/* * Virtio Console and Generic Serial Port Devices * * Copyright Red Hat, Inc. 2009, 2010 * * Authors: * Amit Shah * * This work is licensed under the terms of the GNU GPL, version 2. See * the COPYING file in the top-level directory. */ #include "qemu/osdep.h" #include "sysemu/char.h" #include "qemu/error-report.h" #include "trace.h" #include "hw/virtio/virtio-serial.h" #include "qapi-event.h" #define TYPE_VIRTIO_CONSOLE_SERIAL_PORT "virtserialport" #define VIRTIO_CONSOLE(obj) \ OBJECT_CHECK(VirtConsole, (obj), TYPE_VIRTIO_CONSOLE_SERIAL_PORT) typedef struct VirtConsole { VirtIOSerialPort parent_obj; CharBackend chr; guint watch; } VirtConsole; /* * Callback function that's called from chardevs when backend becomes * writable. */ static gboolean chr_write_unblocked(GIOChannel *chan, GIOCondition cond, void *opaque) { VirtConsole *vcon = opaque; vcon->watch = 0; virtio_serial_throttle_port(VIRTIO_SERIAL_PORT(vcon), false); return FALSE; } /* Callback function that's called when the guest sends us data */ static ssize_t flush_buf(VirtIOSerialPort *port, const uint8_t *buf, ssize_t len) { VirtConsole *vcon = VIRTIO_CONSOLE(port); ssize_t ret; if (!qemu_chr_fe_get_driver(&vcon->chr)) { /* If there's no backend, we can just say we consumed all data. */ return len; } ret = qemu_chr_fe_write(&vcon->chr, buf, len); trace_virtio_console_flush_buf(port->id, len, ret); if (ret < len) { VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port); /* * Ideally we'd get a better error code than just -1, but * that's what the chardev interface gives us right now. If * we had a finer-grained message, like -EPIPE, we could close * this connection. */ if (ret < 0) ret = 0; /* XXX we should be queuing data to send later for the * console devices too rather than silently dropping * console data on EAGAIN. The Linux virtio-console * hvc driver though does sends with spinlocks held, * so if we enable throttling that'll stall the entire * guest kernel, not merely the process writing to the * console. * * While we could queue data for later write without * enabling throttling, this would result in the guest * being able to trigger arbitrary memory usage in QEMU * buffering data for later writes. * * So fixing this problem likely requires fixing the * Linux virtio-console hvc driver to not hold spinlocks * while writing, and instead merely block the process * that's writing. QEMU would then need some way to detect * if the guest had the fixed driver too, before we can * use throttling on host side. */ if (!k->is_console) { virtio_serial_throttle_port(port, true); if (!vcon->watch) { vcon->watch = qemu_chr_fe_add_watch(&vcon->chr, G_IO_OUT|G_IO_HUP, chr_write_unblocked, vcon); } } } return ret; } /* Callback function that's called when the guest opens/closes the port */ static void set_guest_connected(VirtIOSerialPort *port, int guest_connected) { VirtConsole *vcon = VIRTIO_CONSOLE(port); DeviceState *dev = DEVICE(port); VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port); if (!k->is_console) { qemu_chr_fe_set_open(&vcon->chr, guest_connected); } if (dev->id) { qapi_event_send_vserport_change(dev->id, guest_connected, &error_abort); } } static void guest_writable(VirtIOSerialPort *port) { VirtConsole *vcon = VIRTIO_CONSOLE(port); qemu_chr_fe_accept_input(&vcon->chr); } /* Readiness of the guest to accept data on a port */ static int chr_can_read(void *opaque) { VirtConsole *vcon = opaque; return virtio_serial_guest_ready(VIRTIO_SERIAL_PORT(vcon)); } /* Send data from a char device over to the guest */ static void chr_read(void *opaque, const uint8_t *buf, int size) { VirtConsole *vcon = opaque; VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon); trace_virtio_console_chr_read(port->id, size); virtio_serial_write(port, buf, size); } static void chr_event(void *opaque, int event) { VirtConsole *vcon = opaque; VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon); trace_virtio_console_chr_event(port->id, event); switch (event) { case CHR_EVENT_OPENED: virtio_serial_open(port); break; case CHR_EVENT_CLOSED: if (vcon->watch) { g_source_remove(vcon->watch); vcon->watch = 0; } virtio_serial_close(port); break; } } static void virtconsole_realize(DeviceState *dev, Error **errp) { VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(dev); VirtConsole *vcon = VIRTIO_CONSOLE(dev); VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(dev); CharDriverState *chr = qemu_chr_fe_get_driver(&vcon->chr); if (port->id == 0 && !k->is_console) { error_setg(errp, "Port number 0 on virtio-serial devices reserved " "for virtconsole devices for backward compatibility."); return; } if (chr) { /* * For consoles we don't block guest data transfer just * because nothing is connected - we'll just let it go * whetherever the chardev wants - /dev/null probably. * * For serial ports we need 100% reliable data transfer * so we use the opened/closed signals from chardev to * trigger open/close of the device */ if (k->is_console) { qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read, NULL, vcon, NULL, true); virtio_serial_open(port); } else { qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read, chr_event, vcon, NULL, false); } } } static void virtconsole_unrealize(DeviceState *dev, Error **errp) { VirtConsole *vcon = VIRTIO_CONSOLE(dev); if (vcon->watch) { g_source_remove(vcon->watch); } } static void virtconsole_class_init(ObjectClass *klass, void *data) { VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_CLASS(klass); k->is_console = true; } static const TypeInfo virtconsole_info = { .name = "virtconsole", .parent = TYPE_VIRTIO_CONSOLE_SERIAL_PORT, .class_init = virtconsole_class_init, }; static Property virtserialport_properties[] = { DEFINE_PROP_CHR("chardev", VirtConsole, chr), DEFINE_PROP_END_OF_LIST(), }; static void virtserialport_class_init(ObjectClass *klass, void *data) { DeviceClass *dc = DEVICE_CLASS(klass); VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_CLASS(klass); k->realize = virtconsole_realize; k->unrealize = virtconsole_unrealize; k->have_data = flush_buf; k->set_guest_connected = set_guest_connected; k->guest_writable = guest_writable; dc->props = virtserialport_properties; } static const TypeInfo virtserialport_info = { .name = TYPE_VIRTIO_CONSOLE_SERIAL_PORT, .parent = TYPE_VIRTIO_SERIAL_PORT, .instance_size = sizeof(VirtConsole), .class_init = virtserialport_class_init, }; static void virtconsole_register_types(void) { type_register_static(&virtserialport_info); type_register_static(&virtconsole_info); } type_init(virtconsole_register_types)