+See @ref{direct_linux_boot} to have an example of network use with a
+Linux distribution and @ref{sec_invocation} to have examples of
+command lines using the TAP network interfaces.
+
+@subsection Using the user mode network stack
+
+By using the option @option{-net user} (default configuration if no
+@option{-net} option is specified), QEMU uses a completely user mode
+network stack (you don't need root priviledge to use the virtual
+network). The virtual network configuration is the following:
+
+@example
+
+ QEMU VLAN <------> Firewall/DHCP server <-----> Internet
+ | (10.0.2.2)
+ |
+ ----> DNS server (10.0.2.3)
+ |
+ ----> SMB server (10.0.2.4)
+@end example
+
+The QEMU VM behaves as if it was behind a firewall which blocks all
+incoming connections. You can use a DHCP client to automatically
+configure the network in the QEMU VM. The DHCP server assign addresses
+to the hosts starting from 10.0.2.15.
+
+In order to check that the user mode network is working, you can ping
+the address 10.0.2.2 and verify that you got an address in the range
+10.0.2.x from the QEMU virtual DHCP server.
+
+Note that @code{ping} is not supported reliably to the internet as it
+would require root priviledges. It means you can only ping the local
+router (10.0.2.2).
+
+When using the built-in TFTP server, the router is also the TFTP
+server.
+
+When using the @option{-redir} option, TCP or UDP connections can be
+redirected from the host to the guest. It allows for example to
+redirect X11, telnet or SSH connections.
+
+@subsection Connecting VLANs between QEMU instances
+
+Using the @option{-net socket} option, it is possible to make VLANs
+that span several QEMU instances. See @ref{sec_invocation} to have a
+basic example.
+
+@node direct_linux_boot
+@section Direct Linux Boot
+
+This section explains how to launch a Linux kernel inside QEMU without
+having to make a full bootable image. It is very useful for fast Linux
+kernel testing. The QEMU network configuration is also explained.
+
+@enumerate
+@item
+Download the archive @file{linux-test-xxx.tar.gz} containing a Linux
+kernel and a disk image.
+
+@item Optional: If you want network support (for example to launch X11 examples), you
+must copy the script @file{qemu-ifup} in @file{/etc} and configure
+properly @code{sudo} so that the command @code{ifconfig} contained in
+@file{qemu-ifup} can be executed as root. You must verify that your host
+kernel supports the TUN/TAP network interfaces: the device
+@file{/dev/net/tun} must be present.
+
+When network is enabled, there is a virtual network connection between
+the host kernel and the emulated kernel. The emulated kernel is seen
+from the host kernel at IP address 172.20.0.2 and the host kernel is
+seen from the emulated kernel at IP address 172.20.0.1.
+
+@item Launch @code{qemu.sh}. You should have the following output:
+
+@example
+> ./qemu.sh
+Connected to host network interface: tun0
+Linux version 2.4.21 (bellard@voyager.localdomain) (gcc version 3.2.2 20030222 (Red Hat Linux 3.2.2-5)) #5 Tue Nov 11 18:18:53 CET 2003
+BIOS-provided physical RAM map:
+ BIOS-e801: 0000000000000000 - 000000000009f000 (usable)
+ BIOS-e801: 0000000000100000 - 0000000002000000 (usable)
+32MB LOWMEM available.
+On node 0 totalpages: 8192
+zone(0): 4096 pages.
+zone(1): 4096 pages.
+zone(2): 0 pages.
+Kernel command line: root=/dev/hda sb=0x220,5,1,5 ide2=noprobe ide3=noprobe ide4=noprobe ide5=noprobe console=ttyS0
+ide_setup: ide2=noprobe
+ide_setup: ide3=noprobe
+ide_setup: ide4=noprobe
+ide_setup: ide5=noprobe
+Initializing CPU#0
+Detected 2399.621 MHz processor.
