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2957dc40a2
vhost_user_server_stop() uses AIO_WAIT_WHILE(). AIO_WAIT_WHILE() requires that AioContext is only acquired once. Since blk_exp_request_shutdown() already acquires the AioContext it shouldn't be acquired again in vhost_user_server_stop(). Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-Id: <20230323145853.1345527-1-stefanha@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
468 lines
14 KiB
C
468 lines
14 KiB
C
/*
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* Sharing QEMU devices via vhost-user protocol
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*
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* Copyright (c) Coiby Xu <coiby.xu@gmail.com>.
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* Copyright (c) 2020 Red Hat, Inc.
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or
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* later. See the COPYING file in the top-level directory.
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*/
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#include "qemu/osdep.h"
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#include "qemu/error-report.h"
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#include "qemu/main-loop.h"
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#include "qemu/vhost-user-server.h"
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#include "block/aio-wait.h"
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/*
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* Theory of operation:
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*
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* VuServer is started and stopped by vhost_user_server_start() and
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* vhost_user_server_stop() from the main loop thread. Starting the server
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* opens a vhost-user UNIX domain socket and listens for incoming connections.
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* Only one connection is allowed at a time.
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*
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* The connection is handled by the vu_client_trip() coroutine in the
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* VuServer->ctx AioContext. The coroutine consists of a vu_dispatch() loop
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* where libvhost-user calls vu_message_read() to receive the next vhost-user
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* protocol messages over the UNIX domain socket.
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*
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* When virtqueues are set up libvhost-user calls set_watch() to monitor kick
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* fds. These fds are also handled in the VuServer->ctx AioContext.
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*
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* Both vu_client_trip() and kick fd monitoring can be stopped by shutting down
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* the socket connection. Shutting down the socket connection causes
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* vu_message_read() to fail since no more data can be received from the socket.
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* After vu_dispatch() fails, vu_client_trip() calls vu_deinit() to stop
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* libvhost-user before terminating the coroutine. vu_deinit() calls
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* remove_watch() to stop monitoring kick fds and this stops virtqueue
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* processing.
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*
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* When vu_client_trip() has finished cleaning up it schedules a BH in the main
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* loop thread to accept the next client connection.
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*
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* When libvhost-user detects an error it calls panic_cb() and sets the
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* dev->broken flag. Both vu_client_trip() and kick fd processing stop when
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* the dev->broken flag is set.
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*
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* It is possible to switch AioContexts using
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* vhost_user_server_detach_aio_context() and
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* vhost_user_server_attach_aio_context(). They stop monitoring fds in the old
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* AioContext and resume monitoring in the new AioContext. The vu_client_trip()
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* coroutine remains in a yielded state during the switch. This is made
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* possible by QIOChannel's support for spurious coroutine re-entry in
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* qio_channel_yield(). The coroutine will restart I/O when re-entered from the
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* new AioContext.
