mirror of
https://github.com/xemu-project/xemu.git
synced 2025-02-17 18:48:36 +00:00
ed4f49ba9b
The primary purpose of this change is to support programs compiled by GCC for the R5900 target and thereby run R5900 Linux distributions, for example Gentoo. GCC in version 7.3, by itself, by inspection of the GCC source code and inspection of the generated machine code, for the R5900 target, only emits two instructions that are specific to the R5900: the three- operand MULT and MULTU. GCC and libc also emit certain MIPS III instructions that are not part of the R5900 ISA. They are normally trapped and emulated by the Linux kernel, and therefore need to be treated accordingly by QEMU. A program compiled by GCC is taken to mean source code compiled by GCC under the restrictions above. One can, with the apparent limitations, with a bit of effort obtain a fully functioning operating system such as R5900 Gentoo. Strictly speaking, programs need not be compiled by GCC to make use of this change. Instructions and other facilities of the R5900 not implemented by this change are intended to signal provisional exceptions. One such example is the FPU that is not compliant with IEEE 754-1985 in system mode. It is therefore provisionally disabled. In user space the FPU is trapped and emulated by IEEE 754-1985 compliant software in the kernel, and this is handled accordingly by QEMU. Another example is the 93 multimedia instructions specific to the R5900 that generate provisional reserved instruction exception signals. One of the benefits of running a Linux distribution under QEMU is that programs can be compiled with a native compiler, where the host and target are the same, as opposed to a cross-compiler, where they are not the same. This is especially important in cases where the target hardware does not have the resources to run a native compiler. Problems with cross-compilation are often related to host and target differences in integer sizes, pointer sizes, endianness, machine code, ABI, etc. Sometimes cross-compilation is not even supported by the build script for a given package. One effective way to avoid those problems is to replace the cross-compiler with a native compiler. This change of compilation methods does not resolve the inherent problems with cross-compilation. The native compiler naturally replaces the cross-compiler, because one typically uses one or the other, and preferably the native compiler when the circumstances admit this. The native compiler is also a good test case for the R5900 QEMU user mode. Additionally, Gentoo is well- known for compiling and installing its packages from sources. This change has been tested with Gentoo compiled for R5900, including native compilation of several packages under QEMU. Reviewed-by: Aleksandar Markovic <amarkovic@wavecomp.com> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Signed-off-by: Fredrik Noring <noring@nocrew.org> Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>
QEMU README
===========
QEMU is a generic and open source machine & userspace emulator and
virtualizer.
QEMU is capable of emulating a complete machine in software without any
need for hardware virtualization support. By using dynamic translation,
it achieves very good performance. QEMU can also integrate with the Xen
and KVM hypervisors to provide emulated hardware while allowing the
hypervisor to manage the CPU. With hypervisor support, QEMU can achieve
near native performance for CPUs. When QEMU emulates CPUs directly it is
capable of running operating systems made for one machine (e.g. an ARMv7
board) on a different machine (e.g. an x86_64 PC board).
QEMU is also capable of providing userspace API virtualization for Linux
and BSD kernel interfaces. This allows binaries compiled against one
architecture ABI (e.g. the Linux PPC64 ABI) to be run on a host using a
different architecture ABI (e.g. the Linux x86_64 ABI). This does not
involve any hardware emulation, simply CPU and syscall emulation.
QEMU aims to fit into a variety of use cases. It can be invoked directly
by users wishing to have full control over its behaviour and settings.
It also aims to facilitate integration into higher level management
layers, by providing a stable command line interface and monitor API.
It is commonly invoked indirectly via the libvirt library when using
open source applications such as oVirt, OpenStack and virt-manager.
QEMU as a whole is released under the GNU General Public License,
version 2. For full licensing details, consult the LICENSE file.
Building
========
QEMU is multi-platform software intended to be buildable on all modern
Linux platforms, OS-X, Win32 (via the Mingw64 toolchain) and a variety
of other UNIX targets. The simple steps to build QEMU are:
mkdir build
cd build
../configure
make
Additional information can also be found online via the QEMU website:
https://qemu.org/Hosts/Linux
https://qemu.org/Hosts/Mac
https://qemu.org/Hosts/W32
Submitting patches
==================
The QEMU source code is maintained under the GIT version control system.
git clone git://git.qemu.org/qemu.git
When submitting patches, one common approach is to use 'git
format-patch' and/or 'git send-email' to format & send the mail to the
qemu-devel@nongnu.org mailing list. All patches submitted must contain
a 'Signed-off-by' line from the author. Patches should follow the
guidelines set out in the HACKING and CODING_STYLE files.
Additional information on submitting patches can be found online via
the QEMU website
https://qemu.org/Contribute/SubmitAPatch
https://qemu.org/Contribute/TrivialPatches
The QEMU website is also maintained under source control.
git clone git://git.qemu.org/qemu-web.git
https://www.qemu.org/2017/02/04/the-new-qemu-website-is-up/
A 'git-publish' utility was created to make above process less
cumbersome, and is highly recommended for making regular contributions,
or even just for sending consecutive patch series revisions. It also
requires a working 'git send-email' setup, and by default doesn't
automate everything, so you may want to go through the above steps
manually for once.
For installation instructions, please go to
https://github.com/stefanha/git-publish
The workflow with 'git-publish' is:
$ git checkout master -b my-feature
$ # work on new commits, add your 'Signed-off-by' lines to each
$ git publish
Your patch series will be sent and tagged as my-feature-v1 if you need to refer
back to it in the future.
Sending v2:
$ git checkout my-feature # same topic branch
$ # making changes to the commits (using 'git rebase', for example)
$ git publish
Your patch series will be sent with 'v2' tag in the subject and the git tip
will be tagged as my-feature-v2.
Bug reporting
=============
The QEMU project uses Launchpad as its primary upstream bug tracker. Bugs
found when running code built from QEMU git or upstream released sources
should be reported via:
https://bugs.launchpad.net/qemu/
If using QEMU via an operating system vendor pre-built binary package, it
is preferable to report bugs to the vendor's own bug tracker first. If
the bug is also known to affect latest upstream code, it can also be
reported via launchpad.
For additional information on bug reporting consult:
https://qemu.org/Contribute/ReportABug
Contact
=======
The QEMU community can be contacted in a number of ways, with the two
main methods being email and IRC
- qemu-devel@nongnu.org
https://lists.nongnu.org/mailman/listinfo/qemu-devel
- #qemu on irc.oftc.net
Information on additional methods of contacting the community can be
found online via the QEMU website:
https://qemu.org/Contribute/StartHere
-- End