+Console: colour EGA 80x25
+Calibrating delay loop... 4744.80 BogoMIPS
+Memory: 28872k/32768k available (1210k kernel code, 3508k reserved, 266k data, 64k init, 0k highmem)
+Dentry cache hash table entries: 4096 (order: 3, 32768 bytes)
+Inode cache hash table entries: 2048 (order: 2, 16384 bytes)
+Mount cache hash table entries: 512 (order: 0, 4096 bytes)
+Buffer-cache hash table entries: 1024 (order: 0, 4096 bytes)
+Page-cache hash table entries: 8192 (order: 3, 32768 bytes)
+CPU: Intel Pentium Pro stepping 03
+Checking 'hlt' instruction... OK.
+POSIX conformance testing by UNIFIX
+Linux NET4.0 for Linux 2.4
+Based upon Swansea University Computer Society NET3.039
+Initializing RT netlink socket
+apm: BIOS not found.
+Starting kswapd
+Journalled Block Device driver loaded
+Detected PS/2 Mouse Port.
+pty: 256 Unix98 ptys configured
+Serial driver version 5.05c (2001-07-08) with no serial options enabled
+ttyS00 at 0x03f8 (irq = 4) is a 16450
+ne.c:v1.10 9/23/94 Donald Becker (becker@scyld.com)
+Last modified Nov 1, 2000 by Paul Gortmaker
+NE*000 ethercard probe at 0x300: 52 54 00 12 34 56
+eth0: NE2000 found at 0x300, using IRQ 9.
+RAMDISK driver initialized: 16 RAM disks of 4096K size 1024 blocksize
+Uniform Multi-Platform E-IDE driver Revision: 7.00beta4-2.4
+ide: Assuming 50MHz system bus speed for PIO modes; override with idebus=xx
+hda: QEMU HARDDISK, ATA DISK drive
+ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
+hda: attached ide-disk driver.
+hda: 20480 sectors (10 MB) w/256KiB Cache, CHS=20/16/63
+Partition check:
+ hda:
+Soundblaster audio driver Copyright (C) by Hannu Savolainen 1993-1996
+NET4: Linux TCP/IP 1.0 for NET4.0
+IP Protocols: ICMP, UDP, TCP, IGMP
+IP: routing cache hash table of 512 buckets, 4Kbytes
+TCP: Hash tables configured (established 2048 bind 4096)
+NET4: Unix domain sockets 1.0/SMP for Linux NET4.0.
+EXT2-fs warning: mounting unchecked fs, running e2fsck is recommended
+VFS: Mounted root (ext2 filesystem).
+Freeing unused kernel memory: 64k freed
+
+Linux version 2.4.21 (bellard@voyager.localdomain) (gcc version 3.2.2 20030222 (Red Hat Linux 3.2.2-5)) #5 Tue Nov 11 18:18:53 CET 2003
+
+QEMU Linux test distribution (based on Redhat 9)
+
+Type 'exit' to halt the system
+
+sh-2.05b#
+@end example
+
+@item
+Then you can play with the kernel inside the virtual serial console. You
+can launch @code{ls} for example. Type @key{Ctrl-a h} to have an help
+about the keys you can type inside the virtual serial console. In
+particular, use @key{Ctrl-a x} to exit QEMU and use @key{Ctrl-a b} as
+the Magic SysRq key.
+
+@item
+If the network is enabled, launch the script @file{/etc/linuxrc} in the
+emulator (don't forget the leading dot):
+@example
+. /etc/linuxrc
+@end example
+
+Then enable X11 connections on your PC from the emulated Linux:
+@example
+xhost +172.20.0.2
+@end example
+
+You can now launch @file{xterm} or @file{xlogo} and verify that you have
+a real Virtual Linux system !
+
+@end enumerate
+
+NOTES:
+@enumerate
+@item
+A 2.5.74 kernel is also included in the archive. Just
+replace the bzImage in qemu.sh to try it.
+
+@item
+In order to exit cleanly from qemu, you can do a @emph{shutdown} inside
+qemu. qemu will automatically exit when the Linux shutdown is done.