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*/
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static void vmsg_close_fds(VhostUserMsg *vmsg)
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{
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int i;
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for (i = 0; i < vmsg->fd_num; i++) {
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close(vmsg->fds[i]);
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}
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}
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static void vmsg_unblock_fds(VhostUserMsg *vmsg)
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{
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int i;
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for (i = 0; i < vmsg->fd_num; i++) {
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qemu_socket_set_nonblock(vmsg->fds[i]);
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}
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}
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static void panic_cb(VuDev *vu_dev, const char *buf)
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{
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error_report("vu_panic: %s", buf);
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}
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void vhost_user_server_ref(VuServer *server)
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{
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assert(!server->wait_idle);
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server->refcount++;
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}
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void vhost_user_server_unref(VuServer *server)
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{
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server->refcount--;
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if (server->wait_idle && !server->refcount) {
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aio_co_wake(server->co_trip);
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}
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}
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static bool coroutine_fn
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vu_message_read(VuDev *vu_dev, int conn_fd, VhostUserMsg *vmsg)
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{
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struct iovec iov = {
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.iov_base = (char *)vmsg,
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.iov_len = VHOST_USER_HDR_SIZE,
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};
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int rc, read_bytes = 0;
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Error *local_err = NULL;
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const size_t max_fds = G_N_ELEMENTS(vmsg->fds);
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VuServer *server = container_of(vu_dev, VuServer, vu_dev);
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QIOChannel *ioc = server->ioc;
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vmsg->fd_num = 0;
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if (!ioc) {
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error_report_err(local_err);
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goto fail;
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}
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assert(qemu_in_coroutine());
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do {
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size_t nfds = 0;
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int *fds = NULL;
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/*
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* qio_channel_readv_full may have short reads, keeping calling it
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* until getting VHOST_USER_HDR_SIZE or 0 bytes in total
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*/
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rc = qio_channel_readv_full(ioc, &iov, 1, &fds, &nfds, 0, &local_err);
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if (rc < 0) {
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if (rc == QIO_CHANNEL_ERR_BLOCK) {
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assert(local_err == NULL);
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qio_channel_yield(ioc, G_IO_IN);
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continue;
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} else {
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error_report_err(local_err);
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goto fail;
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}
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}
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if (nfds > 0) {
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if (vmsg->fd_num + nfds > max_fds) {
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error_report("A maximum of %zu fds are allowed, "
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"however got %zu fds now",
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max_fds, vmsg->fd_num + nfds);
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g_free(fds);
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goto fail;
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}
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memcpy(vmsg->fds + vmsg->fd_num, fds, nfds * sizeof(vmsg->fds[0]));
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vmsg->fd_num += nfds;
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g_free(fds);
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}
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if (rc == 0) { /* socket closed */
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goto fail;
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}
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iov.iov_base += rc;
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iov.iov_len -= rc;
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read_bytes += rc;
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} while (read_bytes != VHOST_USER_HDR_SIZE);
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/* qio_channel_readv_full will make socket fds blocking, unblock them */
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vmsg_unblock_fds(vmsg);
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if (vmsg->size > sizeof(vmsg->payload)) {
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error_report("Error: too big message request: %d, "
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"size: vmsg->size: %u, "
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"while sizeof(vmsg->payload) = %zu",
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vmsg->request, vmsg->size, sizeof(vmsg->payload));
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goto fail;
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}
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struct iovec iov_payload = {
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.iov_base = (char *)&vmsg->payload,
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.iov_len = vmsg->size,
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};
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if (vmsg->size) {
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rc = qio_channel_readv_all_eof(ioc, &iov_payload, 1, &local_err);
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if (rc != 1) {
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if (local_err) {
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error_report_err(local_err);
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}
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goto fail;
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}
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}
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return true;
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fail:
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vmsg_close_fds(vmsg);
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return false;
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}
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static coroutine_fn void vu_client_trip(void *opaque)
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{
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VuServer *server = opaque;
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VuDev *vu_dev = &server->vu_dev;
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while (!vu_dev->broken && vu_dispatch(vu_dev)) {
