\input texinfo @c -*- texinfo -*-
+@iftex
@settitle QEMU CPU Emulator Reference Documentation
@titlepage
@sp 7
@center @titlefont{QEMU CPU Emulator Reference Documentation}
@sp 3
@end titlepage
+@end iftex
@chapter Introduction
@section Features
-QEMU is a FAST! processor emulator. Its purpose is to run Linux executables
-compiled for one architecture on another. For example, x86 Linux
-processes can be ran on PowerPC Linux architectures. By using dynamic
-translation it achieves a reasonnable speed while being easy to port on
-new host CPUs. Its main goal is to be able to launch the @code{Wine}
-Windows API emulator (@url{http://www.winehq.org}) or @code{DOSEMU}
-(@url{http://www.dosemu.org}) on non-x86 CPUs.
+QEMU is a FAST! processor emulator. By using dynamic translation it
+achieves a reasonnable speed while being easy to port on new host
+CPUs.
+
+QEMU has two operating modes:
+
+@itemize @minus
+
+@item
+User mode emulation. In this mode, QEMU can launch Linux processes
+compiled for one CPU on another CPU. Linux system calls are converted
+because of endianness and 32/64 bit mismatches. The Wine Windows API
+emulator (@url{http://www.winehq.org}) and the DOSEMU DOS emulator
+(@url{www.dosemu.org}) are the main targets for QEMU.
+
+@item
+Full system emulation. In this mode, QEMU emulates a full
+system, including a processor and various peripherials. Currently, it
+is only used to launch an x86 Linux kernel on an x86 Linux system. It
+enables easier testing and debugging of system code. It can also be
+used to provide virtual hosting of several virtual PCs on a single
+server.
+
+@end itemize
+
+As QEMU requires no host kernel patches to run, it is very safe and
+easy to use.
QEMU generic features:
@itemize
-@item User space only emulation.
+@item User space only or full system emulation.
+
+@item Using dynamic translation to native code for reasonnable speed.
@item Working on x86 and PowerPC hosts. Being tested on ARM, Sparc32, Alpha and S390.
-@item Using dynamic translation to native code for reasonnable speed.
+@item Self-modifying code support.
+
+@item Precise exceptions support.
+@item The virtual CPU is a library (@code{libqemu}) which can be used
+in other projects.
+
+@end itemize
+
+QEMU user mode emulation features:
+@itemize
@item Generic Linux system call converter, including most ioctls.
@item clone() emulation using native CPU clone() to use Linux scheduler for threads.
@item Accurate signal handling by remapping host signals to target signals.
+@end itemize
+@end itemize
-@item Self-modifying code support.
-
-@item The virtual CPU is a library (@code{libqemu}) which can be used
-in other projects.
-
+QEMU full system emulation features:
+@itemize
+@item Using mmap() system calls to simulate the MMU
@end itemize
@section x86 emulation
@itemize
@item The virtual x86 CPU supports 16 bit and 32 bit addressing with segmentation.
-User space LDT and GDT are emulated. VM86 mode is also supported to run DOSEMU.
+LDT/GDT and IDT are emulated. VM86 mode is also supported to run DOSEMU.
-@item Precise user space x86 exceptions.
-
-@item Support of host page sizes bigger than 4KB.
+@item Support of host page sizes bigger than 4KB in user mode emulation.
@item QEMU can emulate itself on x86.
@item IPC syscalls are missing.
@item The x86 segment limits and access rights are not tested at every
-memory access (and will never be to have good performances).
+memory access.
@item On non x86 host CPUs, @code{double}s are used instead of the non standard
10 byte @code{long double}s of x86 for floating point emulation to get
maximum performances.
+@item Full system emulation only works if no data are mapped above the virtual address
+0xc0000000 (yet).
+
+@item Some priviledged instructions or behaviors are missing. Only the ones
+needed for proper Linux kernel operation are emulated.
+
+@item No memory separation between the kernel and the user processes is done.
+It will be implemented very soon.
+
@end itemize
@section ARM emulation
@end itemize
-@chapter Invocation
+@section SPARC emulation
+
+The SPARC emulation is currently in development.
