to fail since no more data can be received from the socket. + * After vu_dispatch() fails, vu_client_trip() calls vu_deinit() to stop + * libvhost-user before terminating the coroutine. vu_deinit() calls + * remove_watch() to stop monitoring kick fds and this stops virtqueue + * processing. + * + * When vu_client_trip() has finished cleaning up it schedules a BH in the main + * loop thread to accept the next client connection. + * + * When libvhost-user detects an error it calls panic_cb() and sets the + * dev->broken flag. Both vu_client_trip() and kick fd processing stop when + * the dev->broken flag is set. + * + * It is possible to switch AioContexts using + * vhost_user_server_detach_aio_context() and + * vhost_user_server_attach_aio_context(). They stop monitoring fds in the old + * AioContext and resume monitoring in the new AioContext. The vu_client_trip() + * coroutine remains in a yielded state during the switch. This is made + * possible by QIOChannel's support for spurious coroutine re-entry in + * qio_channel_yield(). The coroutine will restart I/O when re-entered from the + * new AioContext. + */ + +static void vmsg_close_fds(VhostUserMsg *vmsg) +{ + int i; + for (i = 0; i < vmsg->fd_num; i++) { + close(vmsg->fds[i]); + } +} + +static void vmsg_unblock_fds(VhostUserMsg *vmsg) +{ + int i; + for (i = 0; i < vmsg->fd_num; i++) { + qemu_set_nonblock(vmsg->fds[i]); + } +} + +static void panic_cb(VuDev *vu_dev, const char *buf) +{ + error_report("vu_panic: %s", buf); +} + +static bool coroutine_fn +vu_message_read(VuDev *vu_dev, int conn_fd, VhostUserMsg *vmsg) +{ + struct iovec iov = { + .iov_base = (char *)vmsg, + .iov_len = VHOST_USER_HDR_SIZE, + }; + int rc, read_bytes = 0; + Error *local_err = NULL; + const size_t max_fds = G_N_ELEMENTS(vmsg->fds); + VuServer *server = container_of(vu_dev, VuServer, vu_dev); + QIOChannel *ioc = server->ioc; + + vmsg->fd_num = 0; + if (!ioc) { + error_report_err(local_err); + goto fail; + } + + assert(qemu_in_coroutine()); + do { + size_t nfds = 0; + int *fds = NULL; + + /* + * qio_channel_readv_full may have short reads, keeping calling it + * until getting VHOST_USER_HDR_SIZE or 0 bytes in total + */ + rc = qio_channel_readv_full(ioc, &iov, 1, &fds, &nfds, &local_err); + if (rc < 0) { + if (rc == QIO_CHANNEL_ERR_BLOCK) { + assert(local_err == NULL); + qio_channel_yield(ioc, G_IO_IN); + continue; + } else { + error_report_err(local_err); + goto fail; + } + } + + if (nfds > 0) { + if (vmsg->fd_num + nfds > max_fds) { + error_report("A maximum of %zu fds are allowed, " + "however got %zu fds now", + max_fds, vmsg->fd_num + nfds); + g_free(fds); + goto fail; + } + memcpy(vmsg->fds + vmsg->fd_num, fds, nfds * sizeof(vmsg->fds[0])); + vmsg->fd_num += nfds; + g_free(fds); + } + + if (rc == 0) { /* socket closed */ + goto fail; + } + + iov.iov_base += rc; + iov.iov_len -= rc; + read_bytes += rc; + } while (read_bytes != VHOST_USER_HDR_SIZE); + + /* qio_channel_readv_full will make socket fds blocking, unblock them */ + vmsg_unblock_fds(vmsg); + if (vmsg->size > sizeof(vmsg->payload)) { + error_report("Error: too big message request: %d, " + "size: vmsg->size: %u, " + "while sizeof(vmsg->payload) = %zu", + vmsg->request, vmsg->size, sizeof(vmsg->payload)); + goto fail; + } + + struct iovec iov_payload = { + .iov_base = (char *)&vmsg->payload, + .iov_len = vmsg->size, + }; + if (vmsg->size) { + rc = qio_channel_readv_all_eof(ioc, &iov_payload, 1, &local_err); + if (rc != 1) { + if (local_err) { + error_report_err(local_err); + } + goto fail; + } + } + + return true; + +fail: + vmsg_close_fds(vmsg); + + return false; +} + +static coroutine_fn void vu_client_trip(void *opaque) +{ + VuServer *server = opaque; + VuDev *vu_dev = &server->vu_dev; + + while (!vu_dev->broken && vu_dispatch(vu_dev)) { + /* Keep running */ + } + + vu_deinit(vu_dev); + + /* vu_deinit() should have called remove_watch() */ + assert(QTAILQ_EMPTY(&server->vu_fd_watches)); + + object_unref(OBJECT(server->sioc)); + server->sioc = NULL; + + object_unref(OBJECT(server->ioc)); + server->ioc = NULL; + + server->co_trip = NULL; + if (server->restart_listener_bh) { + qemu_bh_schedule(server->restart_listener_bh); + } + aio_wait_kick(); +} + +/* + * a wrapper for vu_kick_cb + * + * since aio_dispatch can only pass one user data pointer to the + * callback function, pack VuDev and pvt into a struct. Then unpack it + * and pass them to vu_kick_cb + */ +static void kick_handler(void *opaque) +{ + VuFdWatch *vu_fd_watch = opaque; + VuDev *vu_dev = vu_fd_watch->vu_dev; + + vu_fd_watch->cb(vu_dev, 0, vu_fd_watch->pvt); + + /* Stop vu_client_trip() if an error occurred in vu_fd_watch->cb() */ + if (vu_dev->broken) { + VuServer *server = container_of(vu_dev, VuServer, vu_dev); + + qio_channel_shutdown(server->ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL); + } +} + +static VuFdWatch *find_vu_fd_watch(VuServer *server, int fd) +{ + + VuFdWatch *vu_fd_watch, *next; + QTAILQ_FOREACH_SAFE(vu_fd_watch, &server->vu_fd_watches, next, next) { + if (vu_fd_watch->fd == fd) { + return vu_fd_watch; + } + } + return NULL; +} + +static void +set_watch(VuDev *vu_dev, int fd, int vu_evt, + vu_watch_cb cb, void *pvt) +{ + + VuServer *server = container_of(vu_dev, VuServer, vu_dev); + g_assert(vu_dev); + g_assert(fd >= 0); + g_assert(cb); + + VuFdWatch *vu_fd_watch = find_vu_fd_watch(server, fd); + + if (!vu_fd_watch) { + VuFdWatch *vu_fd_watch = g_new0(VuFdWatch, 1); + + QTAILQ_INSERT_TAIL(&server->vu_fd_watches, vu_fd_watch, next); + + vu_fd_watch->fd = fd; + vu_fd_watch->cb = cb; + qemu_set_nonblock(fd); + aio_set_fd_handler(server->ioc->ctx, fd, true, kick_handler, + NULL, NULL, vu_fd_watch); + vu_fd_watch->vu_dev = vu_dev; + vu_fd_watch->pvt = pvt; + } +} + + +static void remove_watch(VuDev *vu_dev, int fd) +{ + VuServer *server; + g_assert(vu_dev); + g_assert(fd >= 0); + + server = container_of(vu_dev, VuServer, vu_dev); + + VuFdWatch *vu_fd_watch = find_vu_fd_watch(server, fd); + + if (!vu_fd_watch) { + return; + } + aio_set_fd_handler(server->ioc->ctx, fd, true, NULL, NULL, NULL, NULL); + + QTAILQ_REMOVE(&server->vu_fd_watches, vu_fd_watch, next); + g_free(vu_fd_watch); +} + + +static void vu_accept(QIONetListener *listener, QIOChannelSocket *sioc, + gpointer opaque) +{ + VuServer *server = opaque; + + if (server->sioc) { + warn_report("Only one vhost-user client is allowed to " + "connect the server one time"); + return; + } + + if (!vu_init(&server->vu_dev, server->max_queues, sioc->fd, panic_cb, + vu_message_read, set_watch, remove_watch, server->vu_iface)) { + error_report("Failed to initialize libvhost-user"); + return; + } + + /* + * Unset the callback function for network listener to make another + * vhost-user client keeping waiting until this client disconnects + */ + qio_net_listener_set_client_func(server->listener, + NULL, + NULL, + NULL); + server->sioc = sioc; + /* + * Increase the object