+
+@item
+You can boot slightly faster by disabling the probe of non present IDE
+interfaces. To do so, add the following options on the kernel command
+line:
+@example
+ide1=noprobe ide2=noprobe ide3=noprobe ide4=noprobe ide5=noprobe
+@end example
+
+@item
+The example disk image is a modified version of the one made by Kevin
+Lawton for the plex86 Project (@url{www.plex86.org}).
+
+@end enumerate
+
+@section USB emulation
+
+QEMU emulates a PCI UHCI USB controller and a 8 port USB hub connected
+to it. You can virtually plug to the hub virtual USB devices or real
+host USB devices (experimental, works only on Linux hosts).
+
+@subsection Using virtual USB devices
+
+A virtual USB mouse device is available for testing in QEMU.
+
+You can try it with the following monitor commands:
+
+@example
+# add the mouse device
+(qemu) usb_add mouse
+
+# show the virtual USB devices plugged on the QEMU Virtual USB hub
+(qemu) info usb
+ Device 0.3, speed 12 Mb/s
+
+# after some time you can try to remove the mouse
+(qemu) usb_del 0.3
+@end example
+
+The option @option{-usbdevice} is similar to the monitor command
+@code{usb_add}.
+
+@subsection Using host USB devices on a Linux host
+
+WARNING: this is an experimental feature. QEMU will slow down when
+using it. USB devices requiring real time streaming (i.e. USB Video
+Cameras) are not supported yet.
+
+@enumerate
+@item If you use an early Linux 2.4 kernel, verify that no Linux driver
+is actually using the USB device. A simple way to do that is simply to
+disable the corresponding kernel module by renaming it from @file{mydriver.o}
+to @file{mydriver.o.disabled}.
+
+@item Verify that @file{/proc/bus/usb} is working (most Linux distributions should enable it by default). You should see something like that:
+@example
+ls /proc/bus/usb
+001 devices drivers
+@end example
+
+@item Since only root can access to the USB devices directly, you can either launch QEMU as root or change the permissions of the USB devices you want to use. For testing, the following suffices:
+@example
+chown -R myuid /proc/bus/usb
+@end example
+
+@item Launch QEMU and do in the monitor:
+@example
+info usbhost
+ Device 1.2, speed 480 Mb/s
+ Class 00: USB device 1234:5678, USB DISK
+@end example
+You should see the list of the devices you can use (Never try to use
+hubs, it won't work).
+
+@item Add the device in QEMU by using:
+@example
+usb_add host:1234:5678
+@end example
+
+Normally the guest OS should report that a new USB device is
+plugged. You can use the option @option{-usbdevice} to do the same.
+
+@item Now you can try to use the host USB device in QEMU.
+
+@end enumerate
+
+When relaunching QEMU, you may have to unplug and plug again the USB
+device to make it work again (this is a bug).
+
+@node gdb_usage
+@section GDB usage
+
+QEMU has a primitive support to work with gdb, so that you can do
+'Ctrl-C' while the virtual machine is running and inspect its state.
+
+In order to use gdb, launch qemu with the '-s' option. It will wait for a
+gdb connection:
+@example
+> qemu -s -kernel arch/i386/boot/bzImage -hda root-2.4.20.img -append "root=/dev/hda"
+Connected to host network interface: tun0
+Waiting gdb connection on port 1234
+@end example
+
+Then launch gdb on the 'vmlinux' executable:
+@example
+> gdb vmlinux
+@end example
+
+In gdb, connect to QEMU:
+@example
+(gdb) target remote localhost:1234
+@end example
+
+Then you can use gdb normally. For example, type 'c' to launch the kernel:
+@example
+(gdb) c
+@end example
+
+Here are some useful tips in order to use gdb on system code:
+
+@enumerate
+@item
+Use @code{info reg} to display all the CPU registers.
+@item
+Use @code{x/10i $eip} to display the code at the PC position.
+@item
+Use @code{set architecture i8086} to dump 16 bit code. Then use
+@code{x/10i $cs*16+*eip} to dump the code at the PC position.
+@end enumerate
+
+@section Target OS specific information
+
+@subsection Linux
+
+To have access to SVGA graphic modes under X11, use the @code{vesa} or
+the @code{cirrus} X11 driver. For optimal performances, use 16 bit
+color depth in the guest and the host OS.