+
+@chapter QEMU User space emulator invocation
@section Quick Start
libraries:
@example
-qemu -L / /bin/ls
+qemu-i386 -L / /bin/ls
@end example
@code{-L /} tells that the x86 dynamic linker must be searched with a
@item Since QEMU is also a linux process, you can launch qemu with qemu:
@example
-qemu -L / qemu -L / /bin/ls
+qemu-i386 -L / qemu-i386 -L / /bin/ls
@end example
@item On non x86 CPUs, you need first to download at least an x86 glibc
Then you can launch the precompiled @file{ls} x86 executable:
@example
-qemu /usr/local/qemu-i386/bin/ls-i386
+qemu-i386 /usr/local/qemu-i386/bin/ls-i386
@end example
You can look at @file{/usr/local/qemu-i386/bin/qemu-conf.sh} so that
QEMU is automatically launched by the Linux kernel when you try to
@item The x86 version of QEMU is also included. You can try weird things such as:
@example
-qemu /usr/local/qemu-i386/bin/qemu-i386 /usr/local/qemu-i386/bin/ls-i386
+qemu-i386 /usr/local/qemu-i386/bin/qemu-i386 /usr/local/qemu-i386/bin/ls-i386
@end example
@end itemize
able to do:
@example
-qemu /usr/local/qemu-i386/bin/ls-i386
+qemu-i386 /usr/local/qemu-i386/bin/ls-i386
@end example
@item Download the binary x86 Wine install
@item Then you can try the example @file{putty.exe}:
@example
-qemu /usr/local/qemu-i386/wine/bin/wine /usr/local/qemu-i386/wine/c/Program\ Files/putty.exe
+qemu-i386 /usr/local/qemu-i386/wine/bin/wine /usr/local/qemu-i386/wine/c/Program\ Files/putty.exe
@end example
@end itemize
@section Command line options
@example
-usage: qemu [-h] [-d] [-L path] [-s size] program [arguments...]
+usage: qemu-i386 [-h] [-d] [-L path] [-s size] program [arguments...]
@end example
@table @option
Act as if the host page size was 'pagesize' bytes
@end table
+@chapter QEMU System emulator invocation
+
+@section Introduction
+
+@c man begin DESCRIPTION
+
+The QEMU System emulator simulates a complete PC. It can either boot
+directly a Linux kernel (without any BIOS or boot loader) or boot like a
+real PC with the included BIOS.
+
+In order to meet specific user needs, two versions of QEMU are
+available:
+
+@enumerate
+
+@item
+@code{qemu} uses the host Memory Management Unit (MMU) to simulate
+the x86 MMU. It is @emph{fast} but has limitations because the whole 4 GB
+address space cannot be used and some memory mapped peripherials
+cannot be emulated accurately yet. Therefore, a specific Linux kernel
+must be used (@xref{linux_compile}).
+
+@item
+@code{qemu-softmmu} uses a software MMU. It is about @emph{two times
+slower} but gives a more accurate emulation. (XXX: Linux cannot be ran
+unpatched yet).
+
+@end enumerate
+
+QEMU emulates the following PC peripherials:
+
+@itemize @minus
+@item
+VGA (hardware level, including all non standard modes)
+@item
+PS/2 mouse and keyboard
+@item
+IDE disk interface (port=0x1f0, irq=14)
+@item
+NE2000 network adapter (port=0x300, irq=9)
+@item
+Serial port (port=0x3f8, irq=4)
+@item
+PIC (interrupt controler)
+@item
+PIT (timers)
+@item
+CMOS memory
+@end itemize
+
+@c man end
+
+@section Quick Start
+
+Download the linux image (@file{linux.img}) and type:
+
+@example
+qemu-softmmu linux.img
+@end example
+
+Linux should boot and give you a prompt.
+
+@section Direct Linux Boot and Network emulation
+
+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
+Uncompressing Linux... Ok, booting the kernel.
+Linux version 2.4.20 (fabrice@localhost.localdomain) (gcc version 2.96 20000731 (Red Hat Linux 7.3 2.96-110)) #22 lun jui 7 13:37:41 CEST 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 ide1=noprobe ide2=noprobe ide3=noprobe ide4=noprobe ide5=noprobe
+ide_setup: ide1=noprobe
+ide_setup: ide2=noprobe
+ide_setup: ide3=noprobe
+ide_setup: ide4=noprobe
+ide_setup: ide5=noprobe
+Initializing CPU#0
+Detected 501.285 MHz processor.
