qemu

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