Re: Redesign of QEMU startup & initial configuration

[Paolo Bonzini]

On 12/10/21 14:54, Markus Armbruster wrote:
> I want an open path to a single binary.  Taking years to get there is
> fine.

The single binary is a distraction in my opinion.  Imagine
instead of vl.c you have this in your second binary:

/*
 * This copyright line means that at some point the below actually compiled
 * in my tree (though it was only a stub); I am not fully making it up.
 *
 * Copyright (c) 2020 Red Hat, Inc.
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

#include "qemu/osdep.h"
#include "qemu/rcu.h"
#include "qemu-common.h"
#include "chardev/char.h"
#include "monitor/monitor.h"
#include "qapi/error.h"
#include "qapi/qapi-commands-misc.h"
#include "qapi/qapi-commands-ui.h"
#include "qemu/systemd.h"
#include "sysemu/cpu-timers.h"
#include "sysemu/sysemu.h"
#include "ui/console.h"
#include "hw/qdev-core.h"

static void open_socket_and_monitor(void)
{
    int nfds = check_socket_activation();
    Chardev *chardev;
    if (nfds > 1) {
        error_report("QEMU only supports listening on one socket");
        exit(1);
    }
    if (!nfds) {
        ChardevBackend backend = {
            .type = CHARDEV_BACKEND_KIND_STDIO,
            .u.stdio.data = &(ChardevStdio) {
                .has_signal = true,
                .signal = false
            }
        };
        chardev = qemu_chardev_new("#qmp0", TYPE_CHARDEV_STDIO, &backend, NULL, 
&error_fatal);
    } else {
        ChardevBackend backend = {
           .type = CHARDEV_BACKEND_KIND_SOCKET,
           .u.socket.data = &(ChardevSocket) {
               .addr = &(SocketAddressLegacy) {
                   .type = SOCKET_ADDRESS_LEGACY_KIND_FD,
                   .u.fd.data = &(String){
                       .str = (char *) stringify(FIRST_SOCKET_ACTIVATION_FD)
                   }
               }
           }
        };
        chardev = qemu_chardev_new("#qmp0", TYPE_CHARDEV_SOCKET, &backend, NULL, 
&error_fatal);
    }
    monitor_init_qmp(chardev, true, &error_fatal);
}

void qemu_init(int argc, char **argv, char **envp)
{
    error_init(argv[0]);
    qemu_init_exec_dir(argv[0]);
    qemu_init_subsystems();

    /* Missing: parse -name, -sandbox, -trace, -L */

    loc_set_none();
    rcu_disable_atfork();
    qemu_init_main_loop(&error_fatal);
    cpu_timers_init();
    open_socket_and_monitor();
    init_displaystate();
    os_setup_signal_handling();
}

This is the ultimate QEMU startup code.  If we can get this code to
actually build a machine, you've reached the point where you don't care
about what is in the command line parser; and consequently you don't care
if there is one binary or two.

Paolo