+Calibrating delay loop... 989.59 BogoMIPS
+Memory: 29268k/32768k available (907k kernel code, 3112k reserved, 212k data, 52k 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
+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
+Uniform Multi-Platform E-IDE driver Revision: 6.31
+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: 12288 sectors (6 MB) w/256KiB Cache, CHS=12/16/63
+Partition check:
+ hda: unknown partition table
+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
+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: 52k freed
+sh: can't access tty; job control turned off
+#
+@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
+vl creates a temporary file in @var{$QEMU_TMPDIR} (@file{/tmp} is the
+default) containing all the simulated PC memory. If possible, try to use
+a temporary directory using the tmpfs filesystem to avoid too many
+unnecessary disk accesses.
+
+@item
+In order to exit cleanly for vl, you can do a @emph{shutdown} inside
+vl. vl 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 Invocation
+
+@example
+@c man begin SYNOPSIS
+usage: qemu [options] [disk_image]
+@c man end
+@end example
+
+@c man begin OPTIONS
+@var{disk_image} is a raw hard image image for IDE hard disk 0.
+
+General options:
+@table @option
+@item -hda file
+@item -hdb file
+Use @var{file} as hard disk 0 or 1 image (@xref{disk_images}).
+
+@item -snapshot
+
+Write to temporary files instead of disk image files. In this case,
+the raw disk image you use is not written back. You can however force
+the write back by pressing @key{C-a s} (@xref{disk_images}).
+
+@item -m megs
+Set virtual RAM size to @var{megs} megabytes.
+
+@item -n script
+Set network init script [default=/etc/vl-ifup]. This script is
+launched to configure the host network interface (usually tun0)
+corresponding to the virtual NE2000 card.
+
+@item -initrd file
+Use @var{file} as initial ram disk.
+
+@item -tun-fd fd
+Assumes @var{fd} talks to tap/tun and use it. Read
+@url{http://bellard.org/qemu/tetrinet.html} to have an example of its
+use.
+
+@item -nographic
+
+Normally, QEMU uses SDL to display the VGA output. With this option,
+you can totally disable graphical output so that QEMU is a simple
+command line application. The emulated serial port is redirected on
+the console. Therefore, you can still use QEMU to debug a Linux kernel
+with a serial console.
+
+@end table
+
+Linux boot specific (does not require a full PC boot with a BIOS):
+@table @option
+
+@item -kernel bzImage
+Use @var{bzImage} as kernel image.
+
+@item -append cmdline
+Use @var{cmdline} as kernel command line
+
+@item -initrd file
+Use @var{file} as initial ram disk.
+
+@end table
+
+Debug options:
+@table @option
+@item -s
+Wait gdb connection to port 1234 (@xref{gdb_usage}).
+@item -p port
+Change gdb connection port.
+@item -d
+Output log in /tmp/vl.log
+@end table
+
+During emulation, use @key{C-a h} to get terminal commands:
+
+@table @key
+@item C-a h
+Print this help
+@item C-a x
+Exit emulatior
+@item C-a s
+Save disk data back to file (if -snapshot)
+@item C-a b
+Send break (magic sysrq)
+@item C-a C-a
+Send C-a
+@end table
+@c man end
+
+@ignore
+
+@setfilename qemu
+@settitle QEMU System Emulator
+
+@c man begin SEEALSO
+The HTML documentation of QEMU for more precise information and Linux
+user mode emulator invocation.
+@c man end
+
+@c man begin AUTHOR
+Fabrice Bellard
+@c man end
+
+@end ignore
+
+@end ignore
+@node disk_images
+@section Disk Images
+
+@subsection Raw disk images
+
+The disk images can simply be raw images of the hard disk. You can
+create them with the command:
+@example
+dd if=/dev/zero of=myimage bs=1024 count=mysize
+@end example
+where @var{myimage} is the image filename and @var{mysize} is its size
+in kilobytes.
+
+@subsection Snapshot mode
+
+If you use the option @option{-snapshot}, all disk images are
+considered as read only. When sectors in written, they are written in
+a temporary file created in @file{/tmp}. You can however force the
+write back to the raw disk images by pressing @key{C-a s}.