+
+When using a 2.6 guest Linux kernel, you should add the option
+@code{clock=pit} on the kernel command line because the 2.6 Linux
+kernels make very strict real time clock checks by default that QEMU
+cannot simulate exactly.
+
+When using a 2.6 guest Linux kernel, verify that the 4G/4G patch is
+not activated because QEMU is slower with this patch. The QEMU
+Accelerator Module is also much slower in this case. Earlier Fedora
+Core 3 Linux kernel (< 2.6.9-1.724_FC3) were known to incorporte this
+patch by default. Newer kernels don't have it.
+
+@subsection Windows
+
+If you have a slow host, using Windows 95 is better as it gives the
+best speed. Windows 2000 is also a good choice.
+
+@subsubsection SVGA graphic modes support
+
+QEMU emulates a Cirrus Logic GD5446 Video
+card. All Windows versions starting from Windows 95 should recognize
+and use this graphic card. For optimal performances, use 16 bit color
+depth in the guest and the host OS.
+
+@subsubsection CPU usage reduction
+
+Windows 9x does not correctly use the CPU HLT
+instruction. The result is that it takes host CPU cycles even when
+idle. You can install the utility from
+@url{http://www.user.cityline.ru/~maxamn/amnhltm.zip} to solve this
+problem. Note that no such tool is needed for NT, 2000 or XP.
+
+@subsubsection Windows 2000 disk full problem
+
+Windows 2000 has a bug which gives a disk full problem during its
+installation. When installing it, use the @option{-win2k-hack} QEMU
+option to enable a specific workaround. After Windows 2000 is
+installed, you no longer need this option (this option slows down the
+IDE transfers).
+
+@subsubsection Windows 2000 shutdown
+
+Windows 2000 cannot automatically shutdown in QEMU although Windows 98
+can. It comes from the fact that Windows 2000 does not automatically
+use the APM driver provided by the BIOS.
+
+In order to correct that, do the following (thanks to Struan
+Bartlett): go to the Control Panel => Add/Remove Hardware & Next =>
+Add/Troubleshoot a device => Add a new device & Next => No, select the
+hardware from a list & Next => NT Apm/Legacy Support & Next => Next
+(again) a few times. Now the driver is installed and Windows 2000 now
+correctly instructs QEMU to shutdown at the appropriate moment.
+
+@subsubsection Share a directory between Unix and Windows
+
+See @ref{sec_invocation} about the help of the option @option{-smb}.
+
+@subsubsection Windows XP security problems
+
+Some releases of Windows XP install correctly but give a security
+error when booting:
+@example
+A problem is preventing Windows from accurately checking the
+license for this computer. Error code: 0x800703e6.
+@end example
+The only known workaround is to boot in Safe mode
+without networking support.
+
+Future QEMU releases are likely to correct this bug.
+
+@subsection MS-DOS and FreeDOS
+
+@subsubsection CPU usage reduction
+
+DOS does not correctly use the CPU HLT instruction. The result is that
+it takes host CPU cycles even when idle. You can install the utility
+from @url{http://www.vmware.com/software/dosidle210.zip} to solve this
+problem.
+
+@chapter QEMU System emulator for non PC targets
+
+QEMU is a generic emulator and it emulates many non PC
+machines. Most of the options are similar to the PC emulator. The
+differences are mentionned in the following sections.
+
+@section QEMU PowerPC System emulator
+
+Use the executable @file{qemu-system-ppc} to simulate a complete PREP
+or PowerMac PowerPC system.
+
+QEMU emulates the following PowerMac peripherals:
+
+@itemize @minus
+@item
+UniNorth PCI Bridge
+@item
+PCI VGA compatible card with VESA Bochs Extensions
+@item
+2 PMAC IDE interfaces with hard disk and CD-ROM support
+@item
+NE2000 PCI adapters
+@item
+Non Volatile RAM
+@item
+VIA-CUDA with ADB keyboard and mouse.