@end itemize
Linux user emulator (Linux host only) can be used to launch the Wine
-Windows API emulator (@url{http://www.winehq.org}). A Darwin user
-emulator (Darwin hosts only) exists and a BSD user emulator for BSD
+Windows API emulator (@url{http://www.winehq.org}). A BSD user emulator for BSD
hosts is under development. It would also be possible to develop a
similar user emulator for Solaris.
@item Core Xtensa ISA emulation, including most options: code density,
loop, extended L32R, 16- and 32-bit multiplication, 32-bit division,
-MAC16, miscellaneous operations, boolean, multiprocessor synchronization,
+MAC16, miscellaneous operations, boolean, FP coprocessor, coprocessor
+context, debug, multiprocessor synchronization,
conditional store, exceptions, relocatable vectors, unaligned exception,
interrupts (including high priority and timer), hardware alignment,
region protection, region translation, MMU, windowed registers, thread
pointer, processor ID.
-@item Not implemented options: FP coprocessor, coprocessor context,
-data/instruction cache (including cache prefetch and locking), XLMI,
-processor interface, debug. Also options not covered by the core ISA
-(e.g. FLIX, wide branches) are not implemented.
+@item Not implemented options: data/instruction cache (including cache
+prefetch and locking), XLMI, processor interface. Also options not
+covered by the core ISA (e.g. FLIX, wide branches) are not implemented.
@item Can run most Xtensa Linux binaries.
@node QEMU compared to other emulators
@section QEMU compared to other emulators
-Like bochs [3], QEMU emulates an x86 CPU. But QEMU is much faster than
+Like bochs [1], QEMU emulates an x86 CPU. But QEMU is much faster than
bochs as it uses dynamic compilation. Bochs is closely tied to x86 PC
emulation while QEMU can emulate several processors.
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
+EM86 [3] 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]).
+interpreter part of the FX!32 Digital Win32 code translator [4]).
-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
-executables. Such an approach has greater potential because most of the
-Windows API is executed natively but it is far more difficult to develop
-because all the data structures and function parameters exchanged
+TWIN from Willows Software was a Windows API emulator like Wine. It is less
+accurate than Wine but includes a protected mode x86 interpreter to launch
+x86 Windows executables. Such an approach has greater potential because most
+of the Windows API is executed natively but it is far more difficult to
+develop 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
+User mode Linux [5] 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. The price to pay is that QEMU is
slower.
-The Plex86 [8] PC virtualizer is done in the same spirit as the now
+The Plex86 [6] PC virtualizer is done in the same spirit as the now
obsolete qemu-fast 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
being faster than QEMU. The downside is that a complicated (and
potentially unsafe) host kernel patch is needed.
-The commercial PC Virtualizers (VMWare [9], VirtualPC [10], TwoOStwo
-[11]) are faster than QEMU, but they all need specific, proprietary
+The commercial PC Virtualizers (VMWare [7], VirtualPC [8]) are faster
+than QEMU (without virtualization), but they all need specific, proprietary
and potentially unsafe host drivers. Moreover, they are unable to
provide cycle exact simulation as an emulator can.
-VirtualBox [12], Xen [13] and KVM [14] are based on QEMU. QEMU-SystemC
-[15] uses QEMU to simulate a system where some hardware devices are
+VirtualBox [9], Xen [10] and KVM [11] are based on QEMU. QEMU-SystemC
+[12] uses QEMU to simulate a system where some hardware devices are
developed in SystemC.
@node Portable dynamic translation
performed at this stage, including liveness analysis and trivial
constant expression evaluation. TCG ops are then implemented in the
host CPU back end, also known as TCG target (see
-@code{tcg/i386/tcg-target.c}). For more information, please take a
+@code{tcg/i386/tcg-target.inc.c}). For more information, please take a
look at @code{tcg/README}.
@node Condition code optimisations
@section Direct block chaining
After each translated basic block is executed, QEMU uses the simulated
-Program Counter (PC) and other cpu state informations (such as the CS
+Program Counter (PC) and other cpu state information (such as the CS
segment base value) to find the next basic block.
In order to accelerate the most common cases where the new simulated PC
@node Hardware interrupts
@section Hardware interrupts
-In order to be faster, QEMU does not check at every basic block if an
+In order to be faster, QEMU does not check at every basic block if a
hardware interrupt is pending. Instead, the user must asynchronously
call a specific function to tell that an interrupt is pending. This
function resets the chaining of the currently executing basic
@table @asis
@item [1]
-@url{http://citeseer.nj.nec.com/piumarta98optimizing.html}, Optimizing
-direct threaded code by selective inlining (1998) by Ian Piumarta, Fabio
-Riccardi.
+@url{http://bochs.sourceforge.net/}, the Bochs IA-32 Emulator Project,
+by Kevin Lawton et al.
@item [2]
-@url{http://developer.kde.org/~sewardj/}, Valgrind, an open-source
-memory debugger for x86-GNU/Linux, by Julian Seward.
+@url{http://www.valgrind.org/}, Valgrind, an open-source memory debugger
+for GNU/Linux.
@item [3]
-@url{http://bochs.sourceforge.net/}, the Bochs IA-32 Emulator Project,
-by Kevin Lawton et al.
+@url{http://ftp.dreamtime.org/pub/linux/Linux-Alpha/em86/v0.2/docs/em86.html},
+the EM86 x86 emulator on Alpha-Linux.
@item [4]
-@url{http://www.cs.rose-hulman.edu/~donaldlf/em86/index.html}, the EM86
-x86 emulator on Alpha-Linux.
-
-@item [5]
@url{http://www.usenix.org/publications/library/proceedings/usenix-nt97/@/full_papers/chernoff/chernoff.pdf},
DIGITAL FX!32: Running 32-Bit x86 Applications on Alpha NT, by Anton
Chernoff and Ray Hookway.
-@item [6]
-@url{http://www.willows.com/}, Windows API library emulation from
-Willows Software.
-
-@item [7]
+@item [5]
@url{http://user-mode-linux.sourceforge.net/},
The User-mode Linux Kernel.
-@item [8]
+@item [6]
@url{http://www.plex86.org/},
The new Plex86 project.
-@item [9]
+@item [7]
@url{http://www.vmware.com/},
The VMWare PC virtualizer.
-@item [10]
-@url{http://www.microsoft.com/windowsxp/virtualpc/},
+@item [8]
+@url{https://www.microsoft.com/download/details.aspx?id=3702},
The VirtualPC PC virtualizer.
-@item [11]
-@url{http://www.twoostwo.org/},
-The TwoOStwo PC virtualizer.
-
-@item [12]
+@item [9]
@url{http://virtualbox.org/},
The VirtualBox PC virtualizer.
-@item [13]
+@item [10]
@url{http://www.xen.org/},
The Xen hypervisor.
-@item [14]
-@url{http://kvm.qumranet.com/kvmwiki/Front_Page},
+@item [11]
+@url{http://www.linux-kvm.org/},
Kernel Based Virtual Machine (KVM).
-@item [15]
+@item [12]
@url{http://www.greensocs.com/projects/QEMUSystemC},
QEMU-SystemC, a hardware co-simulator.
projects / mirror_qemu.git / blobdiff