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qemu-tech.texi: Remove "QEMU compared to other emulators" section

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The "QEMU compared to other emulators" section of our documentation
hasn't been updated since 2015 (and parts of the text are even older).
We're clearly not very well placed to track the evolution of a
dozen other emulation projects, and an inaccurate or out of date
comparison doesn't serve anybody, so we're best off just removing
the whole documentation section.

If anybody cares strongly about maintaining a comparison page,
it's probably better to do that on the project's wiki where
we can update it more dynamically.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20190607152827.18003-3-peter.maydell@linaro.org
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Peter Maydell 2019-06-17 15:35:31 +01:00
parent 2f2c4e4731
commit 282d36b5e2
1 changed files with 0 additions and 107 deletions
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@ -161,57 +161,6 @@ may be created from overlay with minimal amount of hand-written code.
@end itemize
@node QEMU compared to other emulators
@section QEMU compared to other emulators
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.
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). 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 [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 [4]).
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 [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 [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
done except for some privileged instructions), it has the potential of
being faster than QEMU. The downside is that a complicated (and
potentially unsafe) host kernel patch is needed.
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 [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 Managed start up options
@section Managed start up options
@ -247,59 +196,3 @@ depend on an initialized machine, including but not limited to:
@item query-status
@item x-exit-preconfig
@end table
@node Bibliography
@section Bibliography
@table @asis
@item [1]
@url{http://bochs.sourceforge.net/}, the Bochs IA-32 Emulator Project,
by Kevin Lawton et al.
@item [2]
@url{http://www.valgrind.org/}, Valgrind, an open-source memory debugger
for GNU/Linux.
@item [3]
@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.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 [5]
@url{http://user-mode-linux.sourceforge.net/},
The User-mode Linux Kernel.
@item [6]
@url{http://www.plex86.org/},
The new Plex86 project.
@item [7]
@url{http://www.vmware.com/},
The VMWare PC virtualizer.
@item [8]
@url{https://www.microsoft.com/download/details.aspx?id=3702},
The VirtualPC PC virtualizer.
@item [9]
@url{http://virtualbox.org/},
The VirtualBox PC virtualizer.
@item [10]
@url{http://www.xen.org/},
The Xen hypervisor.
@item [11]
@url{http://www.linux-kvm.org/},
Kernel Based Virtual Machine (KVM).
@item [12]
@url{http://www.greensocs.com/projects/QEMUSystemC},
QEMU-SystemC, a hardware co-simulator.
@end table