+
+NOTE: The snapshot mode only works with raw disk images.
+
+@subsection Copy On Write disk images
+
+QEMU also supports user mode Linux
+(@url{http://user-mode-linux.sourceforge.net/}) Copy On Write (COW)
+disk images. The COW disk images are much smaller than normal images
+as they store only modified sectors. They also permit the use of the
+same disk image template for many users.
+
+To create a COW disk images, use the command:
+
+@example
+qemu-mkcow -f myrawimage.bin mycowimage.cow
+@end example
+
+@file{myrawimage.bin} is a raw image you want to use as original disk
+image. It will never be written to.
+
+@file{mycowimage.cow} is the COW disk image which is created by
+@code{qemu-mkcow}. You can use it directly with the @option{-hdx}
+options. You must not modify the original raw disk image if you use
+COW images, as COW images only store the modified sectors from the raw
+disk image. QEMU stores the original raw disk image name and its
+modified time in the COW disk image so that chances of mistakes are
+reduced.
+
+If the raw disk image is not read-only, by pressing @key{C-a s} you
+can flush the COW disk image back into the raw disk image, as in
+snapshot mode.
+
+COW disk images can also be created without a corresponding raw disk
+image. It is useful to have a big initial virtual disk image without
+using much disk space. Use:
+
+@example
+qemu-mkcow mycowimage.cow 1024
+@end example
+
+to create a 1 gigabyte empty COW disk image.
+
+NOTES:
+@enumerate
+@item
+COW disk images must be created on file systems supporting
+@emph{holes} such as ext2 or ext3.
+@item
+Since holes are used, the displayed size of the COW disk image is not
+the real one. To know it, use the @code{ls -ls} command.
+@end enumerate
+
+@node linux_compile
+@section Linux Kernel Compilation
+
+You should be able to use any kernel with QEMU provided you make the
+following changes (only 2.4.x and 2.5.x were tested):
+
+@enumerate
+@item
+The kernel must be mapped at 0x90000000 (the default is
+0xc0000000). You must modify only two lines in the kernel source:
+
+In @file{include/asm/page.h}, replace
+@example
+#define __PAGE_OFFSET (0xc0000000)
+@end example
+by
+@example
+#define __PAGE_OFFSET (0x90000000)
+@end example
+
+And in @file{arch/i386/vmlinux.lds}, replace
+@example
+ . = 0xc0000000 + 0x100000;
+@end example
+by
+@example
+ . = 0x90000000 + 0x100000;
+@end example
+
+@item
+If you want to enable SMP (Symmetric Multi-Processing) support, you
+must make the following change in @file{include/asm/fixmap.h}. Replace
+@example
+#define FIXADDR_TOP (0xffffX000UL)
+@end example
+by
+@example
+#define FIXADDR_TOP (0xa7ffX000UL)
+@end example
+(X is 'e' or 'f' depending on the kernel version). Although you can
+use an SMP kernel with QEMU, it only supports one CPU.
+
+@item
+If you are not using a 2.5 kernel as host kernel but if you use a target
+2.5 kernel, you must also ensure that the 'HZ' define is set to 100
+(1000 is the default) as QEMU cannot currently emulate timers at
+frequencies greater than 100 Hz on host Linux systems < 2.5. In
+@file{include/asm/param.h}, replace:
+
+@example
+# define HZ 1000 /* Internal kernel timer frequency */
+@end example
+by
+@example
+# define HZ 100 /* Internal kernel timer frequency */
+@end example
+
+@end enumerate
+
+The file config-2.x.x gives the configuration of the example kernels.
+
+Just type
+@example
+make bzImage
+@end example
+
+As you would do to make a real kernel. Then you can use with QEMU
+exactly the same kernel as you would boot on your PC (in
+@file{arch/i386/boot/bzImage}).
+
+@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 vl with the '-s' option. It will wait for a
+gdb connection:
+@example
+> vl -s arch/i386/boot/bzImage -hda root-2.4.20.img 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 locahost:1234
+@end example
+
+Then you can use gdb normally. For example, type 'c' to launch the kernel:
+@example
+(gdb) c
+@end example
+
+WARNING: breakpoints and single stepping are not yet supported.