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/* Keep running */
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}
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if (server->refcount) {
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/* Wait for requests to complete before we can unmap the memory */
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server->wait_idle = true;
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qemu_coroutine_yield();
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server->wait_idle = false;
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}
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assert(server->refcount == 0);
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vu_deinit(vu_dev);
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/* vu_deinit() should have called remove_watch() */
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assert(QTAILQ_EMPTY(&server->vu_fd_watches));
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object_unref(OBJECT(server->sioc));
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server->sioc = NULL;
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object_unref(OBJECT(server->ioc));
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server->ioc = NULL;
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server->co_trip = NULL;
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if (server->restart_listener_bh) {
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qemu_bh_schedule(server->restart_listener_bh);
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}
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aio_wait_kick();
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}
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/*
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* a wrapper for vu_kick_cb
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*
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* since aio_dispatch can only pass one user data pointer to the
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* callback function, pack VuDev and pvt into a struct. Then unpack it
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* and pass them to vu_kick_cb
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*/
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static void kick_handler(void *opaque)
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{
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VuFdWatch *vu_fd_watch = opaque;
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VuDev *vu_dev = vu_fd_watch->vu_dev;
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vu_fd_watch->cb(vu_dev, 0, vu_fd_watch->pvt);
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/* Stop vu_client_trip() if an error occurred in vu_fd_watch->cb() */
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if (vu_dev->broken) {
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VuServer *server = container_of(vu_dev, VuServer, vu_dev);
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qio_channel_shutdown(server->ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
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}
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}
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static VuFdWatch *find_vu_fd_watch(VuServer *server, int fd)
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{
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VuFdWatch *vu_fd_watch, *next;
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QTAILQ_FOREACH_SAFE(vu_fd_watch, &server->vu_fd_watches, next, next) {
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if (vu_fd_watch->fd == fd) {
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return vu_fd_watch;
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}
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}
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return NULL;
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}
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static void
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set_watch(VuDev *vu_dev, int fd, int vu_evt,
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vu_watch_cb cb, void *pvt)
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{
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VuServer *server = container_of(vu_dev, VuServer, vu_dev);
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g_assert(vu_dev);
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g_assert(fd >= 0);
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g_assert(cb);
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VuFdWatch *vu_fd_watch = find_vu_fd_watch(server, fd);
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if (!vu_fd_watch) {
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VuFdWatch *vu_fd_watch = g_new0(VuFdWatch, 1);
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QTAILQ_INSERT_TAIL(&server->vu_fd_watches, vu_fd_watch, next);
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vu_fd_watch->fd = fd;
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vu_fd_watch->cb = cb;
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qemu_socket_set_nonblock(fd);
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aio_set_fd_handler(server->ioc->ctx, fd, true, kick_handler,
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NULL, NULL, NULL, vu_fd_watch);
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vu_fd_watch->vu_dev = vu_dev;
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vu_fd_watch->pvt = pvt;
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}
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}
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static void remove_watch(VuDev *vu_dev, int fd)
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{
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VuServer *server;
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g_assert(vu_dev);
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g_assert(fd >= 0);
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server = container_of(vu_dev, VuServer, vu_dev);
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VuFdWatch *vu_fd_watch = find_vu_fd_watch(server, fd);
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if (!vu_fd_watch) {
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return;
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}
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aio_set_fd_handler(server->ioc->ctx, fd, true,
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NULL, NULL, NULL, NULL, NULL);
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QTAILQ_REMOVE(&server->vu_fd_watches, vu_fd_watch, next);
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g_free(vu_fd_watch);
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}
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static void vu_accept(QIONetListener *listener, QIOChannelSocket *sioc,
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gpointer opaque)
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{
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VuServer *server = opaque;
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if (server->sioc) {
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warn_report("Only one vhost-user client is allowed to "
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"connect the server one time");
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return;
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}
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if (!vu_init(&server->vu_dev, server->max_queues, sioc->fd, panic_cb,
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vu_message_read, set_watch, remove_watch, server->vu_iface)) {
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error_report("Failed to initialize libvhost-user");
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return;
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}
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/*
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* Unset the callback function for network listener to make another
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* vhost-user client keeping waiting until this client disconnects
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*/
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qio_net_listener_set_client_func(server->listener,
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NULL,
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NULL,
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NULL);
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server->sioc = sioc;
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/*