reference, so sioc will not freed by + * qio_net_listener_channel_func which will call object_unref(OBJECT(sioc)) + */ + object_ref(OBJECT(server->sioc)); + qio_channel_set_name(QIO_CHANNEL(sioc), "vhost-user client"); + server->ioc = QIO_CHANNEL(sioc); + object_ref(OBJECT(server->ioc)); + + /* TODO vu_message_write() spins if non-blocking! */ + qio_channel_set_blocking(server->ioc, false, NULL); + + server->co_trip = qemu_coroutine_create(vu_client_trip, server); + + aio_context_acquire(server->ctx); + vhost_user_server_attach_aio_context(server, server->ctx); + aio_context_release(server->ctx); +} + +void vhost_user_server_stop(VuServer *server) +{ + aio_context_acquire(server->ctx); + + qemu_bh_delete(server->restart_listener_bh); + server->restart_listener_bh = NULL; + + if (server->sioc) { + VuFdWatch *vu_fd_watch; + + QTAILQ_FOREACH(vu_fd_watch, &server->vu_fd_watches, next) { + aio_set_fd_handler(server->ctx, vu_fd_watch->fd, true, + NULL, NULL, NULL, vu_fd_watch); + } + + qio_channel_shutdown(server->ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL); + + AIO_WAIT_WHILE(server->ctx, server->co_trip); + } + + aio_context_release(server->ctx); + + if (server->listener) { + qio_net_listener_disconnect(server->listener); + object_unref(OBJECT(server->listener)); + } +} + +/* + * Allow the next client to connect to the server. Called from a BH in the main + * loop. + */ +static void restart_listener_bh(void *opaque) +{ + VuServer *server = opaque; + + qio_net_listener_set_client_func(server->listener, vu_accept, server, + NULL); +} + +/* Called with ctx acquired */ +void vhost_user_server_attach_aio_context(VuServer *server, AioContext *ctx) +{ + VuFdWatch *vu_fd_watch; + + server->ctx = ctx; + + if (!server->sioc) { + return; + } + + qio_channel_attach_aio_context(server->ioc, ctx); + + QTAILQ_FOREACH(vu_fd_watch, &server->vu_fd_watches, next) { + aio_set_fd_handler(ctx, vu_fd_watch->fd, true, kick_handler, NULL, + NULL, vu_fd_watch); + } + + aio_co_schedule(ctx, server->co_trip); +} + +/* Called with server->ctx acquired */ +void vhost_user_server_detach_aio_context(VuServer *server) +{ + if (server->sioc) { + VuFdWatch *vu_fd_watch; + + QTAILQ_FOREACH(vu_fd_watch, &server->vu_fd_watches, next) { + aio_set_fd_handler(server->ctx, vu_fd_watch->fd, true, + NULL, NULL, NULL, vu_fd_watch); + } + + qio_channel_detach_aio_context(server->ioc); + } + + server->ctx = NULL; +} + +bool vhost_user_server_start(VuServer *server, + SocketAddress *socket_addr, + AioContext *ctx, + uint16_t max_queues, + const VuDevIface *vu_iface, + Error **errp) +{ + QEMUBH *bh; + QIONetListener *listener; + + if (socket_addr->type != SOCKET_ADDRESS_TYPE_UNIX && + socket_addr->type != SOCKET_ADDRESS_TYPE_FD) { + error_setg(errp, "Only socket address types 'unix' and 'fd' are supported"); + return false; + } + + listener = qio_net_listener_new(); + if (qio_net_listener_open_sync(listener, socket_addr, 1, + errp) < 0) { + object_unref(OBJECT(listener)); + return false; + } + + bh = qemu_bh_new(restart_listener_bh, server); + + /* zero out unspecified fields */ + *server = (VuServer) { + .listener = listener, + .restart_listener_bh = bh, + .vu_iface = vu_iface, + .max_queues = max_queues, + .ctx = ctx, + }; + + qio_net_listener_set_name(server->listener, "vhost-user-backend-listener"); + + qio_net_listener_set_client_func(server->listener, + vu_accept, + server, + NULL); + + QTAILQ_INIT(&server->vu_fd_watches); + return true; +} |