+
+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
+
@chapter QEMU Internals
@section QEMU compared to other emulators
-Unlike bochs [3], QEMU emulates only a user space x86 CPU. It means that
-you cannot launch an operating system with it. The benefit is that it is
-simpler and faster due to the fact that some of the low level CPU state
-can be ignored (in particular, no virtual memory needs to be emulated).
+Like bochs [3], QEMU emulates an x86 CPU. But QEMU is much faster than
+bochs as it uses dynamic compilation and because it uses the host MMU to
+simulate the x86 MMU. The downside is that currently the emulation is
+not as accurate as bochs (for example, you cannot currently run Windows
+inside QEMU).
Like Valgrind [2], QEMU does user space emulation and dynamic
translation. Valgrind is mainly a memory debugger while QEMU has no
-support for it (QEMU could be used to detect out of bound memory accesses
-as Valgrind, but it has no support to track uninitialised data as
-Valgrind does). Valgrind dynamic translator generates better code than
-QEMU (in particular it does register allocation) but it is closely tied
-to an x86 host and target.
-
-EM86 [4] is the closest project to QEMU (and QEMU still uses some of its
-code, in particular the ELF file loader). EM86 was limited to an alpha
-host and used a proprietary and slow interpreter (the interpreter part
-of the FX!32 Digital Win32 code translator [5]).
+support for it (QEMU could be used to detect out of bound memory
+accesses as Valgrind, but it has no support to track uninitialised data
+as Valgrind does). The Valgrind dynamic translator generates better code
+than QEMU (in particular it does register allocation) but it is closely
+tied to an x86 host and target and has no support for precise exceptions
+and system emulation.
+
+EM86 [4] is the closest project to user space QEMU (and QEMU still uses
+some of its code, in particular the ELF file loader). EM86 was limited
+to an alpha host and used a proprietary and slow interpreter (the
+interpreter part of the FX!32 Digital Win32 code translator [5]).
TWIN [6] is a Windows API emulator like Wine. It is less accurate than
Wine but includes a protected mode x86 interpreter to launch x86 Windows
because all the data structures and function parameters exchanged
between the API and the x86 code must be converted.
+User mode Linux [7] was the only solution before QEMU to launch a Linux
+kernel as a process while not needing any host kernel patches. However,
+user mode Linux requires heavy kernel patches while QEMU accepts
+unpatched Linux kernels. It would be interesting to compare the
+performance of the two approaches.
+
+The new Plex86 [8] PC virtualizer is done in the same spirit as the QEMU
+system emulator. It requires a patched Linux kernel to work (you cannot
+launch the same kernel on your PC), but the patches are really small. As
+it is a PC virtualizer (no emulation is done except for some priveledged
+instructions), it has the potential of being faster than QEMU. The
+downside is that a complicated (and potentially unsafe) host kernel
+patch is needed.
+
@section Portable dynamic translation
QEMU is a dynamic translator. When it first encounters a piece of code,
a linked list of every translated block contained in a given page. Other
linked lists are also maintained to undo direct block chaining.
-Althought the overhead of doing @code{mprotect()} calls is important,
+Although the overhead of doing @code{mprotect()} calls is important,
most MSDOS programs can be emulated at reasonnable speed with QEMU and
DOSEMU.
@section Self-virtualization
-QEMU was conceived so that ultimately it can emulate itself. Althought
+QEMU was conceived so that ultimately it can emulate itself. Although
it is not very useful, it is an important test to show the power of the
emulator.
shared object as the ld-linux.so ELF interpreter. That way, it can be
relocated at load time.
+@section MMU emulation
+
+For system emulation, QEMU uses the mmap() system call to emulate the
+target CPU MMU. It works as long the emulated OS does not use an area
+reserved by the host OS (such as the area above 0xc0000000 on x86
+Linux).
+
+It is planned to add a slower but more precise MMU emulation
+with a software MMU.
+
@section Bibliography
@table @asis
@url{http://www.willows.com/}, Windows API library emulation from
Willows Software.
+@item [7]
+@url{http://user-mode-linux.sourceforge.net/},
+The User-mode Linux Kernel.
+
+@item [8]
+@url{http://www.plex86.org/},
+The new Plex86 project.
+
@end table
@chapter Regression Tests
projects / qemu.git / blobdiff