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* Increase the object reference, so sioc will not freed by
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* qio_net_listener_channel_func which will call object_unref(OBJECT(sioc))
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*/
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object_ref(OBJECT(server->sioc));
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qio_channel_set_name(QIO_CHANNEL(sioc), "vhost-user client");
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server->ioc = QIO_CHANNEL(sioc);
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object_ref(OBJECT(server->ioc));
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/* TODO vu_message_write() spins if non-blocking! */
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qio_channel_set_blocking(server->ioc, false, NULL);
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server->co_trip = qemu_coroutine_create(vu_client_trip, server);
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aio_context_acquire(server->ctx);
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vhost_user_server_attach_aio_context(server, server->ctx);
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aio_context_release(server->ctx);
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}
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/* server->ctx acquired by caller */
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void vhost_user_server_stop(VuServer *server)
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{
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qemu_bh_delete(server->restart_listener_bh);
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server->restart_listener_bh = NULL;
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if (server->sioc) {
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VuFdWatch *vu_fd_watch;
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QTAILQ_FOREACH(vu_fd_watch, &server->vu_fd_watches, next) {
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aio_set_fd_handler(server->ctx, vu_fd_watch->fd, true,
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NULL, NULL, NULL, NULL, vu_fd_watch);
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}
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qio_channel_shutdown(server->ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
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AIO_WAIT_WHILE(server->ctx, server->co_trip);
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}
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if (server->listener) {
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qio_net_listener_disconnect(server->listener);
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object_unref(OBJECT(server->listener));
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}
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}
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/*
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* Allow the next client to connect to the server. Called from a BH in the main
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* loop.
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*/
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static void restart_listener_bh(void *opaque)
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{
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VuServer *server = opaque;
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qio_net_listener_set_client_func(server->listener, vu_accept, server,
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NULL);
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}
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/* Called with ctx acquired */
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void vhost_user_server_attach_aio_context(VuServer *server, AioContext *ctx)
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{
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VuFdWatch *vu_fd_watch;
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server->ctx = ctx;
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if (!server->sioc) {
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return;
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}
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qio_channel_attach_aio_context(server->ioc, ctx);
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QTAILQ_FOREACH(vu_fd_watch, &server->vu_fd_watches, next) {
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aio_set_fd_handler(ctx, vu_fd_watch->fd, true, kick_handler, NULL,
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NULL, NULL, vu_fd_watch);
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}
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aio_co_schedule(ctx, server->co_trip);
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}
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/* Called with server->ctx acquired */
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void vhost_user_server_detach_aio_context(VuServer *server)
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{
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if (server->sioc) {
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VuFdWatch *vu_fd_watch;
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QTAILQ_FOREACH(vu_fd_watch, &server->vu_fd_watches, next) {
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aio_set_fd_handler(server->ctx, vu_fd_watch->fd, true,
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NULL, NULL, NULL, NULL, vu_fd_watch);
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}
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qio_channel_detach_aio_context(server->ioc);
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}
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server->ctx = NULL;
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}
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bool vhost_user_server_start(VuServer *server,
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SocketAddress *socket_addr,
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AioContext *ctx,
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uint16_t max_queues,
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const VuDevIface *vu_iface,
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Error **errp)
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{
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QEMUBH *bh;
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QIONetListener *listener;
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if (socket_addr->type != SOCKET_ADDRESS_TYPE_UNIX &&
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socket_addr->type != SOCKET_ADDRESS_TYPE_FD) {
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error_setg(errp, "Only socket address types 'unix' and 'fd' are supported");
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return false;
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}
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listener = qio_net_listener_new();
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if (qio_net_listener_open_sync(listener, socket_addr, 1,
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errp) < 0) {
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object_unref(OBJECT(listener));
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return false;
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}
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bh = qemu_bh_new(restart_listener_bh, server);
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/* zero out unspecified fields */
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*server = (VuServer) {
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.listener = listener,
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.restart_listener_bh = bh,
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.vu_iface = vu_iface,
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.max_queues = max_queues,
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.ctx = ctx,
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};
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qio_net_listener_set_name(server->listener, "vhost-user-backend-listener");
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qio_net_listener_set_client_func(server->listener,
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vu_accept,
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server,
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NULL);
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QTAILQ_INIT(&server->vu_fd_watches);
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return true;
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}
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